Rapid diagnosis of cryptococcosis using an antigen detection immunochromatographic test

Current methods for cryptococcal antigen detection have some limitations. This study aimed at evaluating a lateral flow assay (LFA) for the diagnosis of cryptococcosis in a French University medical center.

A retrospective study was performed on samples collected from patients with a definitive diagnosis of cryptococcosis (group I 66 samples; 28 patients) or with non-Cryptococcus invasive fungal infection (group II 18 samples; 17 patients). In addition, 274 samples from 205 consecutive patients, either suspected of cryptococcal infection or routinely screened during their follow-up, were prospectively tested (group III). Cryptococcal antigen was assayed using LFA and an EIA. A latex-based test was used for confirmation.

Sensitivity calculated on group I and specificity on group II, were respectively at 100% and 90.0%. Two false positives were related to Trichosporon fungemia. Per-sample analysis on group III revealed sensitivity, specificity, positive and negative predictive values all at 100% for CSF, and at 100%, 98.9%, 75% and 100%, respectively for serum samples. LFA enabled the diagnosis of two cases of asymptomatic cryptococcosis.

The excellent diagnostic value and practicality (visual reading results in 15 min) of LFA make it fully appropriate for the diagnosis of cryptococcosis in this particular setting.