Evaluating the impact of medical treatment on the quality of life: a 5-year update.

A comparison of the studies investigating the impact of medical care on quality of life over a recent 5-year period (1980-1984) with those appearing during the preceding 5 years from 1975 to 1979 [1]reveals; that (a) 3 times as many (69 as compared to 23) appeared during the time span, that (b) almost two-thirds (60%) of the recent studies included a subjective measure of quality of life as compared to only 1 in 10 for the previous 5-year period, but that (c) one-shot, case studies designs still predominate. On the other hand, (d) the use of control groups doubled from 1981 to the present, although (c) the majority of studies continues to use samples of convenience (e.g. consecutive patients or treatment survivors) rather than employing random assignments or random sampling. Nevertheless, (f) the average size of samples has doubled from 90 to 178, and (g) whereas almost all of the studies in the earlier review concluded that the intervention being studied improved quality of life, now approx. 1 in 5 report negative outcomes with another 30% reporting mixed results. It is concluded that in spite of increasing methodological sophistication, investigation of the impact of medical care on quality of life will be hindered until there is better agreement as to what constitutes adequate assessment of the construct. Suggestions for how a consensus might be attained are discussed.