Minimum important difference for the incremental shuttle walk test in long covid rehabilitation, 2026, Baldwin et al

[forestglip]

Minimum important difference for the incremental shuttle walk test in long covid rehabilitation

Spoiler: Authors

Baldwin, Molly M; Daynes, Enya; Evans, Rachael A; Singh, Sally J

Abstract
The minimum important difference (MID) for the incremental shuttle walk test (ISWT) in individuals with long covid was estimated using anchor-based and distribution-based methods. 397 participants (56 ± 13 years; 63.7% male) with long covid completed a 6-week rehabilitation programme and rated perceived change using the Global Rating of Change Scale (GRCS).

Change in ISWT distance differed across GCRS categories (p<0.05); participants reporting slight improvement increased ISWT distance by 60.7±85.9 m. Receiver operating characteristic analysis identified an optimal cut-off of 35 m (area under the curve 0.70, 95% CI 0.61 to 0.79; p<0.05). Distribution-based methods yielded MID estimates of 40.1 m and 52.5 m, supporting an MID range of 35–60.7 m.

Web | DOI | PDF | Thorax | Paywall

Edit: Corrected "Open Access" to "Paywall".

 

[Utsikt]

The paper is paywalled for me.

397 participants (56 ± 13 years; 63.7% male) with long covid completed a 6-week rehabilitation programme and rated perceived change using the Global Rating of Change Scale (GRCS).

This probably means that the MCID is a lot higher, because the rehab undoubtedly included psychoeducation aimed at altering responses to questionnaires in favour of having perceived an improvement.

That’s something I had not yet considered as a confounder when considering MCIDs.

 

[SNT Gatchaman]

Methods —

This evaluation included individuals with long covid who completed a 6-week centre-based COVID-19 rehabilitation programme between July 2020 and March 2024 at University Hospitals of Leicester NHS Trust. The programme comprised two times a week supervised aerobic and resistance exercise sessions, alongside education.

Immediately after the post-rehabilitation ISWT, and while blinded to their achieved distance, participants rated perceived change in exercise tolerance using the Global Rating of Change Scale (GRCS), a seven-point Likert scale from −3 (large deterioration) to +3 (large improvement), with 0 indicating no change from baseline.

Discussion —

The MID for the ISWT has been established in several chronic cardiac and respiratory conditions; however, no MID has been proposed for individuals with long covid. We used distribution-based and anchor-based methods to determine the MID in this cohort.

The distribution-based estimates were 40.1 m and 52.5 m, exceeding values previously reported for respiratory conditions, including chronic obstructive pulmonary disease (36.1 m) and interstitial lung disease (38.5 m), suggesting a more heterogeneous population.

Using an anchor-based method incorporating patient-perceived improvement, an MID of 60.7 m corresponded to participants reporting a ‘slight improvement’. This is greater than the anchor-based MID for respiratory conditions (48 m (39–57 m)) but lower than cardiac values (70 m (55–85 m)) reported in a meta-analysis of exercise-based studies.

Minimum Important Difference really is minimum here.

Patient expectations may impact perceived improvement. Unlike the gradual decline in exercise tolerance often accepted in chronic conditions, individuals with long covid may anticipate full recovery in exercise tolerance, placing greater expectations on rehabilitation outcomes and influencing GRCS responses.

Of course. The patients were expecting that rehabilitation actually works, as they've been repeatedly told. It's the standard pathway, with lots of studies.

We could not determine an MID using the EQ-5D-5L, CAT or FACIT-F as anchors. ROC analysis identified a 35 m cut-off for distinguishing between those who reported improvement and those reporting no improvement. However, the associated specificity (0.35) indicates poor discrimination of non-improved individuals

(Asking the patients if they're better vs the "validated instruments".)

 

[dave30th]

Can someone explain the difference between an anchor-based method and a distribution-based method of determining an MCID? thanks.

 

[SNT Gatchaman]

I haven't read it but they reference —

Unravelling the mystery of the ‘minimum important difference’ using practical outcome measures in chronic respiratory disease (2019)

…

In this article, we consider the concept of the MID using the example of practical outcome measures in patients with CRD. We describe the various ways in which an MID can be calculated via anchor- and distribution-based methods, looking at practical examples and considering the importance of understanding how an MID was derived when seeking to apply it to a particular situation.

…

Web | PDF | Chronic Respiratory Disease | Open Access