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

Objective To examine whether peak work rate (W peak ) can predict peak oxygen uptake (V O 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 V O 2peak and W peak were determined. A multivariate regression model was used to formulate a regression equation to predict V O 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 V O 2peak was established: V O 2peak (liters/minute) = 0.308 + 0.146 × sex (0 = female, 1 = male) + 0.005 × weight (kg) + 0.008 × W peak (W) (R 2 = 0.91, standard error of the estimate = 0.18 liter/minute). Using this equation, the predicted V O 2peak was strongly related to the measured V O 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 V O 2peak in children with JIA and may be used as a surrogate measure of V O 2peak in situations where it is not possible to formally assess V O 2peak .