Data from 11,156 patients treated at the four Major Trauma Outcome Study controlled sites were used to estimate the effect on survival of each APACHE II preinjury illness condition (PIC). A case-control methodology was applied; 544 patients (4.8%) had one or more PICs. For each patient with a specific PIC we identified a set of matching patients with no PICs. A patient matches a PIC patient if both have the same mechanism of injury, the same coding of Revised Trauma Score variables (Glascow Coma Scale score, systolic blood pressure, respiratory rate), the same coded age per A Severity Characterization of Trauma) (ASCOT), and if they differ by no more than 0.5 for A, B, and C (the ASCOT components for serious injuries). The estimated survival probability for a PIC patient is either the survival rate for the patient's matched set or, if there are no matches, the patient's ASCOT survival probability. The survival probabilities were used to compare the actual and predicted numbers of survivors for each PIC, using z and W statistics. Computations of z and W were also made using ASCOT survival probabilities for each PIC patient. The results indicate profound effects of five PICs (hepatic, cardiovascular, respiratory, renal, diabetes) on trauma patient outcomes.
Conclusion: Pre-existing organ dysfunction has a profound effect on patient outcome even after controlling for age, anatomic and physiologic severity, and mechanism of injury. But, because of their relatively low incidence in this sample, PICs did not strongly influence institutional outcome performance as measured by z and W values.