Can peak work rate predict peak oxygen uptake in children with juvenile idiopathic arthritis?

ABSTRACT

OBJECTIVE: To examine whether peak work rate (W(peak)) can predict peak oxygen uptake (VO(2peak)) in children with juvenile idiopathic arthritis (JIA). METHODS: Ninety-one patients with JIA with a mean +/- SD age of 11.4 +/- 2.9 years underwent a cardiopulmonary exercise test in which VO(2peak) and W(peak) were determined. A multivariate regression model was used to formulate a regression equation to predict VO(2peak) using W(peak) and anthropometric and demographic details. This regression equation was subsequently cross-validated using an unrelated data set from children with JIA (n = 17). RESULTS: The following linear regression equation to predict VO(2peak) was established VO(2peak) (liters/minute) = 0.308 + 0.146 x sex (0 = female, 1 = male) + 0.005 x weight (kg) + 0.008 x W(peak) (W) (R(2) = 0.91, standard error of the estimate = 0.18 liter/minute). Using this equation, the predicted VO(2peak) was strongly related to the measured VO(2peak) (r = 0.96, P < 0.0001). Bland and Altman analysis revealed a mean difference of 0.01 liter/minute and limits of agreement between -0.35 and 0.35 liter/minute. CONCLUSION: This study suggests that W(peak) is a strong predictor of VO(2peak) in children with JIA and may be used as a surrogate measure of VO(2peak) in situations where it is not possible to formally assess VO(2peak).