Unreported summary statistics in trial publications and risk of bias in stroke rehabilitation systematic reviews: an international survey of review authors and examination of practical solutions

Christopher J. Weir, Valentina Assi, Lumine Na, Stephanie C. Lewis, Gordon D. Murray, Peter Langhorne, Marian C. Brady

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Objective: Continuous outcome measures are essential in rehabilitation research. Incomplete reporting of their mean and standard deviation, required for meta-analysis, potentially introduces bias and imprecision if it prevents studies being included. We aimed to determine how often systematic reviewers encounter missing mean or standard deviation values and to recommend practical statistical solutions.

Design: 1. Cross-sectional survey of systematic review authors. 2. Reanalysis of Cochrane review data to evaluate how accurately statistical methods for recovering missing mean or standard deviation values estimate the true meta-analysis treatment effect.

Setting: Rehabilitation intervention systematic reviews.

Participants: Cochrane stroke rehabilitation review authors; stroke patients.

Interventions: Reanalysis of a Cochrane review of early supported discharge services.

Main measures: Hospital length of stay.

Results: Survey responses covered 53 of 70 Cochrane reviews. Almost all studied continuous outcome measures, 68% encountering missing summary statistics. Various solutions were attempted but 76% of meta-analyses omitted at least one study due to missing information. In the review reanalysis (N = 1055), a method based on the minimum and maximum performed best in recovering missing standard deviations; a method based on the median, lower and upper quartiles successfully estimated a missing mean.

Conclusion: Practical statistical methods help reduce risk of bias, maximise the evidence included in rehabilitation meta-analyses and offer a clear hierarchy of solutions to handling unreported mean and standard deviation values.
Original languageEnglish
Pages (from-to)136-142
JournalJournal of Stroke Medicine
Issue number2
Early online date30 Oct 2019
Publication statusPublished - 1 Dec 2019



  • continuous outcomes
  • meta-analysis
  • missing mean
  • missing standard deviation
  • stroke rehabilitation

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