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Response by Hawe et al to Letter Regarding Article, “Taking Proportional Out of Stroke Recovery”

2019; Lippincott Williams & Wilkins; Volume: 50; Issue: 5 Linguagem: Inglês

10.1161/strokeaha.119.024794

1524-4628

Rachel L. Hawe, Stephen H. Scott, Sean P. Dukelow,

Cardiac Health and Mental Health

HomeStrokeVol. 50, No. 5Response by Hawe et al to Letter Regarding Article, "Taking Proportional Out of Stroke Recovery" Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBResponse by Hawe et al to Letter Regarding Article, "Taking Proportional Out of Stroke Recovery" Rachel L. Hawe, DPT, PhD Stephen H. Scott, PhD Sean P. Dukelow, MD, PhD Rachel L. HaweRachel L. Hawe Department of Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Canada Stephen H. ScottStephen H. Scott Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada Sean P. DukelowSean P. Dukelow Department of Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Canada Originally published20 Mar 2019https://doi.org/10.1161/STROKEAHA.119.024794Stroke. 2019;50:e126Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: March 20, 2019: Ahead of Print In Response:We thank Drs Byblow and Stinear for their interest in our commentary regarding problems with proportional recovery: the idea that most individuals recover ≈70% of their maximal potential poststroke. Support for this concept is based on linear regressions between initial impairment and change. Our commentary showed that evidence for proportional recovery is flawed for statistical reasons due to coupling between independent and dependent variables.1 We show simulations assuming random recovery commonly predict 70% proportional recovery. Ceiling effects and nonlinear clinical scales create additional problems. We respectfully disagree with their suggestion that proportional recovery was not intended for prediction, as the initial paper introducing the approach concluded "impairment in the first 72 hours…is a very good predictor of recovery when high initial impairment outliers are removed."2 Subsequent papers also use predictive language to describe proportional recovery.Byblow and Stinear's work added to long-standing evidence that individuals with motor-evoked potentials (MEP+) typically recover more than MEP− individuals.3 They highlight that the variance accounted for in their regression for MEP+ subjects was >0.91, higher than our simulations predicted. However, their sample sizes were relatively small (≈40). If we repeat our simulations for 40 subjects, the variance explained can be >0.90. Their larger subsequent study of 136 MEP+ subjects found an R2 of 0.868,4 well within our estimates based on random recovery (Figure 3D1).Importantly, even if the variance explained by regressing initial impairment versus change is slightly above that predicted by random recovery simulations, it does not mean the slope accurately describes the amount of recovery of individuals, nor that the measure of variance is meaningful. By computing the ratio between observed recovery versus potential recovery for each subject, we found recovery to be highly variable (SD=33.4%) across subjects (Figure 4), despite an R2 of 0.86.1 The field must use a technique to quantify stroke recovery other than regressing initial impairment against change.In their letter, Byblow and Stinear state that MEP+ and MEP− individuals have distinct recovery profiles. We respectfully disagree that they are completely distinct. In the Byblow 2015 paper, 3 of 10 MEP− individuals displayed levels of recovery similar to MEP+ subjects.3 Caution is also warranted regarding generalizability of these findings due to the small sample and underrepresentation of subjects with severe impairments and good recovery compared to the larger dataset we compiled. Further studies with larger cohorts are needed to validate this important biomarker independent of proportional recovery.While the focus of our commentary was to highlight the statistical problems behind proportional recovery, Byblow and Stinear raise the concern that "current practice does not meaningfully interact with the spontaneous biological processes responsible for recovery." We think this apparent dissociation between recovery and intervention reflects the minimal amount of therapy in some studies.3,4 In Byblow et al, the majority of participants in the variable dose group received under 2 hours of therapy, with the maximum dose being 13 hours.3 The universality of 70% proportional recovery across health care systems has also been taken as evidence for proportional recovery being a spontaneous process.3 We refer back to our demonstration that 70% proportional recovery is essentially inevitable due to statistical issues.1 We remain optimistic that intensive and tailored interventions can make a difference. Importantly, future studies should not rely on calculating differences in proportional recovery across groups given the results will inevitably compress toward 70% recovery.Rachel L. Hawe, DPT, PhDDepartment of Clinical NeurosciencesHotchkiss Brain InstituteUniversity of CalgaryCanadaStephen H. Scott, PhDDepartment of Biomedical and Molecular SciencesQueen's UniversityKingston, CanadaSean P. Dukelow, MD, PhDDepartment of Clinical NeurosciencesHotchkiss Brain InstituteUniversity of CalgaryCanadaDisclosuresNone.FootnotesStroke welcomes Letters to the Editor and will publish them, if suitable, as space permits. Letters must reference a Stroke published-ahead-of-print article or an article printed within the past 4 weeks. The maximum length is 750 words including no more than 5 references and 3 authors. Please submit letters typed double-spaced. Letters may be shortened or edited.References1. Hawe RL, Scott SH, Dukelow SP. Taking proportional out of stroke recovery.Stroke. 2019; 50:204–211.LinkGoogle Scholar2. Prabhakaran S, Zarahn E, Riley C, Speizer A, Chong JY, Lazar RM, et al. Inter-individual variability in the capacity for motor recovery after ischemic stroke.Neurorehabil Neural Repair. 2008; 22:64–71. doi: 10.1177/1545968307305302CrossrefMedlineGoogle Scholar3. Byblow WD, Stinear CM, Barber PA, Petoe MA, Ackerley SJ. Proportional recovery after stroke depends on corticomotor integrity.Ann Neurol. 2015; 78:848–859. doi: 10.1002/ana.24472CrossrefMedlineGoogle Scholar4. Stinear CM, Byblow WD, Ackerley SJ, Smith MC, Borges VM, Barber PA. Proportional motor recovery after stroke: implications for trial design.Stroke. 2017; 48:795–798. doi: 10.1161/STROKEAHA.116.016020LinkGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetailsCited ByBowman H, Bonkhoff A, Hope T, Grefkes C and Price C (2021) Inflated Estimates of Proportional Recovery From Stroke, Stroke, 52:5, (1915-1920), Online publication date: 1-May-2021. May 2019Vol 50, Issue 5 Advertisement Article InformationMetrics © 2019 American Heart Association, Inc.https://doi.org/10.1161/STROKEAHA.119.024794PMID: 30890110 Originally publishedMarch 20, 2019 PDF download Advertisement SubjectsRehabilitation