The minimum clinically important improvement in the incremental shuttle walk test following cardiac rehabilitation

The aim was to establish the minimum clinically important difference (MCID) in the incremental shuttle walk test (ISWT) following cardiac rehabilitation.

This was a service evaluation, utilising anchor- and distribution-based methods.

Two hundred and twenty patients performed an ISWT following a six-week cardiac rehabilitation programme comprising supervised aerobic exercise, secondary prevention education and a home exercise programme.

Patient perception of change in ISWT distance following cardiac rehabilitation. After completing cardiac rehabilitation, subjects were asked to identify, from a five-point Likert scale, their perceived change in exercise performance (range: from ‘better’ to ‘worse’). Two distribution-based methods were also employed (standard deviation (SD) and effect size). The agreement between all measures was observed.

Mean (SD) age was 65.0 (10.5) years, body mass index 28.4 (5.1), 170 male. The baseline ISWT was 390.8 (173.1) metres (m), which increased to 456.0 (186.7) m (mean change 65.2 (95% confidence interval 55.4–74.9) m after cardiac rehabilitation (p < 0.001)). In those rating their exercise tolerance as ‘slightly better’, the mean improvement was 70.0 (95% confidence interval 51.5–88.5) m. The SD method yielded a minimum clinically important difference value of 36.65 m and the effect size for the change was 0.38. The agreement between the patients’ perception of change and distribution-based methods was poor.

The minimum clinically important difference for the ISWT following cardiac rehabilitation is 70 m. This patient-reported value is a more sensitive measure and has poor agreement with distribution-based estimates. This value may help clinicians interpret ISWT change in patients, help researchers estimate sample size and aid comparison between studies, when the ISWT is the primary outcome.