ACE Level

See Angiotensin-Converting Enzyme (ACE) level

Acetone (Serum or Plasma)

• 
  

  Normal: negative

  
  
• 
  

  Elevated in: diabetic ketoacidosis (DKA), starvation, isopropanol ingestion

Acetylcholine Receptor (AChR) Antibody

• 
  

  Normal: <0.03 nmol/L

  
  
• 
  

  Elevated in: myasthenia gravis. Changes in AChR concentration correlate with the clinical severity of myasthenia gravis after therapy and during therapy with prednisone and immunosuppressants. False-positive AChR antibody results may be found in patients with Eaton-Lambert syndrome.

Acid Phosphatase (Serum)

• 
  

  Normal range: enzymatic, prostatic 0 to 5.5 U/L; enzymatic, total 2 to 12 U/L

  
  
• 
  

  Elevated in: carcinoma of prostate, other neoplasms (breast, bone), Paget’s disease of bone, hemolysis, multiple myeloma, osteogenesis imperfecta, malignant invasion of bone, Gaucher’s disease, myeloproliferative disorders, prostatic palpation or surgery, hyperparathyroidism, liver disease, chronic renal failure, idiopathic thrombocytopenic purpura (ITP)

Acid Serum Test

• 
  

  See Ham Test

Activated Clotting Time (ACT)

• 
  

  Normal: This test is used to determine the dose of protamine sulfate to reverse the effect of heparin as an anticoagulant during angioplasty, cardiac surgery, and hemodialysis. The accepted goal during cardiopulmonary bypass surgery is usually 400 to 500 seconds.

Activated Partial Thromboplastin Time (aPTT)

See Partial Thromboplastin Time (PTT), Activated Partial Thromboplastin Time (aPTT)

Adrenocorticotropic Hormone (ACTH)

• 
  

  Normal range: 9 to 52 pg/mL

  
  
• 
  

  Elevated in: Addison’s disease, ectopic ACTH-producing tumors, congenital adrenal hyperplasia, Nelson’s syndrome, pituitary-dependent Cushing’s disease

  
  
• 
  

  Decreased in: secondary adrenocortical insufficiency, hypopituitarism, adrenal adenoma or adrenal carcinoma

Alanine Aminopeptidase

• 
  

  Normal range:

  
  
  
  
  • 
    

    Male: 1.11 to 1.71 mcg/mL

    
    
  • 
    

    Female: 0.96 to 1.52 mcg/mL

  
  
  
  
• 
  

  Elevated in: liver or pancreatic disease, ethanol ingestion, use of oral contraceptives, malignancy, tobacco use, pregnancy

  
  
• 
  

  Decreased in: abortion

Alanine Aminotransferase (ALT, formerly serum glutamic-pyruvic transaminase [SGPT])

• 
  

  Normal range:

  
  
  
  
  • 
    

    Male: 10 to 40 U/L

    
    
  • 
    

    Female: 8 to 35 U/L

  
  
  
  
• 
  

  Elevated in: liver disease (e.g., hepatitis, cirrhosis, Reye’s syndrome), alcohol abuse, drug use (e.g., acetaminophen, statins, nonsteroidal antiinflammatory drugs [NSAIDs], antibiotics, anabolic steroids, narcotics, heparin, labetalol, amiodarone, chlorpromazine, phenytoin), hepatic congestion, infectious mononucleosis, liver metastases, myocardial infarction [MI], myocarditis, severe muscle trauma, dermatomyositis or polymyositis, muscular dystrophy, malignancy, renal and pulmonary infarction, convulsions, eclampsia, dehydration (relative increase), ingestion of Chinese herbs

  
  
• 
  

  Decreased in: azotemia, advanced malnutrition, chronic renal dialysis, chronic alcoholic liver disease, metronidazole use

Albumin (Serum)

• 
  

  Normal range: 4 to 6 g/dL

  
  
• 
  

  Elevated in: dehydration (relative increase), intravenous albumin infusion

  
  
• 
  

  Decreased in: liver disease, nephrotic syndrome, poor nutritional status, rapid intravenous hydration, protein-losing enteropathies (inflammatory bowel disease), severe burns, neoplasia, chronic inflammatory diseases, pregnancy, prolonged immobilization, lymphomas, hypervitaminosis A, chronic glomerulonephritis

Alcohol Dehydrogenase

• 
  

  Normal range: 0 to 7 U/L

  
  
• 
  

  Elevated in: drug-induced hepatocellular damage, obstructive jaundice, malignancy, inflammation, infection

Aldolase (Serum)

• 
  

  Normal range: 0 to 6 U/L

  
  
• 
  

  Elevated in: rhabdomyolysis, dermatomyositis or polymyositis, trichinosis, acute hepatitis and other liver diseases, muscular dystrophy, myocardial infarction, prostatic carcinoma, hemorrhagic pancreatitis, gangrene, delirium tremens, burns

  
  
• 
  

  Decreased in: loss of muscle mass, late stages of muscular dystrophy

Aldosterone (Plasma)

• 
  

  Normal range:

  
  
  
  
  • 
    

    Adult supine: 3 to 16 ng/dL

    
    
  • 
    

    Adult upright: 7 to 30 ng/dL

    
    
  • 
    

    Adrenal vein: 200 to 800 ng/dL

  
  
  
  
• 
  

  Elevated in: aldosterone-secreting adenoma, bilateral adrenal hyperplasia, secondary aldosteronism (diuretics, congestive heart failure, laxatives, nephritic syndrome, cirrhosis with ascites, Bartter’s syndrome, pregnancy, starvation). Table 2.1 summarizes use of plasma renin and plasma aldosterone values in the evaluation of hypokalemia or hyperkalemia.

  
  
  
  

  TABLE 2.1

  
  

  Use of Plasma Renin and Plasma Aldosterone Values to Assess the Basis of Hypokalemia or Hyperkalemia

  
  

  From Skorecki K, Chertow GM, Marsden PA, et al: Brenner and Rector’s the kidney, ed 10, Philadelphia, Elsevier, 2016.

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  	Renin	Aldosterone
  Lesions That Cause Hypokalemia
  Adrenal gland:
  Primary hyperaldosteronism	Low	High
  Glucocorticoid-remediable hyperaldosteronism	Low	High
  Kidney:
  Renal artery stenosis	High	High
  Malignant hypertension	High	High
  Renin-secreting tumor	High	High
  Liddle’s syndrome	Low	Low
  Disorders involving 11β-hydroxysteroid dehydrogenase (HSDH)	Low	Low
  Lesions That Cause Hyperkalemia
  Adrenal gland:
  Addison’s disease	High	Low
  Kidney:
  Pseudohypoaldosteronism type 1	High	High
  Hyporeninemic hypoaldosteronism	Low	Low

   
  
  
  
  
• 
  

  Decreased in: Addison’s disease, renin deficiency, Turner’s syndrome, diabetes mellitus, isolated aldosterone deficiency, postacute alcohol intoxication (hangover phase)

Alkaline Phosphatase (Serum)

• 
  

  Normal range: 30 to 120 U/L

  
  
• 
  

  Elevated in: biliary obstruction, cirrhosis (particularly primary biliary cirrhosis), liver disease (hepatitis, infiltrative liver diseases, fatty metamorphosis), Paget’s disease of bone, osteitis deformans, rickets, osteomalacia, hypervitaminosis D, hyperparathyroidism, hyperthyroidism, ulcerative colitis, bowel perforation, bone metastases, healing fractures, bone neoplasms, acromegaly, infectious mononucleosis, cytomegalovirus infections, sepsis, pulmonary infarction, hypernephroma, leukemia, myelofibrosis, multiple myeloma, drug therapy (estrogens, albumin, erythromycin and other antibiotics, cholestasis-producing drugs [phenothiazines]), pregnancy, puberty, postmenopausal females. Fig. 2.1 illustrates evaluation of isolated elevation of serum alkaline phosphatase.

