Aspartate aminotransferase to platelet ratio index as a predictor of mortality in traumatic brain injury

Background: The Aspartate Aminotransferase-to-Platelet Ratio Index (APRI) is traditionally used to assess liver disease but may have prognostic value in other clinical contexts. This study evaluates APRI’s ability to predict mortality in traumatic brain injury (TBI) patients. Methods: This retrospective cohort study included 6252 adult TBI patients (Head/Neck Abbreviated Injury Scale (AIS) ≥3) from the Trauma Registry System at Kaohsiung Chang Gung Memorial Hospital, covering admissions from 1998 to 2023. APRI was calculated at admission using aspartate aminotransferase (AST) levels and platelet counts. The area under the receiver operating characteristic curve (AUC) was used to evaluate APRI’s predictive accuracy for mortality, and an optimal APRI cutoff was determined using Youden’s index. Patients were divided into high and low APRI groups based on this threshold, with mortality and other clinical outcomes compared. Results: Among the cohort, 5658 patients survived, and 594 patients died. APRI demonstrated moderate predictive accuracy for mortality, with an AUC of 0.648. The optimal cutoff for APRI was 0.59, yielding a sensitivity of 63.6% and specificity of 60.3%. Patients with APRI ≥0.59 had significantly higher mortality (14.5% vs. 5.9%, p < 0.001) and longer hospital stays (15.9 vs. 12.0 days, p < 0.001). After adjusting for confounders, elevated APRI remained independently associated with increased mortality (Adjusted odds ratio (AOR) = 1.67, 95% Confidence interval (CI): 1.37–2.02, p < 0.001). This association was strongest in patients with severe injury, indicated as Injury Severity Score (ISS) ≥25), where APRI ≥0.59 yielded an AOR of 1.74 (95% CI: 1.36–2.22, p < 0.001). Conclusions: These results indicate that an elevated APRI is a significant predictor of in-hospital mortality in moderate and severe TBI cases even after adjustment for confounders, whereas its prognostic value is minimal in patients with minor injuries. However, its predictive power remains limited, and APRI should be used alongside existing trauma scoring systems for comprehensive risk assessment, with prospective validation recommended. Prospective studies are recommended to validate APRI’s role in TBI and explore combined biomarker approaches to enhance predictive accuracy.