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

(See the editorial commentary by Morris and Masur, on pages 203–204.) Background. Improved noninvasive diagnostic tests for Pneumocystis jirovecii pneumonia (PCP) are needed. We evaluated the test characteristics of plasma (1→3)-β-D-glucan (β-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 β-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 β-glucan result that could be analyzed, 173 (69%) of whom had received a diagnosis of PCP. Median β-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 β-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)-β-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.