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## Introduction

TRISS determines the probability of survival (Ps) of a patient from the ISS and RTS using the following formulae:

Where 'b' is calculated from:

The coefficients b0 - b3 are derived from multiple regression analysis of the Major Trauma Outcome Study (MTOS) database. AgeIndex is 0 if the patient is below 54 years of age or 1 if 55 years and over. b0 to b3 are coefficients which are different for blunt and penetrating trauma. If the patient is less than 15, the blunt coefficients are used regardless of mechanism.

Blunt | Penetrating | |

b0 | -0.4499 | -2.5355 |

b1 | 0.8085 | 0.9934 |

b2 | -0.0835 | -0.0651 |

b3 | -1.7430 | -1.1360 |

## TRISS Calculator

The TRISS calculator determines the probability of survival from the ISS, RTS and patient's age. ISS and RTS scores can be inputted independently or calculated from their base parameters.

The TRISS Calculator will open as a

standalone window on your desktop.

## References

Boyd CR, Tolson MA, Copes WS: "Evaluating Trauma Care: The TRISS Method", J Trauma 27:370-378;1987

Trianalytics Inc: http://www.trianalytics.com