Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (745 page)

   Increased serum bilirubin with normal ALP suggests constitutional hyperbilirubinemias or hemolytic states.

   Due to renal excretion, maximum bilirubin is 10–35 mg/dL; if renal disease is present, it may reach 75 mg/dL.

   Conjugated bilirubin >1.0 mg/dL in an infant always indicates disease.

   Serum bilirubin (conjugated-to-total):

   Less than 20% conjugated: constitutional (e.g., Gilbert disease, Crigler-Najjar syndrome)

   Hemolytic states:

   Twenty to forty percent conjugated: favors hepatocellular disease rather than extrahepatic obstruction; disorders of bilirubin metabolism (e.g., Dubin-Johnson, Rotor syndromes)

   Forty to sixty percent conjugated: occurs in either hepatocellular or extra-hepatic type

   Greater than 50% conjugated: favors extrahepatic obstruction rather than hepatocellular disease

Suggested Readings

Dufour DR, Lott JA, Nolte FS, et al. Diagnosis and monitoring of hepatic injury. I. Performance characteristics of laboratory tests.
Clin Chem.
2000;46:2027–2049.

Stevenson DK, Wong RJ, Vreman HJ. Reduction in hospital readmission rates for hyperbilirubinemia is associated with use of transcutaneous bilirubin measurements.
Clin Chem.
2005;51:481–482.

BLEEDING TIME (BT)
*

   Definition

   BT is a functional test for primary hemostasis (platelets and small vessels), infrequently performed nowadays (see below under limitations).

   
Normal range:
4–7 minutes (slightly longer in women).

   Use