Using the Barthel Index and modified Rankin Scale as Outcome Measures for Stroke Rehabilitation Trials; A Comparison of Minimum Sample Size Requirements
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Objectives Underpowered trials risk inaccurate results. Recruitment to stroke rehabilitation randomised controlled trials (RCTs) is often a challenge. Statistical simulations offer an important opportunity to explore the adequacy of sample sizes in the context of specific outcome measures. We aimed to examine and compare the adequacy of stroke rehabilitation RCT sample sizes using the Barthel Index (BI) or modified Rankin Scale (mRS) as primary outcomes. Methods We conducted computer simulations using typical experimental event rates (EER) and control event rates (CER) based on individual participant data (IPD) from stroke rehabilitation RCTs. Event rates are the proportion of participants who experienced clinically relevant improvements in the RCT experimental and control groups. We examined minimum sample size requirements and estimated the number of participants required to achieve a number needed to treat within clinically acceptable boundaries for the BI and mRS. Results We secured 2350 IPD (18 RCTs). For a 90% chance of statistical accuracy on the BI a rehabilitation RCT would require 273 participants per randomised group. Accurate interpretation of effect sizes would require 1000s of participants per group. Simulations for the mRS were not possible as a clinically relevant improvement was not detected when using this outcome measure. Conclusions Stroke rehabilitation RCTs with large sample sizes are required for accurate interpretation of effect sizes based on the BI. The mRS lacked sensitivity to detect change and thus may be unsuitable as a primary outcome in stroke rehabilitation trials.
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BI may be a useful outcome in stroke rehabilitation RCTs with sufficient sample sizes, whereas the mRS seems to lack sensitivity to detect change and may be unsuitable as a primary outcome.
“BI may be a useful outcome in stroke rehabilitation RCTs with sufficient sample sizes to support accurate interpretation of statistical significance levels; however, the mRS seems to lack sensitivity to detect change and thus may be unsuitable as a primary outcome [67].”
From Early Occupational Therapy Intervention post-stroke (EOTIPS): A randomized controlled trial (2024) · cites this paper as [67]
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- Authors
- McGill, K., Sackley, C., Godwin, J., Gavaghan, D., Ali, M., Ballester, B. R., Brady, M. C., Brady, M. C., Ali, M., Ashburn, A., Barer, D., Barzel, A., Bernhardt, J., Bowen, A., Drummond, A., Edmans, J., English, C., Gladman, J., Godecke, E., Hiekkala, S., Hoffman, T., Kalra, L., Kuys, S., Langhorne, P., Laska, A. C., Lees, K., Logan, P., Machner, B., Mead, G., Morris, J., Pandyan, A., Pollock, A., Pomeroy, V, Rodgers, H., Sackley, C., Shaw, L., Stott, D. J., Sunnerhagen, K. S., Tyson, S., van Vliet, P., Walker, M., & Whiteley, W.
- Affiliations
- Glasgow Caledonian University (GB)
- University of Oxford (GB)
- University of Nottingham (GB)
- Institute for Bioengineering of Catalonia (ES)
- Corresponding author
- McGill, Kris
- ORCID
- McGill, Kris
- Sackley, Catherine
- Godwin, Jon
- Gavaghan, David
- Ali, Myzoon
- Ballester, Belen Rubio
- Barzel, A
- Bernhardt, J
- Bowen, A
- English, C
- Gladman, J
- Godecke, E
- Hiekkala, S
- Kuys, S
- Langhorne, P
- Laska, A.C
- Lees, K
- Logan, P
- Machner, B
- Mead, G
- Morris, J
- Pandyan, A
- Pomeroy, V
- Rodgers, H
- Stott, D.J
- Sunnerhagen, K.S
- Tyson, S
- Walker, M
- Whiteley, W
- Venue
- Journal of Stroke and Cerebrovascular Diseases
- Publisher
- Elsevier BV
- Published
- 2022-02
- Volume
- 31
- Issue
- 2
- Pages
- 106229
- ISSN
- 1052-3057 (ISSN-L)
- OpenAlex
- W3212706943
- Cited by
- 14
- References
- 40
- Citations by year
- 2026: 4 · 2025: 2 · 2024: 2 · 2023: 5 · 2022: 1
- FWCI
- 1.49
- Type
- journal article
- Language
- en
- Open access
- Licence
- Locations
- Journal of Stroke and Cerebrovascular Diseases (publishedVersion)
- PubMed (publishedVersion)
- Bournemouth University Research Online (Bournemouth University) (acceptedVersion)
- ResearchOnline (Glasgow Caledonian University) (acceptedVersion, cc-by-nc-nd)
- Discovery Research Portal (University of Dundee) (submittedVersion, cc-by-nc-nd)
- Funders
- Glasgow Caledonian University
- Scottish Government Health and Social Care Directorate
- Topics
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Health Sciences › Medicine › Rehabilitation › Stroke Rehabilitation and Recovery
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
- Keywords
- stroke rehabilitation, Barthel Index, modified Rankin Scale, sample size determination, outcome measure sensitivity, statistical power, number needed to treat, individual patient data, randomized controlled trials, functional outcome measures
- MeSH terms
- Stroke Rehabilitation, Humans, Research Design, Severity of Illness Index, Randomized Controlled Trials as Topic, Outcome Assessment, Health Care, Sample Size
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