PB2028 PLATELET COUNTS WITHIN THE NORMAL RANGE UPON HOSPITALIZATION ARE PREDICTOR OF MORTALITY IN PATIENTS WITH COMMUNITY-ACQUIRED PNEUMONIA

Abstract

Background: Apart their role in haemostasis, platelets are immune cells and play a role in controlling infections. They have direct interaction with pathogens, like pneumococcus that activates platelets. Thrombocytopenia (<150 x 109/L) and thrombocytosis (>400 x 109/L) upon admission to hospital are predictors of mortality in community-acquired pneumonia patients. Because of a tight regulation of platelet count, we hypothesized that a slight increased platelet count in comparison with the mean (250 x 109/L), still within the normal range, also predicts mortality in these patients. Conversely, we hypothesized that a slight decreased platelet count, still within the normal range, reflects an appropriate involvement and consumption of activated platelets as immune system cells, and predicts a lower mortality. Aims: The objective of this study was to assess these hypotheses. Methods: The study included all adults in North and Central Denmark Regions with a first acute admission for community-acquired pneumonia during 2006-2012. Patients were identified within the Danish National Patient Registry using validated discharge diagnostic codes (J12-J18 of the International Classification of Diseases, version 10). We considered the first platelet count within +/- 24 hours of admission. We assessed the association between platelet count (within normal range: 150-400 x 109/L) and 30-day mortality using spline regression Cox models. Analyses were adjusted for age, sex, Charlson Comorbidity Index score, hemoglobin level, leukocyte count, and creatinine level upon admission. Sensitivity analysis was restricted to non-severe patients (not admitted to intensive care units within the first 48 hours following admission). Results: Among the 14 158 study patients, the 30-day mortality was 12.5%. Mean platelet count upon admission was 250 x 109/L. Compared with the mean, platelet counts between 175-250 x 109/L predicted up to 10% lower 30-day mortality, while platelet counts between 350-400 x 109/L predicted up to 20% higher 30-day mortality (Figure). A similar pattern was observed in non-severe patients.Summary/Conclusion: Platelet counts, even within the normal range, predict mortality in adults hospitalized for community-acquired pneumonia. A platelet count between 175-250 x 109/L may reflect an appropriate response of platelets against the pathogen.