The 6-minute walk test in outpatient cardiac rehabilitation: validity, reliability and responsiveness--a systematic review.

BACKGROUND The 6-minute walk test (6MWT) is a common outcome measurement in cardiac rehabilitation. However, a search of the literature found no established guidelines for use of the 6MWT in cardiac rehabilitation. OBJECTIVES Systematic review of the validity, reliability and responsiveness of the 6MWT in cardiac rehabilitation. DATA SOURCES OvidMEDLINE, SPORTdiscus, EMBASE, CINAHL, Cochrane Reviews and Cochrane Clinical Trials between January 1948 and April 2011. ELIGIBILITY CRITERIA Studies using 6MWTs in subjects with coronary artery disease undergoing cardiac rehabilitation on an outpatient basis, published in English, were included. STUDY APPRAISAL AND METHODS: Quantitative and qualitative analyses were conducted, including quality assessment of methodology, meta-analysis and assessment against level of evidence criteria. RESULTS Fifteen articles met the inclusion criteria. One high-quality study was identified for reliability, six high-quality studies were identified for validity and 11 high-quality studies were identified for responsiveness. The meta-analysis found strong evidence that the 6MWT was responsive to change in clinical status following cardiac rehabilitation, with an estimated mean difference in 6-minute walk distance of 60.43m (95% confidence interval 54.57 to 66.30m; P<0.001). Qualitative analysis indicated moderate evidence for repeatability of the 6MWT in patients undergoing cardiac rehabilitation, for a 2% to 8% learning effect between repeated 6MWTs, for a relationship between peak heart rate during the 6MWT and during cycle exercise at the ventilatory threshold, and for moderate-to-high correlation between the 6-minute walk distance and maximum metabolic equivalents achieved on symptom-limited exercise tests. LIMITATIONS Few studies assessed similar aspects of validity for the 6MWT. CONCLUSION Strong evidence suggests that the 6MWT is responsive to clinical change following cardiac rehabilitation. Intra- and intertester reliability of the 6MWT and its validity in patients undergoing cardiac rehabilitation requires further research.