Blood (1→3)-β-D-Glucan as a Diagnostic Test for HIV-Related Pneumocystis jirovecii Pneumonia

Background. Improved noninvasive diagnostic tests for Pneumocystis jirovecii pneumonia (PCP) are needed. We evaluated the test characteristics of plasma (1 -> 3)-beta-D-glucan (beta-glucan) for HIV-related PCP among a large group of patients presenting with diverse opportunistic infections (OIs). Methods. The study population included all 282 participants in AIDS Clinical Trials Group A5164, a study of early versus deferred antiretroviral therapy in conjunction with initial therapy of acute OIs. Baseline plasma samples were assayed for beta-glucan, with standard assay reference values defining >= 80 pg/mL as positive. Before this analysis, diagnosis of PCP was independently adjudicated by 2 study investigators after reviewing reports from study sites. Results. A total of 252 persons had a beta-glucan result that could be analyzed, 173 (69%) of whom had received a diagnosis of PCP. Median beta-glucan with PCP was 408 pg/mL (interquartile range [IQR], 209-500 pg/mL), compared with 37 pg/mL (IQR, 31-235 pg/mL) without PCP (P < .001). The sensitivity of beta-glucan dichotomized at 80 pg/mL for the diagnosis of PCP was 92% (95% confidence interval [CI], 87%-96%), and the specificity was 65% (95% CI, 53%-75%); positive and negative predictive values were 85% (95% CI, 79%-90%) and 80% (95% CI, 68%-89%) respectively, based on the study prevalence of 69% of patients with PCP. Rates of abnormal lactate dehyrogenase levels did not differ significantly between those with and without PCP. Conclusions. Blood (1 -> 3)-beta-D-glucan is strongly correlated with HIV-related PCP. In some clinical centers, this may be a more sensitive test than the induced sputum examination and could reduce the need for both bronchoscopy and empirical therapy of PCP.