Diagnostic Performance of the (1→3)-β-D-Glucan Assay for Invasive Fungal Disease

Background. Diagnosis of invasive fungal disease (IFD) is challenging, and it remains a significant cause of morbidity and mortality in immunocompromised patients. The (1 -> 3)-beta-D-glucan (BG) assay may be a useful adjunct, but its diagnostic performance is not well characterized. Methods. We retrospectively assessed the diagnostic indices of the BG assay in patients at risk of IFD who had a compatible clinical syndrome for the diagnosis of IFD a week after initial BG testing and at the end of the hospitalization associated with the first BG value. Patients with IFD were classified according to current European Organization for Research and Treatment of Cancer-Mycoses Study Group criteria, independent of BG results. Results. A total of 1308 BG assays were performed for 871 patients. One hundred twelve proven or probable IFD cases were diagnosed within 1 week after initial testing, and 116 cases were diagnosed by the end of hospitalization. Sensitivity of an initial BG level >= 80 pg/mL for IFD at 1 week was 0.64 (95% confidence interval [CI], 0.55-0.73), specificity was 0.84 (95% CI, 0.81-0.86), the positive likelihood ratio was 3.93 (95% CI, 2.94-5.26), and the negative likelihood ratio was 0.43 (95% CI, 0.31-0.59). Albumin, intravenous immunoglobulin, and hemodialysis were associated with elevated BG levels in patients without IFD (odds ratio, 4.78; 95% CI, 2.59-8.80). After excluding patients with these factors, specificity and the positive likelihood ratio of an initial BG level >= 80 pg/mL increased slightly. Empirical systemic antifungal treatment did not reduce overall BG sensitivity. Sensitivity was slightly lower among patients with hematologic malignancy or stem cell transplantation. Consideration of BG results would have increased the diagnostic certainty to probable in 54% of possible IFD cases. Conclusions. BG level appears to be a fair diagnostic adjunct for IFD in patients with appropriate pretest probability and a suggestive clinical syndrome, especially when checked serially in patients not receiving factors associated with an elevated BG level in the absence of IFD.