  
  

  
  

  
  

  

  
  

  
  

  Evaluation of an isolated elevation of the serum alkaline phosphatase level. ACE, angiotensin-converting enzyme; ALP, alkaline phosphatase; AMA, antimitochondrial antibodies; 5 ′ NT , 5′ nucleotidase; ERCP, endoscopic retrograde cholangiopancreatography; MRCP, magnetic resonance cholangiopancreatography; RUQ, right upper quadrant.

  
  

  From Feldman M, Friedman LS, Brandt LJ: Sleisenger and Fordtran’s gastrointestinal and liver disease , ed 10, Philadelphia, Elsevier, 2016.

  
  
  
  
• 
  

  Decreased in: hypothyroidism, pernicious anemia, hypophosphatemia, hypervitaminosis D, malnutrition

Alpha-1-Antitrypsin (Serum)

• 
  

  Normal range: 110 to 140 mg/dL

  
  
• 
  

  Decreased in: homozygous or heterozygous deficiency

Alpha-1-Fetoprotein (Serum)

• 
  

  Normal range: 0 to 20 ng/mL

  
  
• 
  

  Elevated in: hepatocellular carcinoma (usual values >1000 ng/mL), germinal neoplasms (testis, ovary, mediastinum, retroperitoneum), liver disease (alcoholic cirrhosis, acute hepatitis, chronic active hepatitis), fetal anencephaly, spina bifida, basal cell carcinoma, breast carcinoma, pancreatic carcinoma, gastric carcinoma, retinoblastoma, esophageal atresia

ALT

See Alanine Aminotransferase

Aluminum (Serum)

• 
  

  Normal range: 0 to 6 ng/mL

  
  
• 
  

  Elevated in: chronic renal failure on dialysis, parenteral nutrition, industrial exposure

AMA

See Mitochondrial Antibody

Amebiasis Serologic Test

• 
  

  Test description: Test is used to support diagnosis of amebiasis caused by Entamoeba histolytica. Serum acute and convalescent titers are drawn 1 to 3 weeks apart. A fourfold increase in titer is the most indicative result.

Aminolevulinic Acid (d-ALA) (24-Hour Urine Collection)

• 
  

  Normal range: 1.5 to 7.5 md/day

  
  
• 
  

  Elevated in: acute porphyrias, lead poisoning, diabetic ketoacidosis, pregnancy, use of anticonvulsant drugs, hereditary tyrosinemia

  
  
• 
  

  Decreased in: alcoholic liver disease

Ammonia (Serum)

• 
  

  Normal range:

  
  
  
  
  • 
    

    Adults: 15 to 45 mcg/dL

    
    
  • 
    

    Children: 29 to 70 mcg/dL

  
  
  
  
• 
  

  Elevated in: hepatic failure, hepatic encephalopathy, Reye’s syndrome, portacaval shunt, drug therapy (diuretics, polymyxin B, methicillin)

  
  
• 
  

  Decreased in: drug therapy (neomycin, lactulose), renal failure

Amylase (Serum)

• 
  

  Normal range: 0 to 130 U/L

  
  
• 
  

  Elevated in: acute pancreatitis, macroamylasemia, salivary gland inflammation, mumps, pancreatic neoplasm, abscess, pseudocyst, ascites, perforated peptic ulcer, intestinal obstruction, intestinal infarction, acute cholecystitis, appendicitis, ruptured ectopic pregnancy, peritonitis, burns, diabetic ketoacidosis, renal insufficiency, drug use (morphine), carcinomatosis of lung, esophagus, ovary, acute ethanol ingestion, prostate tumors, post–endoscopic retrograde cholangiopancreatography, bulimia, anorexia nervosa

  
  
• 
  

  Decreased in: advanced chronic pancreatitis, hepatic necrosis, cystic fibrosis

Amylase, Urine

See Urine Amylase

Amyloid A Protein (Serum)

• 
  

  Normal: <10 mcg/mL

  
  
• 
  

  Elevated in: inflammatory disorders (acute phase-reacting protein), infections, acute coronary syndrome, malignancies

ANA

See Antinuclear Antibody

ANCA

See Antineutrophil Cytoplasmic Antibody

Androstenedione (Serum)

• 
  

  Normal range:

  
  
  
  
  • 
    

    Male: 75 to 205 ng/dL

    
    
  • 
    

    Female: 85 to 275 ng/dL

  
  
  
  
• 
  

  Elevated in: congenital adrenal hyperplasia, polycystic ovary syndrome, ectopic adrenocorticotropic hormone–producing tumor, Cushing’s syndrome, hirsutism, hyperplasia of ovarian stroma, ovarian neoplasm

  
  
• 
  

  Decreased in: ovarian failure, adrenal failure, sickle cell anemia

Angiotensin II

• 
  

  Normal range: 10 to 60 pg/mL

  
  
• 
  

  Elevated in: hypertension, congestive heart failure, cirrhosis, renin-secreting renal tumor, volume depletion

  
  
• 
  

  Decreased in: angiotensin-converting enzyme inhibitor drugs, angiotensin II receptor blocker drugs, primary aldosteronism, Cushing’s syndrome

Angiotensin-Converting Enzyme (ACE) Level

• 
  

  Normal: <40 nmol/mL/min

  
  
• 
  

  Elevated in: sarcoidosis, primary biliary cirrhosis, alcoholic liver disease, hyperthyroidism, hyperparathyroidism, diabetes mellitus, amyloidosis, multiple myeloma, lung disease (asbestosis, silicosis, berylliosis, allergic alveolitis, coccidioidomycosis), Gaucher’s disease, leprosy

  
  
• 
  

  Decreased in: ACE inhibitor therapy

ANH

See Atrial Natriuretic Hormone

Anion Gap

• 
  

  Normal range: 9 to 14 mEq/L. The calculation of anion gap is described in Table 2.2 .

  
  
  
  

  TABLE 2.2

  
  

  The Anion Gap

  
  

  From Skorecki K, Chertow GM, Marsden PA, et al: Brenner and Rector’s the kidney , ed 10, Philadelphia, Elsevier, 2016.

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Anion Gap = Na + − (Cl − + HCO 3 − ) = 9 ± 3 mEq/L (Assumes Normal [Albumin]) ∗
  Decreased Anion Gap	Increased Anion Gap
  Increased Cations (Not Na + )	Increased Anions (Not Cl − or HCO 3 − )
  ↑ Ca 2+ , Mg 2+	↑ Albumin
  ↑ Li +	Alkalosis
  ↑ Immunoglobulin G	↑ Inorganic anions Phosphate Sulfate
  Decreased Anions (Not Cl − or HCO 3 − )
  Hypoalbuminemia ∗ Acidosis Laboratory Error Hyperviscosity Bromism	↑ Organic anions l -Lactate d -Lactate Ketones Uremic ↑ Exogenously supplied anions Toxins Salicylate Paraldehyde Ethylene glycol Propylene glycol Methanol Toluene Pyroglutamic acid (5-oxoprolene)
  	↑ Unidentified anions Other toxins Uremic Hyperosmolar, nonketotic states Myoglobinuric acute kidney injury
  	Decreased Cations (Not Na + )
  	↓ Ca 2+ , Mg 2+

   
  

  ∗ For each decline in albumin by 1 g/dL from normal (4.5 g/dL), the anion gap decreases by 2.5 mEq/L.

  
  
  
  
• 
  

  Elevated in: lactic acidosis, ketoacidosis (diabetic ketoacidosis, alcoholic starvation), uremia (chronic renal failure), ingestion of toxins (paraldehyde, methanol, salicylates, ethylene glycol), hyperosmolar nonketotic coma, antibiotic therapy (carbenicillin)

  
  
• 
  

  Decreased in: hypoalbuminemia, severe hypermagnesemia, immunoglobulin G myeloma, lithium toxicity, laboratory error (falsely decreased sodium or overestimation of bicarbonate or chloride), hypercalcemia of parathyroid origin, antibiotic therapy (e.g., polymyxin)

Anticardiolipin Antibody (ACA)

• 
  

  Normal: negative. Test includes detection of immunoglobulin (Ig) G, IgM, and IgA antibody to phospholipid, cardiolipin.

