Use of Monitoring Gamma-Glutamyl Transpeptidase Levels After Liver Transplant: A Longitudinal Retrospective Analysis of a Single-Center's Experience.

OBJECTIVES Recently, gamma-glutamyl transpeptidase has garnered increased attention as a diagnostic tool in the early identification of liver disease. However, its value in liver transplant is largely unknown, as the disease processes leading to abnormal gamma-glutamyl transpeptidase levels and the expected temporal trends in gamma-glutamyl transpeptidase levels during the period after liver transplant remain unclear. MATERIALS AND METHODS Between January 2010 and August 2013, consecutive patients who underwent liver transplant at Vancouver General Hospital (Vancouver, Canada) were assessed longitudinally up to 1 year after liver transplant. A "gamma-glutamyl transpeptidase event" was defined as 2 abnormal gamma-glutamyl transpeptidase values (exceeding sex-specific limits of normal, at 55 U/L for female and 80 U/L for male patients) ≥ 1 week apart. RESULTS Our study included 147 liver transplant recipients. The median gamma-glutamyl transpeptidase level on day 1 after liver transplant was 73 U/L, which peaked to 435 U/L during the first month after liver transplant and returned to within normal parameters by 1 year. In total, there were 282 gamma-glutamyl transpeptidase events, with biliary complications (22%), acute rejection (16%), and hepatitis C virus recurrence (10%) being the most common causes. In 39% of events, no cause was identified. When attempting to identify a disease-associated event, if gamma-glutamyl transpeptidase was the initial liver biochemistry test to double in value, it had 42% sensitivity and 40% specificity. Comparatively, if gamma-glutamyl transpeptidase was the initial liver biochemistry test to become abnormal, it had 3% sensitivity and 93% specificity. CONCLUSIONS Although gamma-glutamyl transpeptidase almost universally becomes abnormal after liver transplant, a specific pathologic cause was not commonly identified. Interpreting the characteristics of gamma-glutamyl transpeptidase elevation has limited use for identifying the underlying reason for its elevation.