Identifying optimal serum 1,3-β-D-Glucan cut-off for diagnosing Pneumocystis Jirovecii Pneumonia in non-HIV patients in the intensive care unit

Abstract Background Serum (1,3)-β-D-glucan (BDG) detection for diagnosis of Pneumocystis jirovecii pneumonia (PJP) in non-human immunodeficiency virus (HIV) immunocompromised patients lacks intensive care unit (ICU)-specific data. We aimed to assess its performance and determine the optimal cutoff for PJP in ICU population. Methods This retrospective study included critically ill non-HIV immunocompromised patients admitted to a medical ICU with suspected pneumonia, undergoing simultaneous microbiological testing for P. jirovecii on lower respiratory tract specimens and serum BDG. Confounders affecting BDG positivity were explored by multivariable logistic regression. Optimal cut-offs were derived from Youden’s index for the entire cohort and subgroups stratified by confounders. Diagnostic performance of serum BDG was estimated at different cutoffs. Results Of 400 patients included, 42% were diagnosed with PJP and 58.3% had positive serum BDG. Serum BDG’s area under the receiver operating characteristic curve was 0.90 (0.87–0.93). At manufacturer’s 150 pg/ml cut-off, serum BDG had high sensitivity and negative predictive value (94%), but low specificity and positive predictive value (67%). Confounders associated with a positive serum BDG in PJP diagnosis included IVIG infusion within 3 days (odds ratio [OR] 9.24; 95% confidence interval [CI] 4.09–20.88, p