  
  
• 
  

  Present in: antiphospholipid antibody syndrome, chronic hepatitis C

Anticoagulant

See Circulating Anticoagulant (Antiphospholipid Antibody, Lupus Anticoagulant)

Antidiuretic Hormone

• 
  

  Normal range: mOsm/kg 295 to 300; 4 to 12 pg/mL

  
  
• 
  

  Elevated in: syndrome of inappropriate antidiuretic hormone, antipsychotic medication therapy, ectopic antidiuretic hormone from systemic neoplasm, Guillain-Barré, central nervous system infections, brain tumors, nephrogenic diabetes insipidus

  
  
• 
  

  Decreased in: central diabetes insipidus, nephritic syndrome, psychogenic polydipsia, demeclocycline, lithium therapy, phenytoin use, alcohol use

Anti-DNA

• 
  

  Normal: absent

  
  
• 
  

  Present in: systemic lupus erythematosus, chronic active hepatitis, infectious mononucleosis, biliary cirrhosis

Anti-ds DNA

• 
  

  Normal: <25 U

  
  
• 
  

  Elevated in: systemic lupus erythematosus

Anti-Globulin Test, Direct

See Direct Antiglobulin Test

Anti-Globulin Test, Indirect

See Coombs, Indirect

Antiglomerular Basement Antibody

See Glomerular Basement Membrane Antibody

Anti-HCV

See Hepatitis C Antibody

Antihistone

• 
  

  Normal: <1 U

  
  
• 
  

  Elevated in: drug-induced lupus erythematosus

Antimitochondrial Antibody (AMA)

• 
  

  Normal range: <1:20 titer

  
  
• 
  

  Elevated in: primary biliary cirrhosis (85%–95%), chronic active hepatitis (25%–30%), cryptogenic cirrhosis (25%–30%)

Antineutrophil Cytoplasmic Antibody (ANCA)

• 
  

  Positive test:

  
  
  
  
  • 
    

    Cytoplasmic pattern (cANCA): positive in granulomatosis with polyangiitis (Wegener’s granulomatosis)

    
    
  • 
    

    Perinuclear pattern (pANCA): positive in inflammatory bowel disease, primary biliary cirrhosis, primary sclerosing cholangitis, autoimmune chronic active hepatitis, crescentic glomerulonephritis

  
  

Antinuclear Antibody (ANA)

• 
  

  Normal: <1:20 titer

  
  
• 
  

  Positive test: systemic lupus erythematosus (more significant if titer > 1:160), drug therapy (phenytoin, ethosuximide, primidone, methyldopa, hydralazine, carbamazepine, penicillin, procainamide, chlorpromazine, griseofulvin, thiazides), chronic active hepatitis, age older than 60 years (particularly age older than 80), rheumatoid arthritis, scleroderma, mixed connective tissue disease, necrotizing vasculitis, Sjögren’s syndrome

Fig. 2.2 describes diagnostic tests and diagnoses to consider from ANA patterns.

Patterns of immunofluorescent staining of antinuclear antibodies and the diseases with which they are associated. SLE, systemic lupus erythematosus.

From Pagana KD, Pagana TJ: Mosby’s diagnostic and laboratory test reference, ed 8, St. Louis, Mosby, 2006.

Antiphospholipid Antibody

See Lupus Anticoagulant (LA) Test

Anti-RNP Antibody

See Extractable Nuclear Antigen

Anti-Scl-70

• 
  

  Normal: absent

  
  
• 
  

  Elevated in: scleroderma

Anti-Smith (Anti-Sm) Antibody

See Extractable Nuclear Antigen

Anti-Smooth Muscle Antibody

See Smooth Muscle Antibody

Antistreptolysin O Titer (Streptozyme, ASLO Titer)

• 
  

  Normal for adults: <160 Todd units

  
  
• 
  

  Elevated in: streptococcal upper airway infection, acute rheumatic fever, acute glomerulonephritis, increased levels of β-lipoprotein (false-positive ASLO test)

  
  
• 
  

  Note: A fourfold increase in titer between acute and convalescent specimens is diagnostic of streptococcal upper airway infection regardless of the initial titer.

Antithrombin III

• 
  

  Normal range: 81% to 120% of normal activity; 17 to 30 mg/dL

  
  
• 
  

  Elevated in: warfarin drug therapy, post–myocardial infarction

  
  
• 
  

  Decreased in: hereditary deficiency of antithrombin III, disseminated intravascular coagulation, pulmonary embolism, cirrhosis, thrombolytic therapy, chronic liver failure, postsurgery, third trimester of pregnancy, oral contraceptive use, nephrotic syndrome, intravenous heparin therapy >3 days, sepsis, acute leukemia, carcinoma, thrombophlebitis

Apolipoprotein A-1 (Apo A-1)

• 
  

  Normal: recommended >120 mg/dL

  
  
• 
  

  Elevated in: familial hyperalphalipoproteinemia, statins, niacin, estrogens, weight loss, familial cholesteryl ester transfer protein deficiency

  
  
• 
  

  Decreased in: familial hypoalphalipoproteinemia, Tangier disease, diuretic use, androgens, cigarette smoking, hepatocellular disorders, chronic renal failure, nephritic syndrome, coronary heart disease, cholestasis

Apolipoprotein B (Apo B)

• 
  

  Normal: desirable <100 mg/dL, high risk >120 mg/dL

  
  
• 
  

  Elevated in: high-saturated-fat diet, high-cholesterol diet, hyper-apobetalipoproteinemia, familial combined hyperlipidemia, anabolic steroids, diuretic use, beta blocker therapy, corticosteroid use, progestin use, diabetes, hypothyroidism, chronic renal failure, liver disease, Cushing’s syndrome, coronary heart disease

  
  
• 
  

  Decreased in: statin therapy, niacin, low-cholesterol diet, malnutrition, abetalipoproteinemia, hypobetalipoproteinemia, hyperthyroidism

Arterial Blood Gases

• 
  

  Normal range:

  
  
  
  
  • 
    

    P o ₂ : 75 to 100 mm Hg

    
    
  • 
    

    P co ₂ : 35 to 45 mm Hg

    
    
  • 
    

    <SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='HCO−3′>HCO−3HCO−3
    HCO − 3
    : 24 to 28 mEq/L

    
    
  • 
    

    pH: 7.35-7.45

  
  
  
  
• 
  

  Abnormal values: Acid-base disturbances (see following). Table 2.3 summarizes acid-base abnormalities and appropriate compensatory responses.

  
  
  
  

  TABLE 2.3

  
  

  Acid-Base Abnormalities and Appropriate Compensatory Responses for Simple Disorders

  
  

  Adapted from Bidani A, Tauzon DM, Heming TA: Regulation of whole body acid-base balance. In DuBose TD, Hamm LL, [eds]: Acid-base and electrolyte disorders: a companion to Brenner and Rector’s the kidney , Philadelphia, 2002, Saunders, pp. 1-2. From Skorecki K, Chertow GM, Marsden PA, et al: Brenner and Rector’s the kidney , ed 10, Philadelphia, Elsevier, 2016.

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Primary Acid-Base Disorders	Primary Defect	Effect on pH	Compensatory Response	Expected Range of Compensation	Limits of Compensation
  Respiratory acidosis	Alveolar hypoventilation (↑ P co 2 )	↓	↑ Renal HCO 3 − reabsorption (HCO 3 − ↑)	Acute Δ [HCO 3 − ] = +1 mEq/L for each ↑ Δ PCO 2 of 10 mm Hg	[HCO 3 − ] = 38 mEq/L
  				Chronic Δ [HCO 3 − ] = +4 mEq/L for each ↑ Δ PCO 2 of 10 mm Hg	[HCO 3 − ] = 45 mEq/L
  Respiratory alkalosis	Alveolar hyperventilation (↓ P co 2 )	↑	↓ Renal HCO 3 − reabsorption (HCO 3 − ↓)	Acute Δ [HCO 3 − ] = −2 mEq/L for each ↓ Δ PCO 2 of 10 mm Hg	[HCO 3 − ] = 18 mEq/L
  				Chronic Δ [HCO 3 − ] = −5 mEq/L for each ↓ Δ PCO 2 of 10 mm Hg	[HCO 3 − ] = 15 mEq/L
  Metabolic acidosis	Loss of HCO 3 − or gain of H + (↓HCO 3 − )	↓	Alveolar hyperventilation to ↑ pulmonary CO 2 excretion (↓P co 2 )	P co 2 = 1.5[HCO 3 − ] + 8 ± 2 P co 2 = last 2 digits of pH × 100 P co 2 = 15 + [HCO 3 − ]	P co 2 = 15 mm Hg
  Metabolic alkalosis	Gain of HCO 3 Δ or loss of H + (↑HCO 3 − )	↑	Alveolar hypoventilation to ↓ pulmonary CO 2 excretion (↑P co 2 )	P co 2 = +0.6 mm Hg for Δ [HCO 3 − ] of 1 mEq/L P co 2 = 15 + [HCO 3 − ]	P co 2 = 55 mm Hg

   
  

  P co ₂ , carbon dioxide pressure.
  
