pulmonary disorders
Pneumocystis jirovecii Pneumonia
Diagnosis of Pneumocystis jirovecii Pneumonia
Chest x-ray Pulse oximetry Histopathologic confirmation To diagnosePneumocystis jiroveciipneumonia, patients should have chest x-ray and assessment of oxygenation by pulse oximetry. Chest x-raycharacteristically shows diffuse, bilateral perihilar infiltrates, but 20 to 30% of patients have normal x-rays. Hypoxemiamay be present even when chest x-ray shows no infiltrate; this finding can be an important clue to diagnosis. When pulse oximetry is abnormal, arterial blood gas (ABG) measurements are often obtained to show severity of hypoxemia (including an increase in the alveolar-arterial oxygen gradient). In immunosuppressed patients who have a dry, nonproductive cough and abnormal chest x-ray or pulse oximetry, pursue further testing forP. jiroveciipneumonia. If done, Overview of Tests of Pulmonary Function show altered diffusing capacity (although pulmonary function tests are rarely done as a diagnostic test for Serum beta-D glucan assays are nonspecific but can support the diagnosis. Histopathologic demonstrationofPneumocystis jiroveciiis needed for confirmation of the diagnosis.Methenaminesilver, Giemsa, Wright-Giemsa, modified Grocott, Weigert-Gram, or monoclonal antibody stain is used. Polymerase chain reaction (PCR)-based detection can add to the diagnostic yield. Sputum specimens are usually obtained by induced sputum or bronchoscopy. Sensitivity ranges from 30 to 80% for induced sputum and is>95% for bronchoscopy with bronchoalveolar lavage. 