Should Serum Eosinophil Count Be Considered When Treating Pneumonia?

Aim: Eosinopenia is recognized as a potential indicator of infection, particularly in elderly patients and those requiring intensive care. While its established role in sepsis and various bacterial infections is documented, there are limited data on the impact of eosinophil levels in community-acquired pneumonia. This study aims to evaluate the association between low eosinophil counts and the predictive outcomes of pneumonia. Materials and Methods: Patients admitted with community-acquired pneumonia in our clinic between January and July 2023 were retrospectively evaluated. The demographic, clinical, and laboratory data, comorbidities, length of hospital stay, need for oxygen treatment, or non-invasive mechanical ventilation (NIV) support, and outcome of the infection were recorded. Additionally, complete blood count and biochemical test results were collected. Results: The study population comprised 116 patients (62 female and 54 male), with a mean age of 68.27±14.67 (21-91). Oxygen support was needed in 56 patients, while 21 cases required NIV; 21 patients were admitted to the intensive care unit (ICU), and 11 patients succumbedto the infection. Although no significant difference was found in eosinophil counts and percentages between patients requiring oxygen and those who did not, or between ICU admissions and discharges, a statistically significant difference was observed between patients who died and those who survived (P < 0.001). Notably, 91% of the deceased cases exhibited absolute eosinopenia (eosinophil count < 50/μL). Receiver operating characteristic (ROC) analysis indicated that eosinophil counts below 15/μL predicted mortality. Discussion: In our study, eosinopenia observed at hospital admission was identified as a significant marker of mortality in community-acquired pneumonia. Conclusion: Our findings suggest that eosinopenia, which is readily detectable in routine complete blood counts can serve as a valuable prognostic indicator in pneumonia cases.