Clinical Medicine & Physiology
TRISS Trauma Survival Probability Formula: Blunt vs Penetrating RTS + ISS + Age Logit
Compute Carl R. Boyd et al.’s (1987, MTOS) Trauma and Injury Severity Score (TRISS) hospital survival probability P_s = 1 / (1 + EXP(-b)) combining physiological RTS, anatomical ISS, Age >= 55, and Blunt vs Penetrating trauma coefficients.
Unify physiology (RTS), anatomy (ISS), patient age, and mechanism into a single Trauma Survival Benchmark!
Formulated by Carl R. Boyd, Mary Ann Tolson, and Wayne S. Copes (1987, Journal of Trauma, Major Trauma Outcome Study MTOS), TRISS benchmarks trauma-center performance (W- and Z-statistics) by computing expected hospital survival probability P_s = 1 / (1 + EXP(-b)) from linear predictor b = b_0 + b_1 * RTS + b_2 * ISS + b_3 * Age_55!
Here RTS (0 to 7.8408) is Champion’s weighted Revised Trauma Score, ISS (1 to 75) is Baker’s anatomical Injury Severity Score, Age_55 = 1 if patient age >= 55 years (else 0), and classic MTOS coefficients distinguish Blunt Trauma (b_0 = -1.2470, b_1 = +0.9544, b_2 = -0.0768, b_3 = -1.9052) from Penetrating Trauma (b_0 = -0.6029, b_1 = +1.1430, b_2 = -0.1516, b_3 = -2.6676)!
| TRISS Parameter | Classic MTOS Blunt Coefficients | Classic MTOS Penetrating Coefficients |
|---|---|---|
| Intercept b_0 | -1.2470 | -0.6029 |
| Physiological Weight b_1 * RTS (0..7.8408) | +0.9544 * RTS | +1.1430 * RTS |
| Anatomical Weight b_2 * ISS (1..75) | -0.0768 * ISS | -0.1516 * ISS |
| Senior Reserve Penalty b_3 * I(Age >= 55) | -1.9052 (if Age >= 55) | -2.6676 (if Age >= 55) |
TRISS Log-Odds Linear Predictor b (Blunt vs Penetrating MTOS Coefficients)
Computes b from trauma mechanism B2 ("BLUNT" or "PENETRATING"), RTS B3 (0..7.8408), ISS B4 (1..75), and Age B5.
=IF(OR(AND(UPPER(TRIM(B2 & "")) <> "BLUNT", UPPER(TRIM(B2 & "")) <> "PENETRATING"), B3 < 0, B3 > 7.85, B4 < 1, B4 > 75, B5 < 0, B5 > 120), "Invalid TRISS Inputs", ROUND(IF(UPPER(TRIM(B2 & "")) = "BLUNT", -1.247 + 0.9544 * B3 - 0.0768 * B4 - 1.9052 * IF(B5 >= 55, 1, 0), -0.6029 + 1.143 * B3 - 0.1516 * B4 - 2.6676 * IF(B5 >= 55, 1, 0)), 4))TRISS Predicted Hospital Survival Probability P_s (%)
Evaluates ROUND(100 / (1 + EXP(-b)), 2).
=IF(OR(AND(UPPER(TRIM(B2 & "")) <> "BLUNT", UPPER(TRIM(B2 & "")) <> "PENETRATING"), B3 < 0, B3 > 7.85, B4 < 1, B4 > 75, B5 < 0, B5 > 120), "Invalid TRISS Inputs", ROUND(100 / (1 + EXP(-IF(UPPER(TRIM(B2 & "")) = "BLUNT", -1.247 + 0.9544 * B3 - 0.0768 * B4 - 1.9052 * IF(B5 >= 55, 1, 0), -0.6029 + 1.143 * B3 - 0.1516 * B4 - 2.6676 * IF(B5 >= 55, 1, 0)))), 2))Try the example
Use the original values or change them to test your understanding.