Validity of a structured interview for the Modified Rankin Scale: Comparison with other stroke assessment scales
Background & aims: We have recently developed a structured interview for the Modified Rankin Scale (MRS-SI) to improve the inter-rater reliability of this measure of outcome. The purpose of the current study was to investigate the relationship between the MRS-SI and other measures commonly used to assess functional state after stroke. Methods: 119 patients (60 males) were recruited to the study 3 to 24 months after stroke. The median age of patients was 67, and the median interval since stroke was 13 months. Patients were assessed on the Modified Rankin Scale using the structured interview. In addition patients were assessed on the same occasion using the Scandinavian Stroke Scale, the National Institutes of Health Stroke Scales, the Barthel Index, the extended Glasgow Outcome Scale (GOSE) and the Short Form 36 (SF-36). Results: Spearman correlations were computed between ratings on the MRS-SI and other assessments. The MRS-SI was most strongly related to the GOSE. There were also strong correlations with the Barthel Index, the Scandinavian Stroke Scale, and the National Institutes of Health Stroke Scales. However, there was evidence of substantial ceiling effects on all three of these assessments. The MRS-SI correlated significantly with individual subscales of the SF-36, and was particularly strongly related to Physical Function and Social Functioning. However, not all stroke patients were able to complete the SF-36. Conclusions: Systematic relationships observed between the MRS-SI and other established measurement are evidence of the validity of the structured interview. The stroke scales and the Barthel Index discriminate the more disabled groups (Rankin 3 to 5), but are insensitive to functional differences among less severely disabled patients (Rankin 0 to 2). Self-report measures such as the SF-36 indicate differences in health outcome in the less severely disabled groups, but not all stroke patients are able to complete this assessment. A particular strength of the Modified Rankin Scale is the ability to chart the complete spectrum of disability and handicap after stroke.