Abstract
Background: Different reference equations are used to predict values for walked distance in the 6-min walk test (6MWT), which allows a deeper interpretation of its results. However there are no studies that analysed the agreement and responsiveness of commonly used reference equations in Brazilian patients with chronic obstructive pulmonary disease (COPD).
Objective: To analyze the agreement and responsiveness of different reference equations for the 6MWT in Brazilian patients with COPD.
Methods: 153 patients performed the 6MWT and had the predicted walked distance calculated by 6 equations commonly used in Brazil: 4 specific for Brazilian population (Iwama; Britto_1; Britto_2; Soares) and 2 for other ethnicities (Troosters; Enright). In a separate cohort, 49 patients were reassessed after a 3-month high-intensity exercise training program in order to analyze responsiveness.
Results: When classifying the walked distance as “reduced” (<80%pred), the agreement of the equations ranged from fair to good (Kappa: 0.29-0.83), with better agreement among the Brazilian equations (0.69-0.83). The 6MWT improved after the training program both in absolute (Δ=47±35m) and predicted values (7-10%pred, according to each equation) (P<0.0001 for all). All the evaluated equations presented moderate responsiveness (0.58≤ES≤0.72), without differences between international and Brazilian equations.
Conclusions: All reference equations analysed presented fair to good agreement and moderate responsiveness. However, those specific for Brazilian population had better results, corroborating international recommendations that an equation generated in a local population should be applied when possible.
- Copyright ©ERS 2015