Significant Mortality Reduction from Severe Pneumocystis jirovecii Pneumonia in People Living with HIV and Treated in the Intensive Care Unit, Croatia, 2002–2023

<i>Pneumocystis jirovecii</i> pneumonia (PCP) remains a frequent cause of intensive care unit (ICU) admission among people living with HIV (PLWH), despite widespread antiretroviral therapy (ART) use. We conducted a retrospective cohort study of 39 PLWH with PCP admitted to the ICU at the Croatian national HIV referral center between 2002 and 2023. Patients were grouped by calendar period (pre-2015 vs. post-2015, reflecting the adoption of the "test and treat" strategy in 2015). Primary outcomes included ICU, 30-day, and 1-year mortality. We also evaluated the association between in-ICU ART initiation and survival. There were 37 (94.9%) males with a median age of 49 years (Q1-Q3, 37.5-54.5). Thirty-three (84.6%) were newly diagnosed with HIV. There were no differences between the observed periods regarding demographic characteristics. ART was initiated in the ICU in 21 (53.8%) patients, more frequently after 2015 (<i>p</i> < 0.001). ICU, 30-day, and 1-year mortality rates were 53.9% (<i>n</i> = 21), 51.3% (<i>n</i> = 20), and 66.7% (<i>n</i> = 26), respectively. Survival significantly improved in the later period, with 1-year survival reaching 54.5% (12/22). In-ICU ART initiation was associated with improved survival in univariable analysis, but this effect attenuated after adjusting for APACHE II or calendar year. Early ART may offer benefit but remains confounded by disease severity and evolving care standards.