The ABC score was derived in adult major trauma patients at a level I trauma centre to predict early need for massive transfusion, defined as transfusion of ≥10 units of packed red blood cells within 24 hours.

In a registry study of 596 highest-level trauma activations, 76 patients required massive transfusion; penetrating mechanism, systolic blood pressure ≤90 mmHg, heart rate ≥120 beats/min, and a positive FAST were the strongest independent predictors and were combined into the 0–4 point ABC score.

Using a threshold of ABC ≥2, the derivation study reported sensitivity around 75% and specificity around 86% for massive transfusion; subsequent external validations have found high negative predictive values (about 95–97%) and moderate positive predictive values (~50–55%), supporting the score’s use as a rule-in for massive transfusion protocol activation rather than as a stand‑alone transfusion decision tool.

American College of Surgeons trauma guidance and later reviews describe ABC score ≥2 as one acceptable trigger, alongside clinical judgement and other dynamic criteria, for activating institution-specific massive transfusion protocols.

Interpretation cautions

Use the result with bedside assessment, trajectory, comorbidity and local diagnostic or treatment pathways.
A low-risk value should not override clinical deterioration or clearly high-risk features.
Calibration may differ outside the derivation cohort, especially with newer tests, treatments or referral patterns.

The primary source provides the original method and supporting evidence.

ABC Score for Massive Transfusion