The six-minute walk test as a measure of postoperative recovery after colorectal resection: further examination of its measurement properties

Introduction: Patients, clinicians and researchers seek an easy, reproducible and valid measure of postoperative recovery. The six-minute walk test (6MWT) is a low-cost measure of physical function, which is a relevant dimension of recovery. The aim of the present study was to contribute further evidence for the validity of the 6MWT as a measure of postoperative recovery after colorectal surgery. Methods: This study involved a sample of 174 patients enrolled in three previous randomized controlled trials. Construct validity was assessed by testing the hypotheses that the distance walked in 6 min (6MWD) at 4 weeks after surgery is greater (1) in younger versus older patients, (2) in patients with higher preoperative physical status versus lower, (3) after laparoscopic versus open surgery, (4) in patients without postoperative complications versus with postoperative complications; and that 6MWD (5) correlates cross-sectionally with self-reported physical activity as measured with a questionnaire (CHAMPS). Statistical analysis was performed using linear regression and Spearman’s correlation. The COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist was used to guide the formulation of hypotheses and reporting of results. Results: One hundred and fifty-one patients who completed the 6MWT at 4 weeks after surgery were included in the analysis. All hypotheses tested for construct validity were supported by the data. Older age, poorer physical status, open surgery and occurrence of postoperative complications were associated with clinically relevant reduction in 6MWD (>19 m). There was a moderate positive correlation between 6MWD and patient-reported physical activity (r = 0.46). Conclusions: This study contributes further evidence for the construct validity of the 6MWT as a measure of postoperative recovery after colorectal surgery. Results from this study support the use of the 6MWT as an outcome measure in studies evaluating interventions aimed to improve postoperative recovery.