Evaluating the sensitivity of the Wako β-D-glucan assay for the diagnosis of candidemia caused by Candida parapsilosis

Candidemia poses diagnostic challenges because of non-specific symptoms and low sensitivity of blood cultures. The Wako (1,3)-β-D-glucan (BDG) assay was recently introduced in Europe; however, its diagnostic performance for Candida parapsilosis compared to that of the Fungitell assay, which has demonstrated lower sensitivity, remains unclear. We evaluated the diagnostic performance of Wako BDG and BDG levels in candidemia, focusing on C. parapsilosis. BDG samples obtained within ± 3 days of blood culture collection were retrospectively analyzed. Diagnostic performance was compared using multiple cutoffs, including manufacturer-recommended thresholds (Japan: 11 pg/mL, Europe: 7.0 pg/mL). BDG levels and clinical characteristics were compared between C. parapsilosis and non-parapsilosis Candida candidemia. We included 154 candidemia episodes (C. parapsilosis: n = 24, non-parapsilosis Candida: n = 130) and 3,856 control episodes. Using 11 pg/mL, sensitivity for C. parapsilosis was 38% (95% confidence interval [CI]: 21–57) versus 62% (95% CI: 54–70) for non-parapsilosis Candida (p = 0.041), with specificity 93%. Lowering the cutoff from 11 to 7.0 pg/mL increased the overall sensitivity from 58% (95% CI: 51–66) to 71% (95% CI: 63–77) while maintaining high specificity (90%) but did not eliminate the sensitivity gap for C. parapsilosis. The median BDG level was lower in C. parapsilosis (5.0 pg/mL, interquartile range [IQR]: 0–68) than in non-parapsilosis Candida (21 pg/mL, IQR: 7.2–97; p = 0.036). C. parapsilosis candidemia was most commonly catheter-related (67%), with 17% in-hospital mortality. Despite high specificity, Wako BDG assay showed significantly lower sensitivity and BDG levels for C. parapsilosis candidemia compared with non-parapsilosis Candida candidemia.