Which version of the modified Rankin Scale should we use for stroke trials?

The modified Rankin Scale (mRS) is frequently used as a measure of global disability in stroke trials.^1,2 Its advantages include excellent construct validity and feasibility,² minimal time requirement, and flexibility for either face-to-face or telephone delivery.³ However, disadvantages include low reliability (κ = 0.25)⁴ and that the 7-point scale (0–6, with 6 being death) can miss important aspects of incremental recovery.² Although the mRS was originally developed as an ordinal scale, it has commonly been dichotomized for analysis, either 0–1 vs 2–6, or 0–2 vs 3–6. The clinical research community actively debates the best analytical approach to use in clinical stroke trials. Of note, in practice, the original mRS included both premorbid and postmorbid mRS assessments to allow meaningful comparative clinical interpretation. Although clinical trials often collect premorbid mRS score as a core variable, interpretation as a preclinical assessment has been unclear, until now. Recently, Quinn et al.⁵ conducted an evaluation of the prestroke mRS for its prognostic accuracy and validity as a measure of prestroke disability and reported it as a robust predictor of prognosis.⁵