Evaluation of bronchoalveolar lavage for differentiating between Pneumocystis jiroveci pneumonia and drug-induced pulmonary parenchymal disease after chemotherapy for solid tumors

Background: Differentiating between Pneumocystis jiroveci pneumonia (PCP) and drug-induced pulmonary parenchymal disease (DIPPD) is difficult after chemotherapy for solid tumors. The aim of this study was to evaluate the utility of bronchoalveolar lavage fluid (BALF) analysis for the diagnosis of PCP and DIPPD.Methods: We evaluated patients who underwent bronchoscopy at our institution from April 2012 to December 2014. Patients’ characteristics, comorbidity, previous treatment of solid tumor, and BALF findings were examined from the medical records.Results: From a total of 2625 consecutive patients who underwent bronchoscopy, 89 underwent BALF examination; among these, 33 cases had prior chemotherapy for malignancy. PCP was diagnosed in 6 patients and DIPPD was diagnosed in 21 patients. Six patients were diagnosed to have other pathologies or were undiagnosed. The white blood cell count in BALF (PCP (median (%) (range), DIPPD (median (%) (range)) consisted of macrophages (24.7 (6.9-46.1), 26.5 (2.1-86.0)), lymphocytes (71.3 (49.6-84.8), 57.0 (4.3-96.4)), neutrophils (4.6 (1.0-14.0), 5.0 (0.5-69.8)), and eosinophils (0.3 (0-1.3), 2.5 (0-37.0)). Only the proportion of eosinophils in the BALF of DIPPD patients was significantly higher (p = 0.016) than that of PCP patients. BAL was performed without serious complications.Conclusions: BALF differential count, especially eosinophils, may be useful in distinguishing between PCP and DIPPD to avoid unnecessary treatment. Further prospective studies would be needed to confirm this benefit of BAL.