Prognostic value of variables derived from the six-minute walk test in patients with COPD: Results from the ECLIPSE study

Abstract

In addition to the six-min walk distance (6 MWD), other six-min walk test (6 MWT) derived variables, such as mean walk-speed (6MWSpeed), 6-min walk-work (6 MWW), distance-saturation product (DSP), exercise-induced oxygen desaturation (EID), and unintended stops may be useful for the prediction of mortality and hospitalization in patients with chronic obstructive pulmonary disease (COPD). We studied the association between 6 MWT-derived variables and mortality as well as hospitalization in COPD patients and compared it with the BODE index.A three-year prospective study (ECLIPSE) to evaluate the prognostic value of 6 MWT-derived variables in 2010 COPD patients. Cox's proportional-hazard regressions were performed to estimate 3-year mortality and hospitalization.During the follow-up, 193 subjects died and 622 were hospitalized. An adjusted Cox's regression model of hazard ratio [HR] for impaired 6 MWT-derived variables was significant referring to: mortality (6 MWD ≤334 m [2.30], 6MWSpeed ≤0.9 m/sec [2.15], 6 MWW ≤20000 m kg [2.17], DSP ≤290 m% [2.70], EID ≤88% [1.75], unintended stops [1.99]; and hospitalization (6 MWW ≤27000 m kg [1.23], EID ≤88% [1.25], BODE index ≥3 points [1.40]; all p ≤ 0.05).The 6 MWT-derived variables have an additional predictive value of mortality in patients with COPD. The 6 MWW, EID and the BODE index refine the prognosis of hospitalization.