Risk adjustment for evaluating the outcome of urological operative procedures

Considerable public and media attention has been directed in recent years toward comparing performance at individual hospitals. So-called death league tables have been published in the media, ranking hospitals according to crude mortality rates. Crude rates of mortality and morbidity are clearly misleading. Therefore, scoring systems comparing treatment outcomes among physicians or hospitals on an objective basis are urgently required.

During a 12-month period we prospectively evaluated 651 patients at 2 urological units using a simple and well validated surgical scoring system. Patients had been admitted to the units for routine urological operations. The scoring system consists of a simple preoperative physiological score, a postoperative severity score and defined types of complications.

The morbidity and mortality rates for unit 1 were 7.4% and 1.3%, respectively. For unit 2 the morbidity and mortality rates were 14% and 8.8%, respectively. Despite the marked differences in these crude rates risk adjusted analysis revealed no significant difference (p <0.05). Receiver operating characteristics curve analysis likewise demonstrated no significant difference in mortality and morbidity for the 2 units.

Raw rates of mortality and morbidity are often inappropriately used to compare the performance of various surgical procedures, especially vascular and cardiothoracic surgery. In Great Britain at some institutions urological units are ranked according to mortality and morbidity outcome. As a consequence, important variables, such as patient physiological state at surgery and the type of procedure, are not considered. Our study shows that the scoring system applied is suitable for urological audit and may be a valuable tool for comparing performance at various units.