Abstract / Summary
The hemoglobin-to-red cell distribution width ratio (HRR) is a readily available complete blood count–derived biomarker that reflects both oxygen-carrying capacity and systemic inflammation. Unlike biomarkers capturing the severity of the acute arrest event, HRR may reflect baseline physiological reserve. Although HRR has been associated with adverse outcomes in several critical illnesses, its prognostic value in out-of-hospital cardiac arrest (OHCA) patients after return of spontaneous circulation (ROSC) remains unclear. This study investigated the association between HRR measured after ROSC and short- and long-term mortality. This retrospective cohort study included adult non-traumatic OHCA patients who achieved ROSC at a tertiary center from 2010 to 2020. HRR was calculated from the first complete blood count obtained after ROSC and categorized into quartiles. The primary outcome was 3-year all-cause mortality. Secondary outcomes were mortality at 30 days, 1 year, and 5 years. Multivariable Cox proportional hazards models estimated adjusted hazard ratios (aHRs). Sensitivity analyses additionally adjusted for lactate and pH, and for clinically prespecified covariates. Receiver operating characteristic curves compared the discriminative performance of HRR with its individual components and other biomarkers. Among 735 patients, lower HRR was associated with older age, female sex, and greater comorbidity burden. Mortality decreased progressively across increasing HRR quartiles. For the primary outcome, 3-year mortality rates were 91.8%, 90.2%, 79.9%, and 68.9% from Q1 to Q4, and patients in Q4 had a lower risk of 3-year mortality than those in Q1 (aHR, 0.52; 95% CI, 0.39–0.70). Similar graded associations were observed for all secondary outcomes. These associations were generally preserved after additional adjustment for lactate and pH. HRR showed moderate discriminative performance across all time points, with areas under the curve that were significantly higher than those of the neutrophil-to-lymphocyte ratio but did not exceed those of its individual components. Lower HRR measured after ROSC was independently associated with higher short- and long-term mortality after OHCA, with the association persisting well beyond the acute post-arrest period. Rather than outperforming markers of acute arrest severity, HRR appears to capture a distinct, patient-related dimension of prognosis that may complement existing prognostic tools. Not applicable.