Incremental Prognostic Value of the C-Reactive Protein-to-Albumin Ratio Beyond a Parsimonious Clinical Reference Model in Critically Ill Patients with Acute Ischemic Stroke

Background and Objectives: The C-reactive protein-to-albumin ratio (CAR) is associated with mortality and poor outcome after acute ischemic stroke, but the association is not the same as added clinical usefulness. We evaluated whether admission CAR and follow-up CAR provide prognostic information beyond a prespecified parsimonious clinical reference model comprising age, neurological severity, and admission glucose in critically ill patients with acute ischemic stroke. Materials and Methods: In this single-center retrospective cohort of 146 adults with acute ischemic stroke managed in intensive care, CAR was calculated from C-reactive protein and serum albumin at emergency department admission and at the first intensive care laboratory assessment. The primary outcome was 90-day all-cause mortality. A clinical reference model (age, admission National Institutes of Health Stroke Scale [NIHSS] score, admission glucose) was compared with the same model augmented by log-transformed CAR using the area under the receiver operating characteristic curve (AUC), the DeLong test, likelihood-ratio (LR) testing, and bootstrap optimism-corrected performance. Results: Ninety-day mortality occurred in 32 of 146 patients (21.9%) (full cohort; primary complete-case analysis: 141 patients with 31 events). In the primary complete-case analysis (n = 141; 31 events), admission CAR was not independently associated with mortality (odds ratio per 1-SD log CAR 1.46, 95% confidence interval 0.91–2.33; p = 0.115). Adding admission CAR changed the AUC from 0.768 (0.676–0.860) to 0.783 (0.693–0.874) (ΔAUC +0.016, 95% confidence interval −0.024 to +0.055; DeLong p = 0.444; LR p = 0.113), with optimism-corrected point estimates of 0.750 and 0.754. Follow-up CAR did not add value (LR p = 0.159), and change in CAR did not improve discrimination (ΔAUC +0.001; LR p = 0.945); because intensive care sampling times were not standardized, these analyses assess incremental prognostic information rather than CAR kinetics. Admission CAR was not associated with poor 90-day functional outcome (odds ratio 1.09, 95% confidence interval 0.83–1.44; p = 0.530). Conclusions: Admission CAR did not demonstrate measurable incremental prognostic value beyond the prespecified clinical reference model, and follow-up CAR and change-based analyses did not improve prediction, although non-standardized sampling times mean that serial CAR kinetics were not fully evaluated. The confidence intervals remain compatible with both no effect and a positive effect of uncertain clinical relevance, but the observed improvement was insufficient to support CAR as a stand-alone or routinely additive prognostic marker in this setting.