An Investigation of Mortality Associated With Comorbid Pneumonia and Thrombocytopenia in a Rural Southwest Missouri Hospital System.

Background: Pneumonia places a significant burden on individuals and society, contributing to a substantial number of hospital admissions, emergency department visits, deaths, and healthcare costs each year. Comorbidities can greatly increase the risk of poor outcomes when associated with pneumonia. One comorbidity that has yet to be thoroughly researched is thrombocytopenia, which is known to play an important role in activating the immune response to infections. A decrease in platelet count may limit the immune response and consequently increase mortality in patients with pneumonia. The purpose of this study was to investigate whether comorbid thrombocytopenia and pneumonia are associated with poor outcomes.

Methods: This study was a retrospective cohort analysis comparing mortality rates among patients with comorbid thrombocytopenia and pneumonia, pneumonia without thrombocytopenia, and thrombocytopenia without pneumonia. Data were collected from Freeman Health System using International Classification of Diseases, Tenth Revision (ICD-10) codes from January 1, 2019, to December 31, 2021. ICD-10 codes for pneumonia and thrombocytopenia were extracted and stratified into three groups: those with both pneumonia and thrombocytopenia, those with pneumonia without thrombocytopenia, and those with thrombocytopenia without pneumonia. Mortality rates were then compared across the three groups.

Results: There were 4,414 patients admitted with pneumonia and 1,157 admissions for thrombocytopenia without pneumonia. Among the 4,414 patients admitted with pneumonia, 3,902 did not have thrombocytopenia, while 512 had thrombocytopenia. Of the patients without thrombocytopenia, 14% (3,902) expired. Among the 512 patients with thrombocytopenia, 43% expired. In the thrombocytopenia without pneumonia group, 11% (1,157) expired.

Conclusion: These results indicate a significant increase in mortality in patients with both pneumonia and thrombocytopenia compared to those with pneumonia without thrombocytopenia (an increase in mortality of 28.93% with a 95% CI: 24.50-33.36%, P < 0.0001). While pneumonia itself increases mortality compared to the general population, patients with both pneumonia and thrombocytopenia exhibit even higher mortality rates.