Comparison of telephone and face-to-face assessment of the modified Rankin Scale

A structured interview improves the reliability of the modified Rankin Scale (mRS), a commonly used functional outcome scale in stroke trials. Telephone interview is a fast and convenient way to assess the mRS grade, but its validity is unknown. We assessed the validity of a telephone interview in patients who had had an aneurysmal subarachnoid haemorrhage (SAH) by comparing it with a face-to-face assessment.

Eighty-three SAH patients were interviewed twice, once face-to-face and once by telephone, by 2 of 5 observers who used a structured interview to assess the mRS grade. Intermodality agreement was measured using weighted kappa statistics. To check for systematic differences between face-to-face and telephone assessment the Wilcoxon test for matched pairs was used.

Agreement between telephone and face-to-face assessment was perfect in 47 (57%) patients. A difference of 1 level occurred in 31 (37%) patients and this was almost equally distributed over the grades of the mRS. Weighted kappa was 0.71 (95% CI 0.59-0.82). Telephone assessment did not result in a consistently more or less favourable grade than face-to-face assessment (Wilcoxon test for matched pairs, p = 0.33).

Telephone assessment of the mRS with a structured interview has a good agreement with face-to-face assessment and can thus be used reliably in the setting of a clinical trial.