Background/Purpose:

The 6-minute walk test (6MWT) is a widely used measure of functional exercise capacity. It has not, however, been routinely used in pediatric rheumatology practice to date. There is little known about normative values for children with rheumatic disease, including juvenile idiopathic arthritis (JIA). The objectives of this study were to: 1) describe normative values for patients with JIA; 2) investigate which characteristics best predict 6-minute walk distance (6MWD) in this population and establish a prediction equation; and 3) compare 6MWD in patients with JIA to published values for healthy children.

Methods:

At the Glenrose Rehabilitation Hospital in Edmonton, Canada, we have been administering the 6MWT to our JIA patients every 6 months since June 2013. We performed a retrospective chart review of 116 unique patients with a total of 272 6MWTs. Each 6 MWT was administered on a 25 m track by a therapy assistant. Sex, weight, height, date of birth, testing date, JIA subtype, and lower limb involvement (active and chronic) were recorded. A mixed effects model was used to analyze the data. Univariate modelling of outcome (6MWD) vs. potential predictors was conducted. Variables with p ≤ 0.2 were selected for inclusion in the final model (cross-sectional age, longitudinal age, height and weight). To address objective 3, predicted 6MWT distances were calculated according to established prediction equations for healthy children developed by Geiger et al. (2007) and Ben Saad et al. (2009). Percentage of predicted values were calculated using actual 6MWDs.

Results:

Normative values for children with JIA are presented in Table 1. The final prediction model for our population was 6MWD = 161.45 + cross-sectional age(years)*2.33 + longitudinal age *15.86 + height (m)*2.954 – weight (kg)*1.79; r² = 0.62). All other factors, including sex, lower limb involvement, and JIA subtype were not significant and therefore were excluded from the model. The 6MWDs of children with JIA were lower than reported for typically developing children (Geiger =84%, range 59%-109% of predicted; Ben Saad = 78%, range 53% -107% of predicted).

Conclusion:

This study provides normative values and a prediction equation for the 6MWT for children with JIA. Reference values are clinically relevant as they provide a user-friendly method for the interpretation and prediction of functional exercise capacity. The characterization of functional exercise capacity in children with JIA could provide the basis for an outcome measurement in this population. The difference in 6MWD between children who are typically developing and the children with JIA shows that children with JIA have impaired functional exercise capacity.

Table 1: 6 MWT Results by Age

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/six-minute-walk-test-in-childreh-with-juvenile-idiopathic-arthritis-normative-values-prediction-equation-and-comparison-to-healthy-children/