Examination of cryptococcal glucuronoxylomannan antigen in bronchoalveolar lavage fluid for diagnosing pulmonary cryptococcosis in HIV-negative patients.

Abstract

We clarified the performance of a cryptococcal glucuronoxylomannan (GXM) antigen test using bronchoalveolar lavage fluid (BALF) samples, in an HIV-negative Japanese population. Between March 2008 and December 2014, we examined cryptococcal GXM antigens in both serum and BALF specimens from 429 cases at Nagasaki University hospital. The diagnoses, underlying diseases, chest computed tomography findings, and cryptococcal GXM antigen test results were retrospectively investigated. Twenty-three patients were confirmed to have pulmonary cryptococcosis, another six were clinically diagnosed with cryptococcosis because they were seropositive for the GXM antigen, and five possible cryptococcosis cases had BALF samples that were positive for the GXM antigen and serum samples that were negative. The test's sensitivities for detecting cryptococcal GXM antigens in serum and BALF samples, for confirmed cases, were 73.9% and 82.6%, respectively, and their respective specificities were 98.5% and 97.8%. Three of the five putative patients with cryptococcosis were treated with antifungal agents; the pulmonary lesions decreased in size in all treated patients. Both the BALF and serum GXM antigen titers showed positive correlations with the lesion sizes; however, the serum antigen titers showed a higher correlation (r = 0.490, P = .0033) than did the BALF titres (r = 0.312, P = .0724). The rate of GXM-positive BALF samples was higher than the rate for serum samples, especially for patients with pulmonary lesion diameters ≤25mm. Testing for the presence of the cryptococcal GXM antigen in BALF specimens might contribute to the early diagnosis of pulmonary cryptococcosis.