Background and purpose: The modified Rankin Scale (mRS) is the most common outcome measure in large randomized controlled trials in stroke. We tested 2 postal mRS questionnaires and a telephone questionnaire to determine completion rates and intermodality agreement.
Methods: We sent postal questionnaires containing 2 versions of the mRS to surviving stroke patients. One version, tick box, involved the patient/proxy ticking 1 of the 5 descriptions equating to mRS scores; the other, the simplified modified Rankin questionnaire (smRSq), included 5 questions with yes/no responses from which the mRS is derived. We performed a semistructured telephone interview to consenting respondents, blinded to postal responses, to assign an mRS. We compared the mRS obtained by these different methods.
Results: We sent questionnaires to 343 of 356 surviving patients (96%) and received 225 responses (66%). The mRS could not be derived in 27 respondents (12%) and 10 respondents (4%) on the tick box and smRSq, respectively (difference in proportion, 8% [95% CI, 3-13]. One hundred three of 190 respondents (54%) to the postal questionnaire agreed on the tick box versus smRSq version (κ=0.44 [0.38, 0.50]). Agreements between the tick box versus telephone and smRSq versus telephone were 57% (ie, 87/152, κ=0.47 [0.40, 0.55], and 64% (ie, 104/161, κ=0.55 [0.47, 0.62], respectively.
Conclusions: In large studies where face-to-face assessment of mRS is impractical, a postal smRSq with telephone follow-up to nonresponders will achieve higher levels of follow-up than will the tick box version and also good levels of intermodality agreement with least risk of bias.