Objective: The objective of this study was to define the test characteristics of plasma beta-glucan for diagnosis of Pneumocystis jirovecii pneumonia (PCP) in AIDS patients with respiratory symptoms.
Design: Analysis of baseline blood samples in a randomized strategy study of patients with acute opportunistic infections, limited to participants with respiratory symptoms.
Methods: Participants in the 282-person ACTG A5164 trial had baseline plasma samples assayed for beta-glucan testing. As part of A5164 trial, two study investigators independently adjudicated the diagnosis of PCP. Respiratory symptoms were identified by investigators from a list of all signs and symptoms with an onset or resolution in the 21 days prior to or 14 days following study entry. Beta-glucan was defined as positive if at least 80 pg/ml and negative if less than 80 pg/ml.
Results: Of 252 study participants with a beta-glucan result, 159 had at least one respiratory symptom, 139 of whom had a diagnosis of PCP. The sensitivity of beta-glucan for PCP in participants with respiratory symptoms was 92.8% [95% confidence interval (CI) 87.2–96.5], and specificity 75.0% (95% CI 50.9–91.3). Among 134 individuals with positive beta-glucan and respiratory symptoms, 129 had PCP, for a positive predictive value of 96.3% (95% CI 91.5–98.8). Fifteen of 25 patients with a normal beta-glucan did not have PCP, for a negative predictive value of 60% (95% CI 38.7–78.9).
Conclusion: Elevated plasma beta-glucan has a high predictive value for diagnosis of PCP in AIDS patients with respiratory symptoms. We propose an algorithm for the use of beta-glucan as a diagnostic tool on the basis of the pretest probability of PCP in such patients.
aDivision of Infectious Diseases, Brigham and Women's Hospital and Harvard Medical School
bHarvard School of Public Health, Boston, Massachusetts
cDivision of Infectious Diseases and Department of Medicine, Stanford University School of Medicine, Stanford, California
dAssociates of Cape Cod, East Falmouth, Massachusetts, USA
eSchool of Medicine, University College Dublin, Dublin, Ireland
fDivision of Infectious Diseases and Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
*Current affiliation: Division of Allergy and Infectious Diseases, University of Washington, Seattle, Washington, USA.
Correspondence to Brian R. Wood, MD, Harborview Medical Center, 2W Clinic, 325 9th Avenue, Seattle, WA 98104, USA. Tel: +1 206 459 6410; fax: +1 206 744 5109; e-mail: firstname.lastname@example.org
Received 22 June, 2012
Revised 10 November, 2012
Accepted 16 November, 2012