Determining the minimum important differences for field walking tests in adults with long-term conditions: a systematic review and meta-analysis

Abstract

Importance: The minimum important difference (MID) for field walking tests aims to improve interpretation of outcomes, but the volume and heterogeneity of MIDs for these tests is challenging. We aimed to determine the MID for the 6-min walk distance (6MWD), incremental shuttle walk test (ISWT) and endurance shuttle walk test (ESWT) in adults with long-term conditions.

Methods: This systematic review included studies that generated a MID using an anchor-based approach in patients with long-term conditions for the 6MWD, ISWT or ESWT field walking tests. Studies were screened and data extracted by independent reviewers. Meta-analyses were performed using RevMan.

Results: 42 studies were included in the analyses, involving n=13 949 participants. Of these, 12 studies involving exercise as an intervention were included in the meta-analyses to produce MIDs, presented as mean (95% confidence interval). The MID for the 6MWD was 25 m (24-26 m) for respiratory conditions, 23 m (8-37 m) for cardiac conditions and 37 m (26-49 m) for neurological/musculoskeletal conditions. The MID for the ISWT was 48 m (39-57 m) for respiratory conditions and 70 m (55-85 m) for cardiac conditions. The MID for ESWT in COPD was 159 s (94-224 s). The pooled MID across conditions within exercise interventions was 26 m (22-40 m) for the 6MWD and 53 m (44-62 m) for the ISWT, with reasonable heterogeneity (I²=48% and I²=47%, respectively).

Conclusion: We propose new MIDs for exercise interventions using anchor-based methodology in long‑term conditions for the 6MWD, ISWT and ESWT. These can be used internationally for meta‑analyses where studies have used different field walking tests, to optimise trial sample size calculations, and for clinical service benchmarking.

FIGURE 1

Consort diagram of included studies. 6MWD: 6-min walk distance; ESWT: endurance shuttle walk test; ISWT: incremental shuttle walk test; MID: minimum important difference.

FIGURE 2

Forest plot of the 6-min walk distance minimum important difference (MID) calculated in exercise-based interventions. IV: inverse weighted; se: standard error.

FIGURE 3

Forest plot of the incremental shuttle walk test minimum important difference (MID) calculated in exercise-based interventions. IV: inverse weighted; se: standard error.

FIGURE 4

Forest plot of the endurance shuttle walk test minimum important difference (MID) calculated in exercise-based interventions. IV: inverse weighted; se: standard error.