Diagnostic value of serum γ-glutamyl transferase and alkaline phosphatase activities in hepatobiliary disease in the cat

SUMMARY The diagnostic value of serum γ-glutamyl transferase (ggt) activity and serum alkaline phosphatase (alp) activity in the detection of liver disease in the cat (n = 69) was compared. On the basis of histologic examination of the liver, cats were assigned to 8 groups: group 1—complete extrahepatic bile duct obstruction (n = 5), group 2—cholangiohepatitis-cholangitis syndrome (n = 11), group 3—hepatic lipidosis (n = 15), group 4—neoplasia, including lymphosarcoma and myeloproliferative disease (n = 9), group 5—hepatic necrosis (n = 7), group 6—cirrhosis (n = 3), group 7—portosystemic vascular anomaly (n = 4), and group 8—miscellaneous (n = 15). Cats assigned to group 8 lacked substantial histologic abnormalities of the liver. The mean value ± sd of ggt in 20 clinically normal cats was 0.44 ± 0.26 IU/L. The highest ggt activity in clinical patients developed in groups 1, 2, and 6. The highest alp activity developed in groups 1 to 4. Significant correlations between ggt and alp activities were detected only in groups 2 (P < 0.001) and 5 (P < 0.10). Among 54 cats with hepatic disease, only 11% had both the ggt and alp activities within the normal ranges. Comparatively, 52% had alp activities within the normal range, and 17% had ggt activities within the normal range. The serum ggt activity had a better sensitivity, but lower specificity, than did the serum alp activity in the cat for the detection of hepatobiliary disease. In only one group (group 3) did the magnitudes of increased activity (number of times greater than normal) of serum alp commonly exceed that of serum ggt. On the basis of this study, it was recommended that ggt and alp activity are best used in combination for the detection of naturally developing liver disease because the combination gives the best sensitivity and negative predictive value, with no loss of positive predictive value.