Napasri Chaisinanunkul1, Opeolu Adeoye1, Roger J Lewis1, James C Grotta1, Joseph Broderick1, Tudor G Jovin1, Raul G Nogueira1, Jordan J Elm1, Todd Graves1, Scott Berry1, Kennedy R Lees1, Andrew D Barreto1, Jeffrey L Saver2. 1. From the Department of Neurology and Comprehensive Stroke Center, University of California, Los Angeles (N.C., J.L.S.); Phyathai Stroke Center, Department of Neurology, Phyathai 1 Hospital, Bangkok, Thailand (N.C.); Departments of Emergency Medicine and Neurosurgery, Neuroscience Institute (O.A.) and Department of Neurology and Rehabilitation Medicine (J.B.), University of Cincinnati, OH; Department of Emergency Medicine at Harbor-UCLA Medical Center, Berry Consultants, LLC, Austin, TX (R.J.L.); Clinical Innovation & Research Institute, Memorial Hermann Hospital-Texas Medical Center, Houston (J.C.G.); Department of Neurology, University of Pittsburgh Medical Center, PA (T.G.J.); Department of Neurology, Marcus Stroke and Neuroscience Center, Grady Memorial Hospital, Emory University, Atlanta, GA (R.G.N.); Department of Public Health Sciences, Medical University of South Carolina, Charleston (J.J.E.); Berry Consultants, LLC, Austin, TX (T.G., S.B.); Department of Stroke Research, University of Glasgow, Glasgow, United Kingdom (K.R.L.); and Department of Neurology, Stroke Division, University of Texas Health Science Center at Houston (A.D.B.). 2. From the Department of Neurology and Comprehensive Stroke Center, University of California, Los Angeles (N.C., J.L.S.); Phyathai Stroke Center, Department of Neurology, Phyathai 1 Hospital, Bangkok, Thailand (N.C.); Departments of Emergency Medicine and Neurosurgery, Neuroscience Institute (O.A.) and Department of Neurology and Rehabilitation Medicine (J.B.), University of Cincinnati, OH; Department of Emergency Medicine at Harbor-UCLA Medical Center, Berry Consultants, LLC, Austin, TX (R.J.L.); Clinical Innovation & Research Institute, Memorial Hermann Hospital-Texas Medical Center, Houston (J.C.G.); Department of Neurology, University of Pittsburgh Medical Center, PA (T.G.J.); Department of Neurology, Marcus Stroke and Neuroscience Center, Grady Memorial Hospital, Emory University, Atlanta, GA (R.G.N.); Department of Public Health Sciences, Medical University of South Carolina, Charleston (J.J.E.); Berry Consultants, LLC, Austin, TX (T.G., S.B.); Department of Stroke Research, University of Glasgow, Glasgow, United Kingdom (K.R.L.); and Department of Neurology, Stroke Division, University of Texas Health Science Center at Houston (A.D.B.). jsaver@mednet.ucla.edu.
Abstract
BACKGROUND AND PURPOSE: Although the modified Rankin Scale (mRS) is the most commonly used primary end point in acute stroke trials, its power is limited when analyzed in dichotomized fashion and its indication of effect size challenging to interpret when analyzed ordinally. Weighting the 7 Rankin levels by utilities may improve scale interpretability while preserving statistical power. METHODS: A utility-weighted mRS (UW-mRS) was derived by averaging values from time-tradeoff (patient centered) and person-tradeoff (clinician centered) studies. The UW-mRS, standard ordinal mRS, and dichotomized mRS were applied to 11 trials or meta-analyses of acute stroke treatments, including lytic, endovascular reperfusion, blood pressure moderation, and hemicraniectomy interventions. RESULTS: Utility values were 1.0 for mRS level 0; 0.91 for mRS level 1; 0.76 for mRS level 2; 0.65 for mRS level 3; 0.33 for mRS level 4; 0 for mRS level 5; and 0 for mRS level 6. For trials with unidirectional treatment effects, the UW-mRS paralleled the ordinal mRS and outperformed dichotomous mRS analyses. Both the UW-mRS and the ordinal mRS were statistically significant in 6 of 8 unidirectional effect trials, whereas dichotomous analyses were statistically significant in 2 to 4 of 8. In bidirectional effect trials, both the UW-mRS and ordinal tests captured the divergent treatment effects by showing neutral results, whereas some dichotomized analyses showed positive results. Mean utility differences in trials with statistically significant positive results ranged from 0.026 to 0.249. CONCLUSIONS: A UW-mRS performs similar to the standard ordinal mRS in detecting treatment effects in actual stroke trials and ensures the quantitative outcome is a valid reflection of patient-centered benefits.
BACKGROUND AND PURPOSE: Although the modified Rankin Scale (mRS) is the most commonly used primary end point in acute stroke trials, its power is limited when analyzed in dichotomized fashion and its indication of effect size challenging to interpret when analyzed ordinally. Weighting the 7 Rankin levels by utilities may improve scale interpretability while preserving statistical power. METHODS: A utility-weighted mRS (UW-mRS) was derived by averaging values from time-tradeoff (patient centered) and person-tradeoff (clinician centered) studies. The UW-mRS, standard ordinal mRS, and dichotomized mRS were applied to 11 trials or meta-analyses of acute stroke treatments, including lytic, endovascular reperfusion, blood pressure moderation, and hemicraniectomy interventions. RESULTS: Utility values were 1.0 for mRS level 0; 0.91 for mRS level 1; 0.76 for mRS level 2; 0.65 for mRS level 3; 0.33 for mRS level 4; 0 for mRS level 5; and 0 for mRS level 6. For trials with unidirectional treatment effects, the UW-mRS paralleled the ordinal mRS and outperformed dichotomous mRS analyses. Both the UW-mRS and the ordinal mRS were statistically significant in 6 of 8 unidirectional effect trials, whereas dichotomous analyses were statistically significant in 2 to 4 of 8. In bidirectional effect trials, both the UW-mRS and ordinal tests captured the divergent treatment effects by showing neutral results, whereas some dichotomized analyses showed positive results. Mean utility differences in trials with statistically significant positive results ranged from 0.026 to 0.249. CONCLUSIONS: A UW-mRS performs similar to the standard ordinal mRS in detecting treatment effects in actual stroke trials and ensures the quantitative outcome is a valid reflection of patient-centered benefits.
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