  

• 1.
  

  Metabolic acidosis

  
  
  
  
  • a.
    

    Metabolic acidosis with increased anion gap (AG acidosis)

    
    
    
    
    • i.
      

      Lactic acidosis

      
      
    • ii.
      

      Ketoacidosis (diabetes mellitus, alcoholic ketoacidosis)

      
      
    • iii.
      

      Uremia (chronic renal failure)

      
      
    • iv.
      

      Ingestion of toxins (paraldehyde, methanol, salicylate, ethylene glycol)

      
      
    • v.
      

      High-fat diet (mild acidosis)

      
      
    • vi.
      

      Metabolic acidosis with normal AG (hyperchloremic acidosis)

      
      
    • vii.
      

      Renal tubular acidosis (including acidosis of aldosterone deficiency)

      
      
    • viii.
      

      Intestinal loss of <SPAN role=presentation tabIndex=0 id=MathJax-Element-2-Frame class=MathJax style="POSITION: relative" data-mathml='HCO−3′>HCO−3HCO−3
      HCO − 3
      (diarrhea, pancreatic fistula)

      
      
    • ix.
      

      Carbonic anhydrase inhibitors (e.g., acetazolamide)

      
      
    • x.
      

      Dilutional acidosis (as a result of rapid infusion of bicarbonate-free isotonic saline)

      
      
    • xi.
      

      Ingestion of exogenous acids (ammonium chloride, methionine, cystine, calcium chloride)

      
      
    • xii.
      

      Ileostomy

      
      
    • xiii.
      

      Ureterosigmoidostomy

      
      
    • xiv.
      

      Drug therapy: amiloride, triamterene, spironolactone, beta blockers

    
    

  
  
  
  
• 2.
  

  Respiratory acidosis

  
  
  
  
  • a.
    

    Pulmonary disease (chronic obstructive pulmonary disease, severe pneumonia, pulmonary edema, interstitial fibrosis)

    
    
  • b.
    

    Airway obstruction (foreign body, severe bronchospasm, laryngospasm)

    
    
  • c.
    

    Thoracic cage disorders (pneumothorax, flail chest, kyphoscoliosis)

    
    
  • d.
    

    Defects in muscles of respiration (myasthenia gravis, hypokalemia, muscular dystrophy)

    
    
  • e.
    

    Defects in peripheral nervous system (amyotrophic lateral sclerosis, poliomyelitis, Guillain-Barré syndrome, botulism, tetanus, organophosphate poisoning, spinal cord injury)

    
    
  • f.
    

    Depression of respiratory center (anesthesia, narcotics, sedatives, vertebral artery embolism or thrombosis, increased intracranial pressure)

    
    
  • g.
    

    Failure of mechanical ventilator

  
  
  
  
• 3.
  

  Metabolic alkalosis. Metabolic alkalosis is divided into chloride-responsive (urinary chloride <15 mEq/L) and chloride-resistant forms (urinary chloride level >15 mEq/L).

  
  
  
  
  • a.
    

    Chloride-responsive

    
    
    
    
    • i.
      

      Vomiting

      
      
    • ii.
      

      Nasogastric suction

      
      
    • iii.
      

      Diuretics

      
      
    • iv.
      

      Posthypercapnic alkalosis

      
      
    • v.
      

      Stool losses (laxative abuse, cystic fibrosis, villous adenoma)

      
      
    • vi.
      

      Massive blood transfusion

      
      
    • vii.
      

      Exogenous alkali administration

    
    
    
    
  • b.
    

    Chloride-resistant

    
    
    
    
    • i.
      

      Hyperadrenocorticoid states (Cushing’s syndrome, primary hyperaldosteronism, secondary mineralocorticoidism [licorice ingestion, chewing tobacco use])

      
      
    • ii.
      

      Hypomagnesemia

      
      
    • iii.
      

      Hypokalemia

      
      
    • iv.
      

      Bartter’s syndrome

    
    

  
  
  
  
• 4.
  

  Respiratory alkalosis

  
  
  
  
  • a.
    

    Hypoxemia (pneumonia, pulmonary embolism, atelectasis, high-altitude living)

    
    
  • b.
    

    Drugs (salicylates, xanthines, progesterone, epinephrine, thyroxine, nicotine)

    
    
  • c.
    

    Central nervous system disorders (tumor, cerebrovascular accident, trauma, infections)

    
    
  • d.
    

    Psychogenic hyperventilation (anxiety, hysteria)

    
    
  • e.
    

    Hepatic encephalopathy

    
    
  • f.
    

    Gram-negative sepsis

    
    
  • g.
    

    Hyponatremia

    
    
  • h.
    

    Sudden recovery from metabolic acidosis

    
    
  • i.
    

    Assisted ventilation

  
  

Arthrocentesis Fluid

• 
  

  Interpretation of results:

• 1.
  

  Color: Normally it is clear or pale yellow; cloudiness indicates inflammatory process or presence of crystals, cell debris, fibrin, or triglycerides.

  
  
• 2.
  

  Viscosity: Normally it has a high viscosity because of hyaluronate; when fluid is placed on a slide, it can be stretched to a string greater than 2 cm in length before separating (low viscosity indicates breakdown of hyaluronate [lysosomal enzymes from leukocytes] or the presence of edema fluid).

  
  
• 3.
  

  Mucin clot: Add 1 mL of fluid to 5 mL of a 5% acetic acid solution and allow 1 minute for the clot to form; a firm clot (does not fragment on shaking) is normal and indicates the presence of large molecules of hyaluronic acid (this test is nonspecific and infrequently done).

  
  
• 4.
  

  Glucose: Normally glucose approximately equals serum glucose level; a difference of more than 40 mg/dL is suggestive of infection.

  
  
• 5.
  

  Protein: Total protein concentration is less than 2.5 g/dL in the normal synovial fluid; it is elevated in inflammatory and septic arthritis.

  
  
• 6.
  

  Microscopic examination for crystals

  
  
  
  
  • a.
    

    Gout: monosodium urate crystals

    
    
  • b.
    

    Pseudogout: calcium pyrophosphate dihydrate crystals

  
  

Table 2.4 describes synovial fluid findings in common disorders.

