in this study, although it may not have been immediately tis C in which there were no changes in albumin, bilirubin, or prothrombin time during deterioration of APC amongst apparent from studying the group data in Figs. 2 and3. The statement by Dr. Fabbri et al. that the variability between patients who had relapsed after a short-term response. We therefore continue to assert that monitoring of liver function these groups can be explained by differences in environmental factors is not an appropriate conclusion because we ex-using a sensitive test may be of value in charting the natural history of chronic hepatitis C. cluded patients from the study who were exposed to environmental factors, like drug ingestion, that would have a major GEOFFREY C. FARRELL, M.D., F.R.A.C.P. effect on APC. SHIRLEY A. COVERDALE, BScHons The disappointment expressed by Dr. Fabbri et al. will Storr Liver Unit continue to be felt if hepatologists believe that metabolic func-Department of Medicine tion tests have much value when used in transectional stud-University of Sydney at Westmead Hospital ies. That is not the point of the present studies in which Westmead, Australia serial tests were performed. We have previously shown that antipyrine clearance is more sensitive than tests such as the REFERENCE prothrombin time, serum albumin, and bilirubin concentra-1. Williams SF, Farrell GC. Serial antipyrine clearance studies detect altered tions in assessing serial hepatic function in chronic hepatitis hepatic metabolic function during spontaneous and interferon-induced changes in hepatitis B disease activity. HEPATOLOGY 1989;10:192-197.