• Marwan M Azar, Rebecca Slotkin, Rita Abi-Raad, Yuehong Liu, Matthew H Grant, and Maricar F Malinis.
• From the Section of Infectious Diseases in the Department of Internal Medicine (Drs Azar, Grant, and Malinis), the Departments of Internal Medicine (Dr Slotkin), Pathology (Dr Abi-Raad), and Surgery (Dr Malinis), Yale University School of Medicine, New Haven, Connecticut; and School of Public Health (Ms Liu), Yale University, New Haven, Connecticut.
• Arch. Pathol. Lab. Med. 2020 Jan 6.

Context.—Direct visualization of Pneumocystis jiroveci organisms, using Gomori methenamine silver (GMS) staining in bronchoalveolar lavage fluid (BAL), is a historical gold standard that has been widely used for the diagnosis of P jiroveci pneumonia (PJP). However, the stain may be less sensitive in human immunodeficiency virus (HIV)-negative immunocompromised patients owing to a lower burden of organisms.Objectives.—To assess the sensitivity of the GMS stain on BAL fluid for the diagnosis of PJP in HIV-negative immunocompromised patients as compared to HIV-positive patients.Design.—We conducted a retrospective review from 2012 to 2018 to identify immunocompromised patients (≥18 years old) who underwent bronchoscopy with BAL GMS staining for the diagnosis of PJP. To assess for sensitivity, we sought to identify BAL GMS-positive cases and BAL GMS-negative cases of PJP. The BAL GMS-negative cases were categorized into proven and probable PJP.Results.—We identified 45 adult immunocompromised patients with proven and probable PJP, including 24 HIV-negative (11 BAL GMS-positive and 13 BAL GMS-negative) and 21 HIV-positive cases (all were BAL GMS-positive). The sensitivity of BAL GMS for the diagnosis of PJP in HIV-negative immunocompromised patients was 11 of 24 (46%) versus 21 of 21 (100%) in HIV-positive patients (CD4: median, 10 cells/mL; range, 3-300 cells/mL). Delayed or missed diagnoses were seen in 3 cases of BAL GMS-negative PJP. Re-examination of BAL GMS slides showed rare P jiroveci cysts in 1 case.Conclusions.—BAL GMS has poor sensitivity for PJP in HIV-negative immunocompromised patients. Using BAL GMS as a sole method for PJP may result in missed or delayed diagnoses in this population.

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