Minimal detectable change in six-minute walk test in children and adolescents with cystic fibrosis

Abstract

Purpose To provide test-retest reliability for the 6-min walk test and the physiological variables obtained during the test, and to establish the minimal detectable change for the distance walked in children and adolescents with cystic fibrosis. Methods 40 patients performed two 6-min walk tests on the same day (separated by 30-min of rest). The perceived breathlessness and fatigue in the legs were assessed with the modified Borg scale. The peripheral muscle strength was assessed using a hand dynamometer device, the medicine ball throw test and the horizontal jump test. Results The test-retest reliability of the distance walked, dyspnea and fatigue in the legs were good for children (minimal detectable change90–95: 59.39–70.55 m) and for adolescents (minimal detectable change90–95: 47.81–56.8 m) with cystic fibrosis. Exercise tolerance is more related to 6-min walk work (distance walked x body weight) than to the distance walked alone and showed a positive association with peripheral muscle strength and forced vital capacity. Conclusions The 6-min walk test is a reproducible and reliable tool to measure exercise tolerance for children and adolescents with cystic fibrosis. The minimal detectable changes reported for the distances achieved by these patients will be useful to identify the effectiveness of therapies aimed at alleviating or improving impaired physical capacity. IMPLICATIONS FOR REHABILITATION The 6-min walk test could be used to measure exercise tolerance for children and adolescents with cystic fibrosis, as it is a reliable test over time. An increase in the distance covered in the 6-min walk test that exceeds the minimum detectable change is recommended to determine improved exercise tolerance for children and adolescents with cystic fibrosis. The use of the 6-min walk work (distance walked x body weight) is recommended because it correlates better with exercise tolerance than the distance alone in children and adolescents with cystic fibrosis.