Evaluation of a rapid lateral flow immunoassay for the detection of cryptococcal antigen for the early diagnosis of cryptococcosis in HIV patients in Colombia

Abstract

A previous study carried out in a tertiary care hospital in Colombia demonstrated the usefulness of the Cryptococcus capsular antigen detection by latex (CrAg Latex) in the early diagnosis of cryptococcosis in HIV-infected patients with low CD4 + levels. The aim of this study was to establish the performance of a new rapid lateral flow assay (CrAg LFA) in preserved sera of those HIV-infected patients collected between 2001 and 2006. A total of 421 sera from 297 patients with a confirmed diagnosis of HIV were tested with CrAg LFA and results compared with those obtained with CrAg Latex. All patients provided informed consent for specimen collection. A concordance of 100% was found between positive results obtained by both methods. However, 13 sera that were negative by CrAg Latex, were positive by CrAg LFA (3.1%). In these positive patients, median of CD4 + levels was 67 cells/μl (8-608 cells/μl), while median of viral load was 118,965 copies/ml (50-500,000 copies/ml). Patients who were negative for cryptococcosis had a median of 177 cells/μl in CD4 + levels (4-2516 cells/μl) and a median of 62,318 copies/ml in viral loads (25-50,000 copies/ml). A significant statistical difference was found when comparing CD4 + levels and viral load in patients positive for cryptococcosis and those that were proven to be negative (P < 0.0001). The use of Point-of-Care Tests (POCT) like CrAg LFA play an important role in the diagnosis of infectious diseases, especially in resource limited settings, where it will be a useful means to diagnose cryptococcosis early in HIV patients.