Platelet Count within the Normal Range at Hospital Admission is Associated with Mortality in Patients with Community-Acquired Pneumonia

Background Apart from their hemostatic role, platelets are immune cells that play a role in fighting infections. The presence of thrombocytopenia and thrombocytosis at hospital admission are predictors of mortality in community-acquired pneumonia patients. We hypothesized that variations in platelet counts within the normal range also may be associated with mortality in these patients. Methods The study included all adults in the North and Central Denmark Regions with a first acute hospital admission for community-acquired pneumonia during 2006-2012. We assessed the association between the first platelet count within ± 24 hours of admission (within the normal range of 150 to 400 x 109/L) and 30-day mortality using Cox models. Analyses were adjusted for age, sex, Charlson Comorbidity Index score, hemoglobin level, leukocyte count, and creatinine level at admission. Results Among the 12,905 study patients, 30-day mortality was 12.4%. The mean platelet count upon admission was 250 × 109/L. Compared with the 250-275 × 109/L category, platelet counts of 151-175 were associated with a lower 30-day mortality (adjusted hazard ratio [aHR]: 0.79, 95% confidence interval [CI]: 0.63-0.99), while higher platelet counts were associated with a higher 30-day mortality (351-375 × 109/L, aHR: 1.34, 95% CI: 1.07-1.68; 376-400× 109/L, aHR: 1.21, 95% CI: 0.94-1.56). Conclusion Platelet counts, even within the normal range, are associated with mortality in adult patients hospitalized for community-acquired pneumonia.