Utility-Weighted Modified Rankin Scale as Primary Outcome in Stroke Trials: A Simulation Study

Area of Science:

• Neurology
• Clinical Trials
• Health Economics

Background:

• The utility-weighted modified Rankin Scale (UW-mRS) is a proposed patient-centered outcome for stroke trials.
• Assessing the statistical efficiency of UW-mRS compared to other methods is crucial for trial design.

Purpose of the Study:

• To describe utility weights for modified Rankin Scale (mRS) health states.
• To evaluate the statistical efficiency of UW-mRS in detecting treatment effects in stroke intervention trials.

Main Methods:

• Utilized data from 500 patients in the MR CLEAN trial.
• Elicited utility values using the EuroQol Group 5-Dimension Self-Report Questionnaire at 90 days post-stroke.
• Performed simulations to compare UW-mRS with dichotomized and ordinal mRS analyses for statistical power.

Main Results:

• Mean utility values for mRS categories 0-6 ranged from 0.95 to 0, with significant individual variation.
• UW-mRS demonstrated higher efficiency than dichotomous mRS (85% vs. 71% power).
• Ordinal mRS analysis showed the highest statistical efficiency (87% power) compared to UW-mRS (85% power).

Conclusions:

• The UW-mRS approach, by averaging utilities, does not account for individual patient variations.
• This lack of individual variation capture may reduce the statistical power of randomized stroke trials.
• Ordinal analysis of the mRS is statistically more efficient than the UW-mRS for detecting treatment effects.