Determining the minimal clinically important difference for the six-minute walk test and the 200-meter fast-walk test during cardiac rehabilitation program in coronary artery disease patients after acute coronary syndrome

Objective: To estimate the minimal clinically important difference (MCID) for the 6-minute walk test (6MWT) and the 200-m fast-walk test (FWT) in patients with coronary artery disease (CAD) during a cardiac rehabilitation program.

Design: Prospective study using distribution- and anchor-based methods.

Setting: Outpatients from a cardiac rehabilitation unit.

Participants: Stable patients with CAD (N=81; 77 men; mean±SD age, 58.1±8.7y) enrolled 31±12.1 days after an acute coronary syndrome (ACS).

Interventions: Not applicable.

Main outcome measures: 6MWT and 200-m FWT results before and after an 8-week cardiac rehabilitation program and at the 6th and 12th sessions. Patients and physiotherapists who supervised the training were asked to provide a global rating of perceived change in walking ability while blinded to changes in walk test performances.

Results: Mean change in 6MWT distance (6MWD) in patients who reported no change was -6.5m versus 23.3m in those who believed their performance had improved (P<.001). This result was consistent with the MCID determined by using the distribution method (23m). Considering a 25-m cutoff, positive and negative predictive values were 0.9 and .63, respectively. Conversely, there was no difference in 200-m FWT performance between these 2 groups (0.1 vs -1.4s, respectively). There was poor agreement with the physiotherapist's perceived change.

Conclusions: The MCID for 6MWD in patients with CAD after ACS was 25m. This result will help physicians interpret 6MWD change and help researchers estimate sample sizes in further studies using 6MWD as an endpoint.