ASLO Titer

See Antistreptolysin O Titer

Aspartate Aminotransferase (AST, Serum Glutamic Oxaloacetic Transaminase [SGOT])

• 
  

  Normal range: 0 to 35 U/L

  
  
• 
  

  Elevated in: liver disease (hepatitis, hemochromatosis, cirrhosis, Reye’s syndrome, Wilson’s disease), alcohol abuse, drug therapy (acetaminophen, statins, nonsteroidal antiinflammatory drugs, angiotensin-converting enzyme inhibitors, heparin, labetalol, phenytoin, amiodarone, chlorpromazine), hepatic congestion, infec tious mononucleosis, myocardial infarction, myocarditis, severe muscle trauma, dermatomyositis and polymyositis, muscular dystrophy, malignancy, renal and pulmonary infarction, convulsions, eclampsia

  
  
• 
  

  Decreased in: uremia, vitamin B ₆ deficiency

Atrial Natriuretic Hormone (ANH)

• 
  

  Normal range: 20 to 77 pg/mL

  
  
• 
  

  Elevated in: congestive heart failure, volume overload, cardiovascular disease with high filling pressure

  
  
• 
  

  Decreased with: alpha blocker use

Basophil Count

• 
  

  Normal range: 0.4% to 1% of total white blood cells; 40 to 100/mm ³

  
  
• 
  

  Elevated in: inflammatory processes, leukemia, polycythemia vera, Hodgkin’s lymphoma, hemolytic anemia, after splenectomy, myeloid metaplasia, myxedema

  
  
• 
  

  Decreased in: stress, hypersensitivity reaction, steroids, pregnancy, hyperthyroidism

Bicarbonate

• 
  

  Normal range:

  
  
  
  
  • 
    

    Arterial: 21 to 28 mEq/L

    
    
  • 
    

    Venous: 22 to 29 mEq/L

  
  
  
  
• 
  

  Elevated in: metabolic alkalosis, compensated respiratory acidosis, diuretics, corticosteroids, laxative abuse

  
  
• 
  

  Decreased in: metabolic acidosis; compensated respiratory alkalosis; acetazolamide, cyclosporine, or cholestyramine use; methanol or ethylene glycol poisoning

Bile Acid Breath Test

• 
  

  Normal: The test determines the radioactivity of ¹⁴ CO ₂ in breath samples at 2 and 4 hours.

  
  
  
  
  • 
    

    2 hours after dose: 0.11 ± 0.14

    
    
  • 
    

    4 hours after dose: 0.52 ± 0.09

  
  
  
  
• 
  

  Elevated in: gastrointestinal bacterial overgrowth, H ₂ blockers use

Bile, Urine

See Urine Bile

Bilirubin, Direct (Conjugated Bilirubin)

• 
  

  Normal range: 0 to 0.2 mg/dL

  
  
• 
  

  Elevated in: hepatocellular disease, biliary obstruction, drug-induced cholestasis, hereditary disorders (Dubin-Johnson syndrome, Rotor’s syndrome), advanced neoplastic states

Bilirubin, Indirect (Unconjugated Bilirubin)

• 
  

  Normal range: 0 to 1.0 mg/dL

  
  
• 
  

  Elevated in: hemolysis, liver disease (hepatitis, cirrhosis, neoplasm), hepatic congestion caused by congestive heart failure, hereditary disorders (Gilbert’s disease, Crigler-Najjar syndrome)

Bilirubin, Total

• 
  

  Normal range: 0 to 1 mg/dL

  
  
• 
  

  Elevated in: liver disease (hepatitis, cirrhosis, cholangitis, neoplasm, biliary obstruction, infectious mononucleosis), hereditary disorders (Gilbert’s disease, Dubin-Johnson syndrome), drug therapy (steroids, diphenylhydantoin, phenothiazines, penicillin, erythromycin, clindamycin, captopril, amphotericin B, sulfonamides, azathioprine, isoniazid, 5-aminosalicylic acid, allopurinol, methyldopa, indomethacin, halothane, oral contraceptives, procainamide, tolbutamide, labetalol), hemolysis, pulmonary embolism or infarct, hepatic congestion resulting from congestive heart failure Table 2.5 compares hereditary disorders of bilirubin metabolism and transport.

  
  
  
  

  TABLE 2.5

  
  

  Hereditary Disorders of Bilirubin Metabolism and Transport

  
  

  From Feldman M, Friedman LS, Brandt LJ: Sleisenger and Fordtran’s gastrointestinal and liver disease , ed 10, Philadelphia, Elsevier, 2016.

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Parameter	Gilbert’s	Type I Crigler-Najjar	Type II Crigler-Najjar	Dubin-Johnson	Rotor’s
  Incidence	6%–12%	Very rare	Uncommon	Uncommon	Rare
  Gene affected	UGT1A1	UGT1A1	UGT1A1	MRP2	OATP1B1 and OATP1B3
  Metabolic defect	↓Bilirubin conjugation	No bilirubin conjugation	↓↓Bilirubin conjugation	Impaired canalicular export of conjugated bilirubin	Impaired canalicular export of conjugated bilirubin
  Plasma bilirubin (mg/dL)	≤3 in absence of fasting or hemolysis, almost all unconjugated	Usually >20 (range, 17–50), all unconjugated	Usually <20 (range, 6–45), almost all unconjugated	Usually <7, about half conjugated	Usually <7, about half conjugated
  Liver histology	Usually normal, occasional →lipofuscin	Normal	Normal	Coarse pigment in centrilobular hepatocytes	Normal
  Other distinguishing features	↓Bilirubin concentration with phenobarbital	No response to phenobarbital	↓Bilirubin concentration with phenobarbital	→Bilirubin concentration with estrogens; →→urinary coproporphyrin I/III ratio	Mild →urinary coproporphyrin I/III ratio
  Prognosis	Normal (theoretical risk of selected drug toxicity)	Death in infancy if untreated	Usually normal	Normal (theoretical risk of selected drug toxicity)	Normal (theoretical risk of selected drug toxicity)
  Treatment	None	Phototherapy as a bridge to liver transplantation	Phenobarbital for →→bilirubin concentration	Avoid estrogens	None available

   
  

  MRP2, multidrug resistance–associated protein-2 gene; OATP, organic anion transporter; UGTIA1, bilirubin uridine diphosphate-glucuronyl transferase gene.
  
  

Bilirubin, Urine

See Urine Bile

Bladder Tumor–Associated Antigen

• 
  

  Normal: ≤14 U/mL. The test is used to detect bladder cancer recurrence. Sensitivity is 57% to 83% and specificity 68% to 72%.

  
  
• 
  

  Elevated in: bladder cancer, renal stones, nephritis, urinary tract infection, hematuria, renal cancer, cystitis, recent bladder or urinary tract trauma

Bleeding Time (Modified IVY Method)

• 
  

  Normal range: 2 to 9.5 minutes

  
  
• 
  

  Elevated in: thrombocytopenia, capillary wall abnormalities, platelet abnormalities (Bernard-Soulier disease, Glanzmann’s disease), drug therapy (aspirin, warfarin, antiinflammatory medications, streptokinase, urokinase, dextran, b-lactam antibiotics, moxalactam), disseminated intravascular coagulation, cirrhosis, uremia, myeloproliferative disorders, von Willebrand’s disease

  
  
• 
  

  Comments: The bleeding time test as a method to evaluate suspected hemostatic incompetence has been replaced in many laboratories with the platelet function analysis–100 assay. The bleeding time test’s ability to predict excessive bleeding in clinical situations such as surgery or invasive diagnostic procedures is poor. It may play a limited residual role in the evaluation of suspected hereditary disorders of hemostasis.

Blood Volume, Total

• 
  

  Normal: 60 to 80 mL/kg

  
  
• 
  

  Elevated in: polycythemia vera, pulmonary disease, congestive heart failure, renal insufficiency, pregnancy, acidosis, thyrotoxicosis

  
  
• 
  

  Decreased in: anemia, hemorrhage, vomiting, diarrhea, dehydration, burns, starvation

Bordetella pertussis Serology

• 
  

  Test description: Polymerase chain reaction of nasopharyngeal aspirates or secretions is used to identify Bordetella pertussis, the organism responsible for whooping cough.

BRCA-1, BRCA-2

• 
  

  This test involves the detection of carriers of mutations in the gene that are characterized by predisposition to breast and ovarian cancers. Women found to carry the mutation should undergo earlier and more intensive surveillance for breast cancer. Pretest counseling should be provided before genetic testing.

Breath Hydrogen Test

• 
  

  Normal: This test is for bacterial overgrowth. Fasting H ₂ excretion is 4.6 ± 5.1, after lactulose challenge, with an early increase of less than 12. Lactulose usually results in a colonic response more than 30 minutes after ingestion.

  
  
• 
  

  Elevated in: A high fasting breath H ₂ level and an increase of at least 12 ppm within 30 minutes after lactulose challenge are indicative of bacterial overgrowth in the small intestine. The increase must precede the colonic response.

