Platelet-based biomarkers: A new frontier in inflammation monitoring for respiratory infections

Background: Platelets play a crucial role in haemostasis and have emerging functions in inflammation, particularly in respiratory infections like pulmonary tuberculosis (PTB) and pneumonia. The objective of this study was to investigate alterations in platelet parameters and their relationship with erythrocyte sedimentation rate (ESR) in PTB and pneumonia patients, comparing them to healthy controls, to evaluate their diagnostic and prognostic potential. Methods: This retrospective case-control study was conducted at a tertiary care center, involving 450 participants: 158 PTB patients, 142 pneumonia patients, and 150 healthy controls. Laboratory data including platelet count, mean platelet volume (MPV), plateletcrit (PCT), platelet distribution width (PDW), and ESR were obtained from the hospital’s Laboratory Information System. Statistical analyses, including Receiver Operating Characteristic (ROC) curve analysis, were performed to determine the diagnostic efficacy of the tests. Results: PTB and pneumonia patients exhibited significantly higher platelet counts and PCT, along with lower MPV compared to controls (p<0.001). In PTB patients, platelet count showed a positive correlation with PCT and ESR, and a negative correlation with MPV and PDW (p<0.001). Similar patterns were noted in pneumonia patients. ROC curve analysis identified cutoff values for platelet count (312,500/μl) and PCT (0.21%), which showed moderate sensitivity and specificity for differentiating PTB from pneumonia. ESR with a cutoff of 66.5 mm/h demonstrated comparable diagnostic performance. Conclusions: Altered platelet counts and indices in PTB and pneumonia patients correlate significantly with ESR levels, suggesting their potential as non-invasive diagnostic and prognostic markers in respiratory infections.