Objective: To determine the usefulness of severity of illness measures in explaining the variation in costs observed in economic analyses of clinical trials.
Method: Hospital costs and three severity of illness measures (Medical Illness Severity Grouping System [MedisGroups], Acute Physiology and Chronic Health Evaluation [APACHE] II, APACHE III) were calculated for patients undergoing surgical management of gastrointestinal malignancies. Regression models were developed to determine the predictive ability of the severity of illness measures on total costs and length of stay of surgical patients.
Results: There was not a significant reduction in the cost variance among patients after correcting for severity with use of the MedisGroups score. APACHE II scores were a better predictor of total costs, although this relationship did not reach statistical significance. As a continuous variable, APACHE III scores explained $326 of extra cost for each point on the scale, and as a categorical variable, identified those patients who were most expensive to care for and with long lengths of stay.
Conclusion: Neither MedisGroups nor APACHE II were found to be useful in explaining cost variations in a clinical trial. The APACHE III system was more useful in discriminating resource intensive patients.