Lower beta-1,3-D-glucan testing cut-offs increase sensitivity for non-albicans Candida species bloodstream infections.

Abstract

Fungal biomarkers support early diagnosis of invasive fungal infections. In this study, we evaluated the impact of a recent update to the manufacturer-recommended cut-off for beta-1,3-D-glucan (BDG) testing (Fujifilm Wako BDG assay) on sensitivity and specificity for the detection of candidemia. Additionally, we compared the performance with tests for Candida antigen (Ag by Serion ELISA antigen Candida, Virion\Serion) and anti-mannan antibodies (Ab by Hemkit Candida IHA, Ravo Diagnostika). Sera of 82 patients with candidemia, which were sampled with a maximum distance of ±14days from the date of sampling of the corresponding positive blood cultures, were retrospectively analysed for BDG, Ag and Ab. Results of BDG testing were compared with results from sera of 129 patients with candidemia from a different hospital. Sensitivity of BDG testing (47%) was higher than for Ag (17%) or Ab (20%). By combining Ag and Ab testing, sensitivity was raised to 32%. Lowering the cut-off of BDG from 11pg/ml to the newly recommended cut-off of 7pg/ml resulted in a significant increase in sensitivity (47% vs 58%, p=.01 and 63% vs 71% p<.01). At both centres, the increase was significant in NAC but not in C.albicans candidemia. No significant effects on specificity were observed. BDG testing outperformed Ag and Ab testing and its combination. Lowering the BDG cut-off had no significant impact on specificity. The increase in sensitivity can be mainly attributed to a gain in sensitivity for non-albicans Candida species bloodstream infections.