Cryptococcal antigen lateral flow: does testing of lower respiratory tract specimens improve diagnostic accuracy for pulmonary cryptococcosis?

Standard-of-care serological testing for cryptococcosis includes cryptococcal antigen detection from serum and cerebrospinal fluid (FDA clearance). Diagnosis of pulmonary cryptococcosis remains challenging due to nonspecific clinical presentations and limited sensitivity of conventional testing methods. In a recent study by X. Chen, Z. Wang, C. Di, F. Zhang, et al. (Microbiol Spectr 14:e01083-25, 2026, https://doi.org/10.1128/spectrum.01083-25 ), the authors assessed the performance of cryptococcal antigen testing by immunochromatographic lateral flow assay (CrAg-LFA) on bronchoalveolar lavage fluid (BAL) from 514 patients suspected of having pulmonary cryptococcosis (42 confirmed). While BAL CrAg-LFA testing had high sensitivity (88.1%), similar to serum CrAg-LFA sensitivity (90.5%), combined BAL and serum testing increased the sensitivity to 100% with a 100% negative predictive value. The study suggested that BAL CrAg-LFA may provide added diagnostic value when serum CrAg-LFA is negative, but high suspicion for pulmonary cryptococcosis remains.