  
  
• 
  

  False positives in: accelerated gastric emptying, laxative use

  
  
• 
  

  False negatives in: use of antibiotics and patients who are nonhydrogen producers

B-Type Natriuretic Peptide (BNP)

• 
  

  Normal range: up to 100 mg/L. Natriuretic peptides are secreted to regulate fluid volume, blood pressure, and electrolyte balance. They have activity in both the central and peripheral nervous system. In humans the main source of circulatory BNP is the heart ventricles.

  
  
• 
  

  Elevated in: heart failure. This test is useful in the emergency department setting to differentiate heart failure patients from those with chronic obstructive pulmonary disease presenting with dyspnea. Levels are also increased in asymptomatic left ventricular dysfunction, arterial and pulmonary hypertension, cardiac hypertrophy, valvular heart disease, arrhythmia, and acute coronary syndrome.

BUN

See Urea Nitrogen

C3

See Complement (C3, C4)

C4

See Complement (C3, C4)

CA 15-3

See Cancer Antigen 15-3

CA 27-29

See Cancer Antigen 27-29

CA 72-4

See Cancer Antigen 72-4

CA 125

See Cancer Antigen 125

Calcitonin (Serum)

• 
  

  Normal: <100 pg/mL

  
  
• 
  

  Elevated in: medullary carcinoma of the thyroid (particularly if level >1500 pg/mL), carcinoma of the breast, apudomas, carcinoids, renal failure, thyroiditis

Calcium (Serum)

• 
  

  Normal range: 8.8-10.3 mg/dL

  
  
• 
  

  Elevated in:

• 1.
  

  Malignancy: increased bone resorption via osteoclast-activating factors, secretion of pituitary hormone (PTH)–like substances, prostaglandin E ₂ , direct erosion by tumor cells, transforming growth factors, colony-stimulating activity. Hypercalcemia is common in the following neoplasms:

  
  
  
  
  • a.
    

    Solid tumors: breast, lung, pancreas, kidneys, ovary

    
    
  • b.
    

    Hematologic cancers: myeloma, lymphosarcoma, adult T-cell lymphoma, Burkitt’s lymphoma

  
  
  
  
• 2.
  

  Hyperparathyroidism: increased bone resorption, gastrointestinal (GI) absorption, and renal absorption. Hyperparathyroidism can be caused by the following conditions:

  
  
  
  
  • a.
    

    Parathyroid hyperplasia, adenoma

    
    
  • b.
    

    Hyperparathyroidism or renal failure with secondary hyperparathyroidism

  
  
  
  
• 3.
  

  Granulomatous disorders: increased GI absorption (e.g., sarcoidosis)

  
  
• 4.
  

  Paget’s disease: increased bone resorption, seen only during periods of immobilization

  
  
• 5.
  

  Vitamin D intoxication, milk-alkali syndrome, increased GI absorption

  
  
• 6.
  

  Thiazides: increased renal absorption

  
  
• 7.
  

  Other causes: familial hypocalciuric hypercalcemia, thyrotoxicosis, adrenal insufficiency, prolonged immobilization, vitamin A intoxication, recovery from acute renal failure, lithium administration, pheochromocytoma, disseminated systemic lupus erythematosus

  
  
• 
  

  Decreased in:

• 1.
  

  Renal insufficiency: hypocalcemia caused by the following:

  
  
  
  
  • a.
    

    Increased calcium deposits in bone and soft tissue secondary to increased serum PO ₄ ⁻³ level

    
    
  • b.
    

    Decreased production of 1,25-dihydroxyvitamin D

    
    
  • c.
    

    Excessive loss of 25-OHD (nephrotic syndrome)

  
  
  
  
• 2.
  

  Hypoalbuminemia: Each decrease in serum albumin (g/L) will decrease serum calcium by 0.8 mg/dL but will not change free (ionized) calcium

  
  
• 3.
  

  Vitamin D deficiency

  
  
  
  
  • a.
    

    Malabsorption (most common cause)

    
    
  • b.
    

    Inadequate intake

    
    
  • c.
    

    Decreased production of 1,25-dihydroxyvitamin D (vitamin D–dependent rickets, renal failure)

    
    
  • d.
    

    Decreased production of 25-OHD (parenchymal liver disease)

    
    
  • e.
    

    Accelerated 25-OHD catabolism (phenytoin, phenobarbital)

    
    
  • f.
    

    End organ resistance to 1,25-dihydroxyvitamin D

  
  
  
  
• 4.
  

  Hypomagnesemia: hypocalcemia caused by the following:

  
  
  
  
  • a.
    

    Decreased PTH secretion

    
    
  • b.
    

    Inhibition of PTH effect on bone

  
  
  
  
• 5.
  

  Pancreatitis, hyperphosphatemia, osteoblastic metastases: Hypocalcemia is secondary to increased calcium deposits (bone, abdomen).

  
  
• 6.
  

  Pseudohypoparathyroidism: autosomal recessive disorder characterized by short stature, shortening of metacarpal bones, obesity, and mental retardation. Hypocalcemia is secondary to congenital end organ resistance to PTH.

  
  
• 7.
  

  Idiopathic hypoparathyroidism, surgical removal of parathyroids (e.g., neck surgery)

  
  
• 8.
  

  “Hungry bones syndrome”: rapid transfer of calcium from plasma into bones after removal of a parathyroid tumor

  
  
• 9.
  

  Sepsis

  
  
• 10.
  

  Massive blood transfusion (as a result of EDTA in blood)

Table 2.6 summarizes a differential diagnosis of hypocalcemia based on laboratory evaluation.

Calcium, Urine

See Urine Calcium

Cancer Antigen 15-3 (CA 15-3)

• 
  

  Normal: <30 U/mL

  
  
• 
  

  Elevated in: approximately 80% of women with metastatic breast cancer. Clinical sensitivity is 0.60, specificity 0.87, positive predictive value 0.91. This test is generally used to predict recurrence of breast cancer and to evaluate response to therapy. May also be elevated in liver cancer, pancreatic cancer, ovarian cancer, and colorectal cancer. Elevations can also occur with benign breast and liver disease.

Cancer Antigen 27-29 (CA 27-29)

• 
  

  Normal: <38 U/mL

  
  
• 
  

  Elevated in: approximately 75% of women with metastatic breast cancer. Clinical sensitivity is 0.57, specificity 0.97, positive predictive value 0.83, negative predictive value 0.92. This test is generally used to predict recurrence of breast cancer and to evaluate response to therapy. May also be elevated in liver cancer, pancreatic cancer, ovarian cancer, and colorectal cancer. Elevations can also occur with benign breast and liver disease.

Cancer Antigen 72-4 (CA 72-4)

• 
  

  Normal: <4.0 ng/mL

  
  
• 
  

  Elevated in: gastric cancer (elevated in >50% of patients). Often used in combination with CA 19-9 and carcinoembryonic antigen to monitor gastric cancer after treatment.

Cancer Antigen 125 (CA-125)

• 
  

  Normal range: <35 U/mL

  
  
• 
  

  Elevated in: epithelial ovarian cancer; carcinoma of fallopian tube and endometrium; nonovarian abdominal malignancies; all forms of liver disease, especially those with cirrhotic ascites

Captopril Stimulation Test

• 
  

  Normal: This test is performed by giving 25 mg captopril orally after overnight fast. The patient should be seated during the test. After captopril administration, aldosterone is less than 15 ng/dL, renin greater than 2 ng Al/mL/hr.

  
  
• 
  

  Interpretation: In patients with primary aldosteronism, plasma aldosterone remains high and plasma renin activity remains low after captopril administration.

Carbamazepine (Tegretol)

• 
  

  Normal therapeutic range: 4 to 12 mcg/mL

Carbohydrate Antigen 19-9

• 
  

  Normal: <37.0 U/mL

  
  
• 
  

  Elevated in: gastrointestinal cancer, most commonly pancreatic cancer. The amount of elevation has no relation to tumor mass. Elevations can also occur with cirrhosis, cholangitis, and chronic or acute pancreatitis.

