To Örebro University

Background: Soluble thrombomodulin, a marker of endothelial cell injury, is released into the circulation during endothelial damage and has been observed at elevated concentrations in bacterial infections. This study aimed to investigate the correlation of thrombomodulin concentrations in plasma and sputum with disease severity and etiology in bacterial community-acquired pneumonia (CAP).

Methods: A prospective study was conducted on adults hospitalized with radiologically confirmed bacterial CAP. Plasma and sputum samples were collected upon admission, and thrombomodulin concentrations were quantified using an enzyme-linked immunosorbent assay. The study included a multivariate analysis to assess whether thrombomodulin concentrations were associated with disease severity and/or bacterial etiology.

Results: Of 111 patients with bacterial CAP, including 15 with severe CAP (as defined by the American Thoracic Society/Infectious Diseases Society of America criteria) and 63 with pneumococcal etiology, thrombomodulin was measured in plasma in all patients and in sputum in 42 patients. Elevated plasma thrombomodulin concentrations were independently associated with severe CAP. Stratification by bacterial etiology showed that higher plasma thrombomodulin concentrations were linked to severe pneumonia only in patients with pneumococcal infection. The area under the receiver operating characteristic curve for detecting severe pneumococcal CAP was 0.87. Conversely, sputum thrombomodulin concentrations showed no association with disease severity or bacterial etiology.

Conclusions: Plasma thrombomodulin is a promising biomarker for identifying severe pneumococcal CAP. Sputum thrombomodulin did not correlate with disease severity or bacterial etiology. These findings support further investigation into the diagnostic and prognostic role of plasma thrombomodulin in bacterial infections.