Measuring outcome of total knee replacement using quality of life indices.

A series of 26 patients was studied before and after total knee replacement to determine the change in their quality of life, expressed as a gain in Quality Adjusted Life Years (QALYs). Global health status was assessed using the Nottingham Health Profile, disability by the Harris scale, pain by the McGill Pain Questionnaire, and anxiety and depression by the Hospital Anxiety and Depression Scale. Substantial reductions were found in pain, anxiety and depression, and a significant improvement was found in mobility. These data were used to generate a 'QALY' (Quality Adjusted Life Year) comparable to the measure used by Williams (1) in his comparative evaluation of medical and surgical treatments. A gain of only 0.42 QALY was found for knee replacement, which is about one-tenth the figure given by Williams for hip replacement. The difference appears to be attributable not to differences in the success of the operations, but rather to the scope that QALY calculations give for allocating comparable patients to different quality of life states. Tighter criteria are needed if QALYs are to be used to guide resource allocation.