Predictors and mortality in PCR-positive pneumocystis pneumonia among non-HIV patients

BACKGROUND: Pneumocystis jirovecii is a major cause of morbidity and mortality in HIV. It also poses a significant risk to non-HIV immunocompromised patients, especially those with cancer or recent chemotherapy. We evaluated risk factors, diagnostic markers-including lactate dehydrogenase (LDH)-and mortality predictors in PCR-confirmed pneumocystis pneumonia (PJP). METHODS: We retrospectively analyzed patients with hypoxemia, pulmonary involvement and/or fever who underwent PJP PCR testing at Koç University Hospital between January 2020 and November 2023. Cases were defined as patients with a positive PCR result who fulfilled the EORTC/MSGERC criteria for PJP, whereas the non-PJP group included PCR-negative patients and PCR-positive patients without clinically compatible disease. Clinical, laboratory, and radiologic data-including LDH, fungal load, co-infections, and 4-week mortality-were collected. RESULTS: Of 235 patients, 59 had PCR-confirmed PJP. PJP patients were older (median 70 vs. 64.5, p < 0.001), more often had solid organ malignancies (67.8% vs. 41.5%, p < 0.001), recent chemotherapy (66.1% vs. 41.5%, p = 0.001), and higher fungal loads (median 10,892 vs. 0, p < 0.001). Bilateral lung lesions (81% vs. 66.5%, p = 0.037) and ground-glass opacities (82.8% vs. 67.7%, p = 0.041) were more frequent. Serum LDH increased by 81.6% in PJP vs. 20.7% in controls (p = 0.001), whereas no significant difference was observed among patients with elevated baseline LDH (29.7% vs. 16.3%, p = 0.397). Multivariate analysis identified older age (OR 1.042, p = 0.017), solid organ malignancy (OR 2.304, p = 0.048), and CMV co-infection (OR 3.786, p = 0.006) as independent factors associated with PJP, whereas ICU admission at diagnosis was inversely associated with PJP (OR 0.239, p = 0.005). The 4-week mortality was 37%, with bacterial co-infection as the strongest predictor (OR 5.854, p = 0.009). CONCLUSION: Older age, solid organ malignancy, and CMV co-infection increased PJP risk, while bacterial co-infection predicted mortality. LDH changes supported diagnosis, but not when baseline levels were already elevated, in this predominantly oncology cohort.