Development and Validation of a Simplified Five-Variable Score for Predicting Massive Transfusion in Blunt-Trauma-Predominant Patients

Background/Objectives: Early identification of trauma patients requiring massive transfusion (MT) is essential for timely activation of massive transfusion protocols. Existing models have limitations: the Assessment of Blood Consumption (ABC) score includes penetrating injury, which limits its use where blunt trauma predominates; the Trauma-Associated Severe Hemorrhage (TASH) score requires numerous weighted variables; and the Traumatic Bleeding Severity Score (TBSS) requires blood pressure measured after crystalloid infusion. This study aimed to develop and validate a simplified MT prediction score using only variables available during initial assessment. Methods: We retrospectively analyzed 1462 adult trauma patients (366 MT, 1096 non-MT) treated at a regional trauma center in Korea between January 2020 and December 2025. Candidate predictors were identified by logistic regression, and five candidate models were compared. The final model, designated the Simplified Massive Transfusion (SMT) score, was compared with the ABC, TASH, and Modified TBSS scores in the same complete-case cohort using the area under the receiver operating characteristic curve (AUC) and the paired DeLong test. Results: The SMT score comprises five variables—systolic blood pressure ≤ 110 mmHg, lactate ≥ 4.0 mmol/L, ionized calcium ≤ 1.05 mmol/L, positive FAST, and pelvic fracture—each assigned one point (range, 0–5). In a common cohort of 1352 patients, the SMT score (AUC 0.846, 95% CI 0.822–0.870) performed similarly to the TASH score (0.841; p = 0.668) and significantly better than the Modified TBSS (0.821; p = 0.015) and the ABC score (0.783; p < 0.001). MT probability increased with increasing score, from 2.8% at a score of 0 to 82.9% at a score of 4. The observed rate at a score of 5 was 81.2%, but only 32 patients had this score. Conclusions: The SMT score, based on five readily available variables, showed discriminatory ability comparable to the TASH score and superior to the Modified TBSS and ABC scores. Since none of its components depends on the mechanism of injury, it may be broadly applicable across trauma populations. Further external validation in multicenter cohorts, especially those with a greater prevalence of penetrating trauma, is needed.