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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.

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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