C-reactive protein to albumin ratio shows non-linear association with stroke-associated pneumonia risk

This retrospective cohort study analyzed 1,595 consecutive patients admitted with acute ischemic stroke between September 2016 and September 2022. The study investigated the C-reactive protein to albumin ratio (CAR) as a predictor for stroke-associated pneumonia (SAP), which occurred in 376 patients (23.6% of the cohort). The primary analysis revealed a strong association between log2-transformed CAR and SAP risk, with patients in the highest CAR quartile having an odds ratio of 6.11 (95% CI: 3.63–10.27, p < 0.05).

A key finding was the identification of a non-linear threshold effect at CAR ≈ 0.14. Below this threshold, the association with SAP was modest (OR = 1.22, 95% CI: 1.02–1.45). Above this threshold, the risk increased substantially (OR = 2.03, 95% CI: 1.70–2.42). The threshold-based predictive model statistically outperformed a simple linear model (p < 0.05).

Safety and tolerability data for the biomarker measurement were not reported. The authors explicitly note that the study establishes association only, not causation. A key limitation is that non-linear relationships and threshold effects for CAR in SAP prediction remain unclear and require further investigation. Funding sources and potential conflicts of interest were not disclosed.

For clinical practice, this study provides preliminary evidence for a potential biomarker threshold that may help stratify pneumonia risk in stroke patients. However, given the retrospective, observational design and the acknowledged uncertainty around the threshold effect, CAR should not yet be used to guide clinical decisions. Prospective validation is needed to confirm these findings and establish clinical utility.