Concurrent validity between field tests and cardiopulmonary exercise testing in patients with idiopathic pulmonary fibrosis

Background: Maximal treadmill cardiopulmonary exercise testing is the gold standard for assessing functional capacity in patients with idiopathic pulmonary fibrosis (IPF). Purpose: Primarily to investigate the concurrent validity between three field tests and cardiopulmonary exercise testing in these patients. Methods: Patients performed the cardiopulmonary exercise testing, a six-minute walk test, an incremental shuttle walk test, and, the Glittre-ADL test. For cardiopulmonary exercise testing, the ten seconds with the higher average of the peak oxygen uptake obtained within the last 30 seconds were considered; for six-minute walk test and incremental shuttle walk test, the longer distance; and for the Glittre-ADL test, the shorter time spent. Concurrent validity was assessed using different regression models based on the best adjustment of the data. Results: Twenty-two patients with IPF were assessed, aged: 68 +/- 8.1 years, 13 male. Patients presented a peak oxygen uptake of 16.5 +/- 3.6 mL.kg(-1.)min(1), achieving a distance of 512.6 +/- 102.8 meters in the six-minute walk test and 415.7 +/- 125.1 meters in incremental shuttle walk test. The walking distance in the six-minute walk test and the incremental shuttle walk test explained, respectively, 64% and 56% peak oxygen uptake variance observed in the cardiopulmonary exercise testing (R-2 = 0.64,p < .001; R-2 = 0.56,p < .001). The time spent in the Glittre-ADL test was 233.4 +/- 88.7 seconds and explained 47% of the peak oxygen uptake variance observed in cardiopulmonary exercise testing (R-2 = 0.47,p = .001). Conclusion: The six-minute walk test, incremental shuttle walk test, and Glittre-ADL test were considered valid tests to explain the peak oxygen uptake variance obtained by the cardiopulmonary exercise testing in patients with IPF.