Evaluation of evidence-based pneumocystis jirovecii infection frequency and clinical outcomes in patients with hematologic malignancies

Objective: Pneumocystis jirovecii pneumonia (PJP) can be an important cause of mortality in patients with hematological malignancies, with risk being particularly increased by intensive chemotherapy, transplantation, and lack of prophylaxis. The aim of this study was to determine the frequency of PJP among patients with hematological malignancies presenting with pulmonary infections and to evaluate the clinical outcomes of PJP-positive cases. Materials and Methods: This study included 282 patients who were followed with a diagnosis of hematological malignancy and presented with infectious symptoms requiring bronchoalveolar lavage (BAL) between 2014 and 2022 at Demiroğlu Bilim University Istanbul Florence Nightingale Hospital. Only the first admission of each patient was included in the analysis. PJP was diagnosed based on clinical and radiological findings together with polymerase chain reaction (PCR) positivity in BAL samples. Demographic data, primary hematological diagnoses, transplantation status, comorbidities, laboratory parameters, use of prophylaxis, clinical outcomes of infection, concomitant infectious agents, and survival data were evaluated. Statistical analyses included descriptive methods, univariate and multivariate logistic regression, and Kaplan–Meier survival analysis. Results: Among 3,056 hematology patients followed between 2014 and 2022, the incidence of PJP was 1.3% (n=39). A total of 282 patients who underwent bronchoscopy with BAL sampling for suspected pulmonary infection were evaluated. Of these, 39 (13.9%) were positive for PJP by BAL-PCR and confirmed clinically and radiologically, and were treated accordingly. There was no significant difference in demographic characteristics between PJP (+) and PJP (–) groups. The overall mortality rate among PJP (+) patients was 20.5% (8/39). At presentation, CRP and LDH levels were significantly higher in PJP (+) patients compared to PJP (–) patients (p<0.05). In univariate analysis, the presence of Gram-negative bacteremia was significantly associated with mortality both in the overall cohort (p=0.037) and specifically in the PJP (+) group (p=0.008). In multivariate logistic regression analysis of the entire study population, advanced age (OR: 1.032; 95% CI: 1.00–1.06; p=0.038) and low albumin levels (OR: 0.244; 95% CI: 0.10–0.56; p<0.001) were identified as independent risk factors for post-infection mortality. In addition, PJP was observed not only in the early period after hematopoietic stem cell transplantation but also in later follow-up, and occurred even under prophylaxis. Conclusion: In our study, the incidence and mortality rates of PJP in both the overall population and in the subgroup of hematopoietic stem cell transplant recipients were consistent with current literature. Advanced age and hypoalbuminemia were identified as independent adverse prognostic factors for mortality. Despite current prophylactic strategies, PJP remains an important infectious complication in hematology patients, suggesting the existence of additional, as yet undefined, risk factors. Therefore, multicenter, large-scale, prospective studies are needed to provide stronger evidence.