Associations of underlying diseases with inflammatory response and pulmonary imaging findings in adults with respiratory tract infections: a retrospective cohort study

The effect of comorbidity burden on inflammatory and imaging severity in respiratory tract infections remains unclear. We retrospectively analyzed 911 adults with respiratory tract infections and compared inflammatory markers and chest CT findings according to underlying diseases. Multivariable regression adjusted for age, sex, pathogen type and peak fever. False discovery rate (FDR) correction was applied for multiple comparisons. Patients with comorbidities were older and showed higher CRP, PCT, neutrophil count and NLR, with more frequent CT pneumonia but a lower proportion of bilateral lung infiltrates. Hypertension was independently associated with higher logCRP and logNLR, tumour history with higher logNLR(FDR-adjusted P = 0.035), and diabetes with lower logPCT. When patients were grouped by the number of underlying diseases (0, 1, ≥ 2), we observed statistically significant differences in logCRP levels and the incidence of CT findings, with a significant increase from 0 to 1 comorbidity, but no further increase between the 1 and ≥ 2 groups. Comorbidity burden may support early risk stratification in respiratory tract infections. Not applicable. This retrospective observational cohort study did not involve prospective assignment of participants to an intervention and therefore did not meet the definition of a clinical trial.