Reproducibility of the Six-Minute Walk Test in Children and Youth With Juvenile Idiopathic Arthritis.

OBJECTIVE: While the 6-minute walk test is increasingly being used in research to evaluate submaximal exercise capacity of children with juvenile idiopathic arthritis (JIA), psychometric properties with this population have not been well evaluated. We undertook this study to evaluate reproducibility (agreement and test-retest reliability) and to determine standard error of measurement (SEM) and smallest detectable difference (SDD) in children and youth with JIA. METHODS: Participants (n = 22, mean ± SD age 13.1 ± 1.1 years, 63.6% female) completed a 6-minute walk test as part of their routine clinical assessment, and then repeated the 6-minute walk test at mean ± SD 8 ± 1.2 days later, in the same clinical setting with the same rater. RESULTS: The intraclass correlation coefficient (95% confidence interval) was 0.86 (0.66-0.94); the SEM and SDD were 23.5 and 65.1 meters, respectively. CONCLUSION: These results provide evidence of good-excellent reproducibility of the 6-minute walk test with children and youth with JIA and support the use of the 6-minute walk test as a measure of submaximal exercise capacity in clinical practice and research.

Reference Values for the Six Minute Walk Test in Children with Juvenile Idiopathic Arthritis.

AIMS: To (1) describe six-minute walk test (6MWT) reference values for children with Juvenile Idiopathic Arthritis (JIA) and (2) explore predictors of 6MWT distance. A secondary objective was to determine how 6MWT distances of children with JIA compare to those of children without JIA reported in the literature. METHODS: Demographic, clinical, height, weight and 6MWT data were extracted from clinical records of 120 children with JIA (70.8% female, mean age=12.4 ± 3.2 years) who attended a follow-up rheumatology clinic. A total of 272 6MWTs were included in the analyses. Linear mixed effects modeling was used to determine the relationship between predictive variables and 6MWT distance. 6MWT distances were compared to predicted values using published equations for estimating 6MWT distances in children without JIA. RESULTS: Height, weight, and age were predictive of 6MWT distance (R2 = 0.62). Mean 6MWT distances for children with JIA were lower than those reported for children without JIA (p < 0.001). Mean 6MWT distance was 84% and 78% of predicted values for children without JIA. CONCLUSION: The reference values and associated predictive model have application for assessing exercise capacity in children with JIA.