Sensitivity to change of health status measures in a randomized controlled trial: comparison of the COOP charts and the SF-36

Abstract

This study compared the sensitivity to change of comparable dimensions of a multi-item multi-dimensional health status measure (the SF-36) with the equivalent single item domains on the Dartmouth COOP charts. One hundred and twenty nine patients were randomized to either day case laparoscopic surgery (n = 60) or open inguinal hernia repair (n = 69). Respondents completed the SF-36 and COOP charts at baseline (prior to surgery) and at follow up at 10 days and 6 weeks. Equivalent dimensions of physical functioning, mental health/emotional condition, social activities, pain and overall condition/general health on the two questionnaires were compared. Despite slightly different pictures of change provided by the physical functioning and 'overall condition/general health' dimensions the general picture of change provided by the two instruments was similar. At 10 days, patients who underwent open surgery reported far greater levels of dysfunction than those who underwent laparoscopic surgery on both questionnaires. At 6 weeks the pain dimension of both questionnaires indicated a large improvement from baseline, whilst no other domain on either questionnaire for either group indicated such improvement. The general picture of change provided by the two measures was similar. The results suggest that both the SF-36 and the COOP charts may prove suitable for the assessment of health perception outcomes in surgical clinical trials. Differences on certain domains were caused in large measure by the nature of the questions posed. The study once again highlights the importance of checking item content to determine the suitability of any particular measure for a given study.