The Role of Frequent Screening or Diagnostic Testing of Serum Cryptococcal Antigen in Liver Transplant Recipients: A Descriptive Epidemiology

Background Cryptococcosis is a notable infectious complication of liver transplantation. Currently, there is no recommendation for screening serum cryptococcal antigen (CrAg) levels in solid organ transplant recipients. We aimed to explore the role of serum CrAg in liver transplant recipients at an institution where posttransplant serum CrAg has been widely tested.Methods This retrospective study was conducted at a tertiary care center in Japan. All liver transplant recipients with serum CrAg measured either for screening or for diagnostic testing at least once after transplantation between April 2005 and March 2022 were included. For participants with either a positive CrAg test result or positive culture for Cryptococcus, we manually reviewed clinical manifestations, management, and prognosis from the medical records.Results During the study period, 12 885 serum CrAg tests (median, 16 tests per patient) were performed in 468 liver transplant recipients. The 1-year posttransplant incidence of positive serum CrAg test results and culture-proven cryptococcosis was 1.9% (9/468) and 0.6% (3/468), respectively. No patient with persistently negative serum CrAg test results showed growth of Cryptococcus in culture. Four patients had clinical manifestations consistent with cryptococcosis, of whom 2 (50.0%) started antifungal therapy promptly based on a positive serum CrAg test result. In contrast, 5 patients had no clinical manifestations. Three of the 5 (60.0%) patients did not receive antifungal therapy and remained free of clinical manifestations.Conclusions Serum CrAg test was more sensitive than culture among liver transplant recipients and prompted early diagnosis and antifungal therapy in symptomatic patients. However, serial screening of serum CrAg in asymptomatic patients may be of little value, with the potential for false-positive results. Serum cryptococcal antigen tests potentially prompt the diagnosis and antifungal therapy in liver transplant recipients with compatible clinical manifestations. However, frequent screening in all liver transplant recipients may be of little value given the low prevalence of cryptococcosis.