Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (941 page)

   Obstructive jaundice. Increase is faster and greater than that of serum ALP and LAP; average increase more than five times ULN.

   Liver metastases; parallels ALP; elevation precedes positive liver scans. Average increase >14 times ULN.

   Cholestasis. In mechanical and viral cholestasis, GGT and LAP are increased about equally, but in drug-induced cholestasis, GGT is much more increased than LAP. Average increase more than six times ULN.

   Children; much more increased in biliary atresia than in neonatal hepatitis (300 IU/L is useful differentiating level). Children with α1-antitrypsin deficiency have higher levels than other patients with biliary atresia.

   Pancreatitis. The GGT level is always elevated in acute pancreatitis. In chronic pancreatitis, it is increased when there is involvement of the biliary tract or active inflammation.

   AMI; increased in 50% of patients. Elevation begins on the 4th to the 5th day, reaching a maximum at 8–12 days. With shock or acute right heart failure, an early peak may appear within 48 hours, with a rapid decline followed by a later rise.

   When increased, it is a risk factor for myocardial infarction and cardiac death.

   Heavy use of alcohol; the most sensitive indicator and a good screening test for alcoholism, because elevation exceeds that of other commonly assayed liver enzymes.

   Some cases of carcinoma of the prostate.

   Neoplasms, even in the absence of liver metastases; especially malignant melanoma, carcinoma of the breast and lung; highest levels seen in hypernephroma.

   Others (e.g., gross obesity [slight increase], renal disease, cardiac disease, postoperative state).

Decreased In

   Hypothyroidism

Normal In

   Pregnancy (in contrast to serum ALP, LAP) and children older than 3 months of age; therefore, may aid in differential diagnosis of hepatobiliary disease occurring during pregnancy and childhood