Carbon Dioxide, Partial Pressure

• 
  

  Normal range:

  
  
  
  
  • 
    

    Male: 35 to 48 mm Hg

    
    
  • 
    

    Female: 32 to 45 mm Hg

  
  
  
  
• 
  

  Elevated in: respiratory acidosis

  
  
• 
  

  Decreased in: respiratory alkalosis

Carbon Monoxide

See Carboxyhemoglobin

Carboxyhemoglobin (COHb)

• 
  

  Normal: saturation of hemoglobin <2%; smokers <9% (coma: 50%; death: 80%)

  
  
• 
  

  Elevated in: smoking, exposure to smoking, exposure to automobile exhaust fumes, malfunctioning gas-burning appliances

Fig. 2.3 illustrates the effects of oxygen on the dissociation of CO from carboxyhemoglobin.

The effects of oxygen on the dissociation of CO from carboxyhemoglobin (COHb). Oxygen breathing at 1 atm decreases the half-life of COHb to 60 minutes from approximately 300 minutes in air. Hyperbaric oxygen at 2.5 atm reduces the half-life to 30 minutes, allowing most of the COHb to be removed from the body within 90 minutes. Ata, atmosphere absolute.

From Auerbach P: Field guide to wilderness medicine, ed 4, St. Louis, Mosby, Elsevier, 2013.

Cardiac Markers (Serum)

Fig. 2.4 describes typical cardiac marker diagnostic window curves and serum levels after myocardial infarction.

Typical cardiac marker diagnostic window curves and serum levels after acute myocardial infarction (AMI).

From Lehmann CA: Saunders manual of clinical laboratory science, Philadelphia, WB Saunders, 1998.

Cardiac Troponins

See Troponins, Serum

Carcinoembryonic Antigen (CEA)

• 
  

  Normal range: nonsmokers: 0 to 2.5 ng/mL; smokers: 0 to 5 ng/mL

  
  
• 
  

  Elevated in: Colorectal carcinomas, pancreatic carcinomas, and metastatic disease usually produce higher elevations (>20 ng/mL); carcinomas of the esophagus, stomach, small intestine, liver, breast, ovary, lung, and thyroid usually produce lesser elevations; benign conditions (smoking, inflammatory bowel disease, hypothyroidism, cirrhosis, pancreatitis, infections) usually produce levels less than 10 ng/mL.

Cardio-CRP

See C-Reactive Protein

Carotene (Serum)

• 
  

  Normal range: 50 to 250 mcg/dL

  
  
• 
  

  Elevated in: carotenemia, chronic nephritis, diabetes mellitus, hypothyroidism, nephrotic syndrome, hyperlipidemia

  
  
• 
  

  Decreased in: fat malabsorption, steatorrhea, pancreatic insufficiency, lack of carotenoids in diet, high fever, liver disease

Catecholamines, Urine

See Urine Catecholamines

CBC

See Complete Blood Cell (CBC) Count

CCK

See Cholecystokinin-Pancreozymin

CCK-PZ

See Cholecystokinin-Pancreozymin

CD4 T-Lymphocyte Count (CD4 T-Cells)

• 
  

  Calculated as total white blood cells × % lymphocytes × % lymphocytes stained with CD4.

  
  
• 
  

  This test is used primarily to evaluate immune dysfunction in human immunodeficiency virus (HIV) infection and should be measured periodically in all HIV-infected persons. It is useful as a prognostic indicator and as a criterion for initiating prophylaxis for several opportunistic infections that are sequelae of HIV infection. Progressive depletion of CD4 T-lymphocytes is associated with an increased likelihood of clinical complications. Adolescents and adults with HIV are classified as having acquired immune deficiency syndrome (AIDS) if their CD4 lymphocyte count is less than 200/μL or if their CD4 T-lymphocyte percentage is less than 14%. Corticosteroids decrease CD4 T-cell percentage and absolute number.

CD40 Ligand

• 
  

  Normal: <5 mcg/L. CD40 ligand is a soluble protein that is shed from activated leukocytes and platelets and used in risk stratification for acute coronary syndrome.

  
  
• 
  

  Elevated in: acute coronary syndrome. Increased CD40 ligand is associated with higher incidence of death or nonfatal myocardial infarction.

CEA

See Carcinoembryonic Antigen

Cerebrospinal Fluid (CSF)

• 
  

  Normal range:

  
  
  
  
  • 
    

    Appearance: clear

    
    
  • 
    

    Glucose: 40 to 70 mg/dL

    
    
  • 
    

    Protein: 20 to 45 mg/dL

    
    
  • 
    

    Chloride: 116 to 122 mEq/L

    
    
  • 
    

    Pressure: 100 to 200 mm H ₂ O

  
  
  
  
• 
  

  Cell count (cells/mm ³ ) and cell type: <6 lymphocytes, no polymorphonucleocytes

  
  
• 
  

  Interpretation of results:

• 1.
  

  Appearance of the fluid:

  
  
  
  
  • a.
    

    Clear fluid indicates that results are normal.

    
    
  • b.
    

    Yellow (xanthochromia) in the supernatant of centrifuged CSF within 1 hour or less after collection is usually the result of previous bleeding (subarachnoid hemorrhage); it may also be caused by increased CSF protein, melanin from meningeal melanosarcomas, or carotenoids.

    
    
  • c.
    

    Pinkish color is usually the result of a bloody tap; the color generally clears progressively from tubes 1 to 4 (the supernatant is usually crystal clear in traumatic taps).

    
    
  • d.
    

    Turbidity usually indicates the presence of leukocytes (bleeding introduces approximately 1 WBC/500 red blood cells [RBCs] into the CSF).

  
  
  
  
• 2.
  

  CSF pressure: Elevated pressure can be seen with meningitis, meningoencephalitis, pseudotumor cerebri, mass lesions, and intracerebral bleeding.

  
  
• 3.
  

  Cell count: In adults the CSF is normally free of cells (although up to 5 mononuclear cells/mm ³ is considered normal); the presence of granulocytes is never normal.

  
  
  
  
  • a.
    

    Neutrophils: These are seen in bacterial meningitis, early viral meningoencephalitis, and early tuberculosis (TB) meningitis.

    
    
  • b.
    

    Increased lymphocytes are seen in TB meningitis, viral meningoencephalitis, syphilitic meningoencephalitis, and fungal meningitis.

  
  
  
  
• 4.
  

  Protein: Serum proteins are generally too large to cross the normal blood-CSF barrier; however, increased CSF protein is seen with meningeal inflammation, traumatic tap, increased CNS synthesis, tissue degeneration, obstruction to CSF circulation, and Guillain-Barré syndrome.

  
  
• 5.
  

  Glucose:

  
  
  
  
  • a.
    

    Decreased glucose is seen with bacterial meningitis, TB meningitis, fungal meningitis, subarachnoid hemorrhage, and some cases of viral meningitis.

    
    
  • b.
    

    A mild increase in CSF glucose can be seen in patients with very elevated serum glucose levels.

  
  

Table 2.7 summarizes characteristic cerebrospinal fluid abnormalities.

Ceruloplasmin (Serum)

• 
  

  Normal range: 20 to 35 mg/dL

  
  
• 
  

  Elevated in: pregnancy, estrogen therapy, oral contraceptive use, neoplastic diseases (leukemias, Hodgkin’s lymphoma, carcinomas), inflammatory states, systemic lupus erythematosus, primary biliary cirrhosis, rheumatoid arthritis

  
  
• 
  

  Decreased in: Wilson’s disease (values often <10 mg/dL), nephrotic syndrome, advanced liver disease, malabsorption, total parenteral nutrition, Menkes’ syndrome

Chlamydia Group Antibody Serologic Test

• 
  

  Test description: Acute and convalescent sera are drawn 2 to 4 weeks apart. A fourfold increase in titer between acute and convalescent sera is necessary for confirmation. A single titer 1:64 or higher is considered indicative of psittacosis or lymphogranuloma venereum.

Chlamydia Trachomatis Polymerase Chain Reaction (PCR)

• 
  

  Test description: performed on endocervical swab, urine, and intraurethral swab for detection of Chlamydia infection.

