Serum C-reactive protein-to-albumin ratio is a potential risk indicator for pneumonia: Findings from a prospective cohort study

Objective: Circulating C-reactive protein (CRP) and albumin are known biomarkers of systemic inflammation. C-reactive protein-to-albumin ratio (CAR), a novel biomarker, has been suggested to be a more reliable risk indicator for inflammatory conditions compared to CRP or albumin alone. Inflammatory processes underlie the pathophysiology of pneumonia, but the association between CAR and pneumonia has not been previously investigated. We aimed to assess the prospective association of CAR with pneumonia risk.
Methods: C-reactive protein and albumin were measured in serum samples at baseline from 2,489 men aged 42-61 years, from the Kuopio Ischemic Heart Disease study. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated from Cox regression analysis.
Results: During a median follow-up of 26.1 years, 598 cases of pneumonia were recorded. In analysis adjusted for age, body mass index, smoking status, history of type 2 diabetes, prevalent coronary heart disease, history of asthma, history of chronic bronchitis, history of tuberculosis, alcohol consumption, socioeconomic status, leisure-time physical activity, and total energy intake, the HR (95% CI) for pneumonia comparing top versus bottom thirds of CAR was 1.62 (1.31-2.00). The corresponding adjusted risk for serum CRP was 1.67 (1.34-2.07). There was no evidence of an association between serum albumin and pneumonia risk.
Conclusion: In middle-aged and older Finnish men, elevated serum CAR and CRP levels were each associated with an increased risk of pneumonia. Further research is needed to replicate these findings in other populations and assess the potential value of CAR in the prevention and management of pneumonia.