Evaluation of (1 → 3)-β-D-glucan assay for diagnosing paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is highly prevalent in Latin America, but no commercial system is available for diagnosing this endemic mycosis.

To check the performance of (1 → 3)-β-D-glucan assay (BDG) for diagnosing  PCM in 29 patients with proven fungal disease and compared with double immunodiffusion assay for detecting anti-Paracoccidioides antibodies.

We selected 52 serum samples sequentially obtained from 29 patients with active PCM (12 chronic and 17 acute form). Samples were collected at baseline, and for 16 patients, additional serum levels were obtained after 3 and 6 months of antifungal treatment. Detection of BDG in serum was performed by using the Fungitell^® assay. For the double immunodiffusion assay, Paracoccidioides exoantigen was used in latex agglutination tests to detect serum anti-Paracoccidioides antibodies.

Despite exhibiting good sensitivity in the diagnosis of patients with PCM, we failed to demonstrate any correlation between the postdiagnosis kinetic profile of BDG serum levels and clinical response to antifungal therapy. This finding may be related to the maintenance of quiescent foci of fungal infection in several organs and tissues, a phenomenon that has been previously reported by other authors and helps to understand why so many relapses are documented in patients treated for short periods of time. Finally, we did not find any correlation between BDG quantification and specific anti-P brasiliensis antibodies serum titres in patients with PCM.

In conclusion, BDG is detected in serum samples of most patients with PCM but is probably not useful for predicting clinical response to antifungal therapy.