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Quantifying the value of stroke disability outcomes: WHO global burden of disease project disability weights for each level of the modified Rankin Scale.

ABSTRACT: The modified Rankin Scale (mRS) categorizes poststroke disability among 7 broad, ordinal grades, but the interval distances between these levels are spaced along the disability spectrum have not been previously investigated.We used the person trade-off procedure developed by the World Health Organization Global Burden of Disease Project (WHO-GBDP) to generate disability weights (DWs) ranging from 0 (normal) to 1 (dead) for each of 7 mRS grades. The ratings of an international, 9-member panel of stroke experts were combined by a modified Delphi process.DWs (95% CI) were 0 for mRS 0, 0.046 (0.004 to 0.088) for mRS 1, 0.212 (0.175 to 0.250) for mRS 2, 0.331 (0.292 to 0.371) for mRS 3, 0.652 (0.625 to 0.678) for mRS 4, 0.944 (0.873 to 1.015) for mRS 5, and 1.0 for mRS 6. DWs of adjacent mRS levels were significantly different (P<0.001 for all). Coefficients of variation showed a high degree of consensus for DWs among panel members. DWs placed each of the 5 intermediate mRS states in different disability class levels of the WHO-GBDP anchor conditions and identified natural clusters to use when reducing the mRS to fewer categories.Formal DW assignment confirms that the mRS is an ordered but unequally spaced scale. The availability of DWs for each mRS level now permits direct comparison of each poststroke outcome state with the outcomes of hundreds of other diseases in the WHO-GBDP and the expression of stroke burden in different populations by using the uniform metric of disability-adjusted life-years lost.

SUBMITTER: Hong KS

PROVIDER: S-EPMC2788070 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Quantifying the value of stroke disability outcomes: WHO global burden of disease project disability weights for each level of the modified Rankin Scale.

Hong Keun-Sik KS Saver Jeffrey L JL

Stroke 20091001 12

<h4>Background and purpose</h4>The modified Rankin Scale (mRS) categorizes poststroke disability among 7 broad, ordinal grades, but the interval distances between these levels are spaced along the disability spectrum have not been previously investigated.<h4>Methods</h4>We used the person trade-off procedure developed by the World Health Organization Global Burden of Disease Project (WHO-GBDP) to generate disability weights (DWs) ranging from 0 (normal) to 1 (dead) for each of 7 mRS grades. The ...[more]

PMID: 19797698

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Project description:BackgroundOrdinal/shift analyses of ordered measures like the modified Rankin Scale(mRS) are underused as primary trial outcomes for neurological disorders - despite statistical advantages - potentially hindered by poor clinical interpretability versus dichotomies, and by valuing state-transitions equally (linear scale). Weighted ordinal analyses incorporating step-changes at key transitions might have greater statistical validity and clinical applicability.MethodsIn a prospective population-based cohort of ischaemic stroke (Oxford Vascular Study, recruited 2002-2014), we stratified 5-year outcomes of death, dementia, and/or institutionalization, health/social-care costs, and EuroQol-derived quality-adjusted life-expectancy(QALE) by 3-month mRS. We compared root-mean-square errors(RMSEs) from linear regressions for these outcomes with the mRS coded as a linear scale versus incorporating a spline at transitions 1-2, 2-3, or 3-4. We derived 3-month mRS weights for probability of 5-year death/dementia/institutionalization using age/sex-adjusted logistic regressions, and cost and QALE weights from 1000-bootstraps. We applied these weights to analyse recent trials of thrombectomy for acute ischaemic stroke.FindingsAmong 1,607 patients, a non-linear (S-shaped) relationship was observed between 3-month mRS and each 5-year outcome, with RMSEs 18-73% lower using a spline at mRS 2-3 versus a linear representation. Age/sex-adjusted probability weights for 5-year death/dementia/institutionalization were: mRS 0=0.19; 1=0.27; 2=0.41; 3=0.73; 4=0.77; 5=0.94 (mRS 6=1 by definition). Similar trends were seen with costs; estimated 5-year QALEs were: mRS 0=3.88; 1=3.49; 2=3.01; 3=1.87; 4=1.30; 5=0.06; 6=0. Results were similar stratifying by age/sex, and excluding pre-morbidly disabled patients. Using a weighted ordinal approach, estimates of thrombectomy impact were more favourable than estimates with dichotomous approaches, 5-year cost reductions being 29% higher than with 0-2/3-6, and over three-fold higher than with 0-1/2-6 dichotomy.InterpretationOur findings favour weighting the mRS in ordinal analyses for stroke and other neurological disorders, as state-transitions differ in clinical prognosis, quality-of-life, and costs. These weights could also be used for prognostication and cost-effectiveness analyses.FundingWellcome Trust, Wolfson Foundation, NIHR Oxford Biomedical Research Centre, Rhodes Trust.

Project description:Background and objectivesPrecise measurement of outcomes is essential for stroke trials and clinical care. Prior research has highlighted conceptual differences between global outcome measures such as the modified Rankin Scale (mRS) and domain-specific measures (e.g., motor, sensory, language or cognitive function). This study related motor phenotypes to the mRS, specifically aiming to determine whether mRS levels distinguish motor impairment and function phenotypes, and to compare mRS outcomes to meaningful changes in impairment and function from acute to subacute recovery after stroke.MethodsPatients with upper extremity weakness after ischemic stroke were assessed with a battery of impairment and functional measures within the first week and at 90 days after stroke. Impairment and functional outcomes were examined in relation to 90-day mRS scores. Clinically meaningful changes in motor impairment, activities of daily living, and mobility were examined in relation to 90-day mRS score.ResultsIn this cohort of 73 patients with stroke, impairment and functional outcomes were associated with 90-day mRS scores but showed substantial variability within individual mRS levels: within mRS level 2, upper extremity impairment ranged from near hemiplegia (with an upper extremity Fugl-Meyer score 8) to no deficits (upper extremity Fugl-Meyer score 66). Overall, there were few differences in impairment and functional outcomes between adjacent mRS levels. While some outcome measures were significantly different between mRS levels 3 and 4 (Nine-Hole Peg, Leg Motor, gait velocity, Timed Up and Go, NIH Stroke Scale, and Barthel Index), none of the outcome measures differed between mRS levels 1 and 2. Fugl-Meyer and grip strength were not different between any adjacent mRS levels. A substantial number of patients experienced clinically meaningful changes in impairment and function in the first 90 days after stroke but did not achieve good mRS outcome (mRS score ≤ 2).DiscussionThe mRS broadly relates to domain-specific outcomes after stroke, confirming its established value in stroke trials, but it does not precisely distinguish differences in impairment and function, nor does it sufficiently capture meaningful clinical changes across impairment, activities of daily living status, and mobility. These findings underscore the potential utility of incorporating detailed phenotypic measures along with the mRS in future stroke trials.

Dataset Information

Quantifying the value of stroke disability outcomes: WHO global burden of disease project disability weights for each level of the modified Rankin Scale.

Publications

Quantifying the value of stroke disability outcomes: WHO global burden of disease project disability weights for each level of the modified Rankin Scale.

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