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 10(9)/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 × 10(9)/L. Compared with the 250–275 × 10(9)/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 × 10(9)/L, aHR: 1.34, 95% CI: 1.07–1.68; 376–400× 10(9)/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.