Is outdoor use of the six-minute walk test with a global positioning system in stroke patients' own neighbourhoods reproducible and valid?
To examine the reproducibility, responsiveness and concurrent validity of the six-minute walk test (6MWT) when tested outdoors in patients' own neighbourhoods using a global positioning system (GPS) or a measuring wheel. A total of 27 chronic stroke patients, discharged to their own homes, were tested twice, within 5 consecutive days. The 6MWT was conducted using a GPS and an measuring wheel simultaneously to determine walking distance. Reproducibility was determined as test-retest reliability and agreement, using the intraclass correlation coefficient, standard error of measurement and Bland & Altman plots. Responsiveness was expressed as the smallest real difference and visualized in Bland & Altman plots. Pearson's correlation coefficient (r) was used to study concurrent validity between the GPS and measuring wheel. Intraclass correlation coefficiens were 0.96 for the GPS and 0.98 for the measuring wheel, and standard error of measurement scores were 11.9 m for the measuring wheel and 18.1 m for the GPS, resulting in smallest real differences of 33.0 m and 50.2 m, respectively. Concurrent validity was strong (r = 0.99). These results indicate that the outdoor 6MWT using a GPS or measuring wheel is reproducible, responsive and concurrently valid. This suggests that therapists working in the community can use the outdoor 6MWT as a reliable, responsive and valid test.