Leukocyte cell population data predict 30-day mortality in community-acquired pneumonia: A multicenter prospective study.

Early identification of patients with community-acquired pneumonia (CAP) at increased risk of death remains essential, but rapid and low-cost prognostic biomarkers are still needed. Cell population data (CPD), automatically generated during routine complete blood count (CBC) testing, reflect leukocyte morphology and functional activation. This study aimed to assess whether CPD parameters predict 30-day mortality in hospitalized patients with CAP. This multicenter, observational, prospective study included consecutive adults admitted with CAP to three teaching hospitals in northern Spain between November 2019 and November 2021. A Sysmex XN-20 analyzer was used to measure leukocyte CPD parameters at baseline and at Day 3-5. Prediction models for 30-day all-cause mortality were developed using baseline CPD values and, in the follow-up cohort, early changes in CPD values. A total of 1,782 patients were included, of whom 1,480 had Day 3-5 follow-up data; 98 patients died within 30 days. In the baseline cohort, coronavirus disease 2019 (COVID-19) status, male sex, age ≥65 years, neutrophil fluorescence distribution width (NE-WY) ≥617.4, and monocyte fluorescence intensity (MO-Y) ≥130 predicted 30-day mortality, with an area under the receiver operating characteristic curve (AUC) of 0.81 [95% confidence interval (CI): 0.76-0.85]. In the follow-up cohort, COVID-19 status, age ≥65 years, male sex, baseline neutrophil fluorescence intensity (NE-Y) ≥51.63, MO-Y ≥130, NE-Y increase ≥3.76, and MO-Y decrease ≤-12.49 predicted mortality, with an AUC of 0.82 (95% CI: 0.76-0.88). CPD-based leukocyte parameters may provide a rapid, accessible, and cost-effective tool for identifying hospitalized patients with CAP at increased risk of 30-day mortality.