Validation of the SF-36 as a measure of postoperative recovery after colorectal surgery.

INTRODUCTION: Surgery is evolving, and new techniques are introduced to improve "recovery." Postoperative recovery is complex, and evaluating the effectiveness of surgical innovations requires assessment of patient-reported outcomes. The Short-Form-36 (SF-36), a generic health-related quality of life questionnaire, is the most commonly used instrument in this context. The objective of this study was to contribute evidence for the validity of the SF-36 as a metric of postoperative recovery.
METHODS: Data from 128 patients undergoing planned colorectal surgery at one university hospital between 2005 and 2010 were analyzed. In the absence of a gold standard, the responsiveness and construct validity (known groups and convergent) of the SF-36 were evaluated. Standardized response means were computed for the former and non-parametric tests were used to assess the statistical significance of the changes observed. Multiple linear regression was used to determine whether the SF-36 discriminates between patients with versus without complications and between laparoscopic and open surgery (known groups); correlations between the SF-36 and the 6-min walk test, a measure of functional walking capacity (convergent) was investigated with Spearman's rank correlation.
RESULTS: The SF-36 was sensitive to clinically important changes. Scores on six of eight domains and the physical component summary score deteriorated postoperatively (SRM 0.86 for the PCS, p < 0.01) and improved to baseline thereafter. Patients with complications had significantly lower scores on five SF-36 domains (with differences from -9 (-18, -1), p = 0.04 to -18 (-32, -2), p = 0.03), and scores on all subscales were lower than those in a healthy population (p < 0.01 to p = 0.04). The SF-36 did not differentiate between laparoscopic and open surgery. Physical functioning scores correlated with 6MWT distance at 1 and 2 months (Spearman's r = 0.31 and 0.36, p < 0.01).
CONCLUSIONS: The SF-36 is responsive to expected physiological changes in the postoperative period, demonstrates construct validity, and thus constitutes a valid measure of postoperative recovery after planned colorectal surgery. The SF-36 did not, however, discriminate between recovery after laparoscopic and open surgery.