Association of Time-to-Treatment with Prognosis in Pneumocystis Pneumonia Among Immunocompromised Patients Without HIV Infection: A Multi-Center, Retrospective Observational Cohort Study

Background Pneumocystis jirovecii pneumonia (PCP) in non-human immunodeficiency virus (HIV) patients is associated with high morbidity and mortality. Although prior studies have linked delayed treatment to worse outcomes, they are often limited by small sample sizes and inadequate adjustment for confounders. Therefore, we evaluated whether early treatment after hospital admission improves mortality in non-HIV PCP, adjusting for patient characteristics. Methods This multi-center, retrospective, observational cohort study included non-HIV PCP patients treated between January 2006 and March 2021 at three institutions. Participants were divided into the early treatment (initiated within 2 days) and late treatment (initiated between days 3 and 7) groups. The primary endpoint was 30-day mortality, and the secondary endpoints were 180-day mortality. Propensity score weighting was used to adjust for patient background. Results Ninety-four patients in the early treatment group and 43 in the late treatment group were evaluated. The average time-to-treatment for the early and late treatment groups was 0.13 days and 3.63 days, respectively. After adjusting for patient characteristics, there were no significant differences in 30-day mortality (14.0% vs. 8.2%, p = 0.307) or 180-day mortality (21.5% vs. 17.7%, p = 0.095) between the early and late treatment groups. In a subgroup analysis of cases requiring oxygen supplementation, 30-day and 180-day mortality also showed no significant differences between the two groups. Conclusion This study emphasizes the importance of accurate diagnosis and tailored management based on disease severity rather than immediate empirical treatment, as early treatment initiation was not significantly associated with 30-day or 180-day mortality in non-HIV PCP.