Longitudinal evaluation of the SF-36 quality of life questionnaire in patients with kidney stones

Although the 36-Item Short-Form General Health Survey (SF-36) has been utilized to assess quality of life (QoL) in cross-sectional studies, no longitudinal studies have evaluated this instrument in stone formers. Hence, we evaluated the performance of the SF-36 over time in a group of stone formers. From January to May 2007, the SF-36 was administered by independent interviewers to 155 patients with a history of stones, and 96 individuals subsequently completed a second questionnaire at a median interval of 18 months (10.3-28.5 months). Subjects were asked to report changes in stone status, interval procedures, and significant non-stone related changes. Changes in individual and composite scores of SF-36 were compared. Among the 96 patients who completed two SF-36 surveys, 75 patients denied experiencing a stone episode within the month preceding their initial or follow-up SF-36 form. No statistically significant differences in any of the SF-36 domains or the aggregate physical or mental health composite scores over time were noted in these patients. A total of 18 patients reported a stone event within the month preceding completion of the initial questionnaire but no stone event prior to the follow-up survey. No clinically or statistically significant changes in any of the SF-36 domains between the first and follow-up questionnaire were seen among these 18 patients. The results show the stability of the SF-36 over time in patients with no change in their stone status. However, the absence of significant changes in the SF-36 despite a change in stone status suggests that the SF-36 may not be an adequate tool to monitor quality of life over time in stone patients. Validated, disease-specific questionnaires are needed to facilitate comparison of treatment strategies for stone disease.