THE HIT AND MISS OF ISS AND TRISS

Objective-To measure interobserver variation in recording injury from case notes and its effect on calculating injury severity scores (ISS) from identical data and predicting probabilities of survival by using the combined trauma and injury severity score (TRISS). Design-Observer variation study using injury severity scoring and subsequent calculat ion of probability of survival based on combined trauma and injury sev erity scores. Subjects-16 patients with a range of injury severity sco res, and 15 observers.Results-There was a wide variation in recorded i njury severity scores, the probability of two observers agreeing on th e score being 0.28 (28%). The probability of any two observers agreein g over which severity band the patient should be in was 0.5 (50%). Obs erver variation was independent of the training and type of observer. Survival probability (calculated by combined trauma and injury severit y scoring methodology from individual observers' scores) varied by ove r 0.2 in six of the 16 patients and by over 0.5 in three. Conclusions- There is wide observer variation in injury severity scoring, which hig hlights a potential fallibility in its use for trauma audit. The use o f combined trauma and injury severity scoring for individual predictio n of survival is potentially inaccurate except at the extremes of prob abilities. The use of the 0.5 survival fine on a combined trauma and i njury severity score ''pre-chart'' is statistically and clinically ina ppropriate.