Fifteen studies were included in the review. Of these, two studies assessed reliability (nine and 94 participants; one was high quality); eight assessed validity (sample size range 10 to 630; six were high quality); and 12 assessed responsiveness (sample size range 18 to 982; 11 were high quality).
Meta-analysis revealed strong evidence on responsiveness of the 6-minute walk test to changes in the clinical status of participants following cardiac rehabilitation. Results revealed an estimated mean difference in 6-minute walk distance of 60.43m (95% CI 54.57 to 66.30 metres; 14 studies; Ι²=60%) and this was statistically significant (p<0.001). The median effect size was 0.65.
There was moderate evidence to demonstrate the reliability of the 6-minute walk test, with an intra-class correlation coefficient of 0.97 and a 2% to 8% test-retest change (two studies). Moderate evidence was found for validity of the test, with correlations ranging from 0.56 to 0.93 in relation to maximum power, oxygen uptake and maximum metabolic equivalents during symptom-limited exercise tests. Two moderate/high quality studies found positive relationships between the test and peak heart rate at the ventilatory threshold during cycle exercise. Two of three moderate/high quality studies found moderate correlations (ranging from 0.54 to 0.62) between the 6-minute walking test and health and function outcomes, when quality-of-life questionnaires were used as reference tests. Other results for test validity were limited or inconclusive.
Further results on the discriminative ability of the test were reported in the paper.