Chloride (Serum)

• 
  

  Normal range: 95 to 105 mEq/L

  
  
• 
  

  Elevated in: dehydration, sodium loss greater than chloride loss, respiratory alkalosis, excessive infusion of normal saline solution, cystic fibrosis, hyperparathyroidism, renal tubular disease, metabolic acidosis, prolonged diarrhea, acetazolamide administration, diabetes insipidus, ureterosigmoidostomy

  
  
• 
  

  Decreased in: vomiting, gastric suction, primary aldosteronism, congestive heart failure, syndrome of inappropriate antidiuretic hormone secretion, Addison’s disease, salt-losing nephritis, continuous infusion of D ₅ W, thiazide diuretic administration, diaphoresis, diarrhea, burns, diabetic ketoacidosis

Chloride (Sweat)

• 
  

  Normal range: 0 to 40 mmol/L

  
  
• 
  

  Borderline/indeterminate: 41 to 60 mmol/L

  
  
• 
  

  Consistent with cystic fibrosis: >60 mmol/L

  
  
• 
  

  False low results can occur with edema, excessive sweating, and hypoproteinemia.

Chloride, Urine

See Urine Chloride

Cholecystokinin-Pancreozymin (CCK, CCK-PZ)

• 
  

  Normal: <80 pg/mL

  
  
• 
  

  Elevated in: pancreatic disease, celiac disease, gastric ulcer, postgastrectomy state, irritable bowel syndrome, fatty food intolerance

Cholesterol, Low-Density Lipoprotein

See Low-Density Lipoprotein Cholesterol

Cholesterol, High-Density Lipoprotein

See High-Density Lipoprotein Cholesterol

Cholesterol, Total

• 
  

  Normal: generally <200 mg/dL

  
  
• 
  

  Elevated in: primary hypercholesterolemia, biliary obstruction, diabetes mellitus, nephrotic syndrome, hypothyroidism, primary biliary cirrhosis, diet high in cholesterol and total and saturated fat, third trimester of pregnancy, drug therapy (steroids, phenothiazines, oral contraceptives)

  
  
• 
  

  Decreased in: use of lipid-lowering agents (statins, niacin, ezetimibe, cholestyramine, colesevelam), starvation, malabsorption, abetalipoproteinemia, hyperthyroidism, hepatic failure, carcinoma, infection, inflammation

Chorionic Gonadotropin (hCG), Human (Serum)

• 
  

  Normal, serum:

  
  
  
  
  • 
    

    Male: <0.7 IU/L

    
    
  • 
    

    Female premenopausal: <0.8 IU/L

    
    
  • 
    

    Female postmenopausal: <3.3 IU/L

  
  
  
  
• 
  

  Elevated in: pregnancy, choriocarcinoma, gestational trophoblastic neoplasia (including molar gestations), placental site trophoblastic tumors. Human antimouse antibodies can produce false serum assay for hCG.

  
  
• 
  

  The principal use of this test is to diagnose pregnancy. In pregnancy, the concentration of hCG increases significantly during the initial 6 weeks of pregnancy. Peak values approaching 100,000 IU/L occur 60 to 70 days after implantation.

  
  
• 
  

  hCG levels generally double every 1 to 3 days. In patients with concentration less than 2000 IU/L, an increase of serum hCG less than 66% after 2 days is suggestive of spontaneous abortion or ruptured ectopic gestation.

Chymotrypsin

• 
  

  Normal: <10 mc/L

  
  
• 
  

  Elevated in: acute pancreatitis, chronic renal failure, oral enzyme preparations, gastric cancer, pancreatic cancer

  
  
• 
  

  Decreased in: chronic pancreatitis, late cystic fibrosis

Circulating Anticoagulant (Antiphospholipid Antibody, Lupus Anticoagulant)

• 
  

  Normal: negative

  
  
• 
  

  Detected in: systemic lupus erythematosus, drug-induced lupus, long-term phenothiazine therapy, multiple myeloma, ulcerative colitis, rheumatoid arthritis, postpartum, hemophilia, neoplasms, chronic inflammatory states, acquired immune deficiency syndrome, nephrotic syndrome

  
  
• 
  

  Note : The name is a misnomer because these patients are prone to hypercoagulability and thrombosis.

CK

See Creatine Kinase

Clonidine Suppression Test

• 
  

  Interpretation: Clonidine inhibits neurogenic catecholamine release and will cause a decrease in plasma norepinephrine into the reference interval in hypertensive subjects without pheochromocytoma. The test is performed by giving 4.3 mg clonidine/kg orally after overnight fast. Norepinephrine is measured at 3 hours. Result should be within established reference range and decrease to less than 50% of baseline concentration. Lack of decrease in norepinephrine is suggestive of pheochromocytoma.

Clostridium difficile Toxin Assay (Stool)

• 
  

  Normal: negative

  
  
• 
  

  Detected in: antibiotic-associated diarrhea ( Clostridium difficile infection [CDI]) and pseudomembranous colitis

CO

See Carboxyhemoglobin

Coagulation Factors

• 
  

  Factor reference ranges:

  
  
  
  
  • 
    

    V: >10%

    
    
  • 
    

    VII: >10%

    
    
  • 
    

    VIII: 50% to 170%

    
    
  • 
    

    IX: 60% to 136%

    
    
  • 
    

    X: >10%

    
    
  • 
    

    XI: 50% to 150%

    
    
  • 
    

    XII: >30%

  
  

Fig. 2.5 illustrates the blood coagulation pathways.

Simplified coagulation cascade. A , The coagulation cascade has historically been divided into two main pathways—the intrinsic and extrinsic pathways—both of which culminate in the formation of fibrin through the common pathway. It is now believed that factor IX activation by the factor VIIa/tissue factor (TF) complex plays a major role in the initiation of normal hemostasis. Once coagulation is activated, factor Xa binds to the tissue factor pathway inhibitor, which then effectively inhibits factor VIIa/TF. The factor VIIIa/IXa complex becomes the dominant generator of factor Xa and thus thrombin and fibrin formation. This model is consistent with the observation that deficiencies in factors VIII, IX, and, to a lesser extent, XI cause a bleeding diathesis, whereas the absence of factor XII, prekallikrein (PK), or high-molecular-weight kininogen (HMWK) does not. In the intrinsic pathway, factor XIIa activates prekallikrein into kallikrein. Kallikrein then activates more factor XIIa from factor XII. HMWK acts as a cofactor in both these reactions. HMWK also acts as a cofactor in the activation of factor XI by factor XII. Kallikrein releases bradykinin from HMWK, which has vasoactive activities. B , The activated partial thromboplastin time measures the clotting time from factor XII through fibrin formation. The prothrombin time (PT) measures the clotting time from factor VII through fibrin formation. TF is a transmembrane protein; thus, it is associated with phospholipid in vivo. Ca ²⁺ , calcium; PL, phospholipid, PTT, partial thromboplastin time.

From Henry JB, Davey FR, Herman CJ, et al, editors: Clinical diagnosis and management by laboratory methods , ed 20, Philadelphia, Saunders, 2001.

Cold Agglutinins Titer

• 
  

  Normal: <1:32

  
  
• 
  

  Elevated in: primary atypical pneumonia (Mycoplasma pneumonia), infectious mononucleosis, cytomegalovirus infection, others (hepatic cirrhosis, acquired hemolytic anemia, frostbite, multiple myeloma, lymphoma, malaria)

Complement (C3, C4)

• 
  

  Normal range: C3: 70 to 160 mg/dL; C4: 20 to 40 mg/dL

  
  
• 
  

  Abnormal values:

  
  
  
  
  • 
    

    Decreased C3: active systemic lupus erythematosus (SLE), immune complex disease, acute glomerulonephritis, inborn C3 deficiency, membranoproliferative glomerulonephritis, infective endocarditis, serum sickness, autoimmune or chronic active hepatitis

    
    
  • 
    

    Decreased C4: immune complex disease, active SLE, infective endocarditis, inborn C4 deficiency, hereditary angioedema, hypergammaglobulinemic states, cryoglobulinemic vasculitis