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The six-minute walking test in children with cystic fibrosis: reliability and validity
V A Gulmans1, N H van Veldhoven, K de Meer
1Department of Pediatric Physiotherapy, University Children's Hospital Wilhelmina Kinderziekenhuis, Utrecht, The Netherlands.
Insights
The 6-minute walking test is a reproducible and valid tool for assessing exercise tolerance in children with cystic fibrosis (CF). This simple test correlates well with more complex exercise measures, aiding in the evaluation of CF patients.
Area of Science:
- Pediatric Pulmonology
- Exercise Physiology
- Clinical Assessment
Background:
- Assessing exercise tolerance in children with cystic fibrosis (CF) is crucial for managing daily activity and guiding specialized testing.
- The 6-minute walking test (6MWT) offers a practical simulation of normal childhood physical activity.
Purpose of the Study:
- To evaluate the reproducibility and validity of the 6-minute walking test in children with mild to moderate cystic fibrosis.
- To determine if the 6MWT can serve as a reliable measure of exercise tolerance and endurance in this population.
Main Methods:
- Part A: Assessed reproducibility of the 6MWT in 23 children with mild CF by conducting two tests one week apart.
- Part B: Evaluated validity in 15 children with moderate CF by comparing 6MWT results with standardized maximum incremental exercise testing on a cycle ergometer.
Main Results:
- The 6MWT demonstrated high reproducibility in children with mild CF (r=0.90).
- Significant correlations were found between 6MWT distance and maximum workload (r=0.76) and maximum oxygen uptake (r=0.76) in children with moderate CF.
- Pulmonary hyperinflation (RV/TLC ratio) negatively correlated with walking distance (r=-0.72).
Conclusions:
- The 6-minute walking test is a valid, reproducible, and useful tool for assessing exercise tolerance and endurance in children with mild to moderate cystic fibrosis.
- The test provides a practical alternative to laboratory-based exercise testing for evaluating functional capacity in pediatric CF patients.
Abstract:
There is a need to judge general exercise tolerance in children with cystic fibrosis (CF) under normal daily activity conditions and -when more extensive testing is required-in an exercise laboratory in a specialized center. We investigated the reproducibility, validity, and criterion for a 6-minute walking test, which simulates normal childhood activities. In Part A, we evaluated the reproducibility of a 6-minute walking test in 23 children (12 girls and 11 boys; ages 11.1 +/- 2.2 years; range, 8.2 15.6 years) with mild symptoms of CF [forced expiratory volume in 1 second (FEV1) 94.4 +/- 16.5% of predicted values (range, 60.6-129.7); body weight Z-score -0.71 +/- 0.81 (range, -1.73-0.93)]. The subjects performed two standardized 6-minute walking tests with 1 week between tests. There was no significant difference between the two walking distances reached (737 +/- 85 versus 742 +/- 90 meters; P = 0.56), and there was a strong correlation between the two walking distances reached by the individuals (r = 0.90, P < 0.0001). In Part B, the validity of the walking test was evaluated in 15 children (6 girls and 9 boys; ages 14.5 +/- 2.0 years; range, 10.2-16.9 years) with moderate symptoms of CF [FEV1 = 58 +/- 16.0% of predicted values, (range, 41.1-89.4); RV/TLC ratio = 46.3 +/- 6.5% (range, 31.6-57.2); body weight Z-score: -1.29 +/- 0.60 (range, -2.20-0.14)]. They underwent standardized maximum incremental exercise testing on a cycle ergometer and a 6-minute walking test. Postexertional lactate values exceeded threshold values (as described in the literature) in all patients but one. Correlation analysis (Pearson) showed a significant correlation between the walking distance reached (WD = 697 +/- 104 meters), and the maximum workload (Wmax = 118 +/- 44 watt; r = 0.76, P < 0.001) or the maximum oxygen uptake (1,688 +/- 495 ml; r = 0.76, P < 0.001), the latter two being determined on a cycle ergometer, RV/TLC% showed a significant negative correlation (r = -0.72, P < 0.01) with WD. Stepwise multiple regression analysis showed a multiple regression coefficient of R = 0.84 (P < 0.001) for Wmax and RV/TLC % as the independent variables vs. WD as the dependent variable. We conclude that the 6-minute walking test is a valid and useful test in children with mild to moderate symptoms of CF to assess their exercise tolerance and endurance. Exercise test results correlated negatively with pulmonary hyperinflation expressed by the RV/TLC ratio.