Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (904 page)

   Serum 5′-nucleotidase (5′-N) and LAP parallel the increase in ALP in obstructive type of hepatobiliary disease, but the 5′-N is increased only in the latter and is normal in pregnancy and bone disease, whereas the LAP is increased in pregnancy but is usually normal in bone disease. GGT is normal in bone disease and pregnancy. Therefore, these enzymes are useful in determining the source of increased serum ALP. Although serum 5′-N usually parallels ALP in liver disease, it may not increase proportionately in individual patients.

   Bilirubin (“bile”) in urine implies increased serum conjugated bilirubin and excludes hemolysis as the cause. Often precedes clinical icterus. May occur without jaundice in anicteric or early hepatitis, early obstruction, or liver metastases. (Tablets detect 0.05–0.1 mg/dL; dipsticks are less sensitive; test is negative in normal persons.)

   Complete absence of urine urobilinogen strongly suggests complete bile duct obstruction; is normal in incomplete obstruction and decreased in some phases of hepatic jaundice. Increased in hemolytic jaundice and subsiding hepatitis. Increase may evidence hepatic damage even without clinical jaundice (e.g., some patients with cirrhosis, metastatic liver disease, congestive heart failure). Presence in viral hepatitis depends on the phase of disease (normal is <1 mg or 1 Ehrlich U/2-hour specimen).

ERYTHROCYTE SEDIMENTATION RATE (ESR)
*

   Definition

   ESR is the distance in millimeters that erythrocytes fall during 1 hour in a sample of venous blood (Westergren principle). Newer techniques allow the test to be performed in 30 minutes, resulting in improved turnaround time.

   
Normal range:
0–15 mm/hour in men and 0–20 mm/hour in women.

   Use

   ESR is not a good screening test because of its low sensitivity. CRP is superior to ESR because it is more sensitive and reflects a more rapid change in the patient’s condition. ESR may be used as a screening test to detect the presence of a systemic disease; however, a normal test does not exclude malignancy or other serious disease, although it does rule out temporal arteritis or polymyalgia rheumatica.

   Finding a much accelerated ESR (>100 mm/hour) in patients with ill-defined symptoms directs the physician to search for a severe systemic disease, especially paraproteinemias, disseminated malignancies, connective tissue diseases, and severe infections such as bacterial endocarditis.

   Finding a normal ESR in patients with paraproteinemia suggests the development of hyperviscosity syndrome.

   ESR is also used to monitor the course or response to therapy of diseases if greatly accelerated initially.