False-negative result of serum cryptococcal antigen lateral flow assay in an HIV-infected patient with culture-proven cryptococcaemia

Abstract

The detection of cryptococcal capsular antigen (CrAg) is very sensitive and specific, however false-negative results have been reported, mostly in cerebrospinal fluid. We report the case of an HIV-infected patient with CD4 = 42 cells/mL, asthenic, negative serum CrAg lateral flow assay (LFA) and culture-proven cryptococcaemia. Despite the high accuracy of LFA, false-negative result is possible. Careful clinical evaluation and close follow-up are relevant. Keywords: Cryptococcosis, AIDS, Fungal antigens, False negative reaction, Prozone effect