Section on Stroke Diagnostics and Therapeutics, National Institute of Neurological Disorders and Stroke (NINDS), Bethesda, Md
The modified Rankin Scale (mRS) and Barthel Index (BI) are often used to evaluate long-term outcome in stroke studies.1–3 However, there are several potential problems with their use. An investigator’s knowledge of the clinical data may bias scoring of the scales, and direct patient contact for outcome assessment months after the stroke is not always feasible. Telephone interviews can simplify study design and potentially avoid investigator bias. Telephone interviews have been used prospectively in stroke studies to evaluate clinical outcome, functioning and disability after stroke, cognitive status, stroke-free status, and cognitive function in community outpatients.4,5 Newcommon et al conducted a study to validate assessment of the mRS over the telephone by nonphysician interviewers using a structured interview. They found that inter-rater reliability was excellent between physician observers in the clinic but less so between each of 2 clinical observers and the telephone interviewer (=0.38 [95% CI, 0.21 to 0.55] and =0.3 [95% CI, 0.13 to 0.47]).6 The agreement was higher for patients with Rankin scores at either end of the scale (mRS=0 or 4). The reliability of the commonly used scales to detect the cut-off points in the BI and the mRS when not interviewing the patient face-to-face is unknown.7
The objective of this pilot study was to test the hypothesis that mRS and BI scores obtained over the phone by an experienced research nurse correlate with scores taken during the clinical evaluation. We scored the BI and mRS of 33 consecutive stroke patients who returned for follow-up visit 2 to 3 months after the index stroke. Subsequently, an experienced research nurse blind to all previous clinical and radiological data scored the scales via phone interview. We compared median scores obtained by the 2 scorers with the Wilcoxon Rank test. To evaluate the correlation between in-person and phone scores, we dichotomized the scores using cut-off points commonly used in stroke trials (mRS 1, mRS 2, and BI 95) and calculated unadjusted values. We also used unadjusted values to evaluate the agreement between observers based on tissue plasminogen activator (tPA) treatment status. The mean (SD) time to scoring in person and on the phone was 85 (28) and 150 (58) days, respectively. The median mRS was 1 for in-person scoring and 0 over the phone (P=0.03). The difference may be attributable to the time elapsed between interviews. The median BI score by both scorers was 100. The table details the agreement between observers. When outcomes were dichotomized, there was substantial agreement between the clinical and phone scores for all outcomes regardless of tPA treatment status.
Agreement Between In-Person and Phone Scoring (Unadjusted [95% CI])
Our findings suggest that an experienced blinded rater can reliably score commonly used stroke outcome measures over the phone. This has implications for the design of stroke studies. A central rater may reduce bias and the inter-rater variability and may be preferable in large clinical trials, particularly those that involve multiple institutions. Validation in a larger sample is under way.
References
Mahoney FI, Barthel DW. Functional evaluation: the Barthel index. Md State Med J. 1965; 14: 61–65.
Rankin J. Cerebral vascular accidents in patients over the age of 60. II. Prognosis. Scott Med J. 1957; 2: 200–215.
Bonita R, Beaglehole R. Recovery of motor function after stroke. Stroke. 1988; 19: 1497–1500.
Barber M, Stott DJ. Validity of the Telephone Interview for Cognitive Status (TICS) in post-stroke subjects. Int J Geriatr Psychiatry. 2004; 19: 75–79.
Meschia JF, Brott TG, Chukwudelunzu FE, Hardy J, Brown RD Jr, Meissner I, Hall LJ, Atkinson EJ, O’Brien PC. Verifying the stroke-free phenotype by structured telephone interview. Stroke. 2000; 31: 1076–1080.
Newcommon NJ, Green TL, Haley E, Cooke T, Hill MD. Improving the assessment of outcomes in stroke: use of a structured interview to assign grades on the modified Rankin scale. Stroke. 2003; 34: 377–378.
Young FB, Lees KR, Weir CJ. Strengthening acute stroke trials through optimal use of disability end points. Stroke. 2003; 34: 2676–2680.
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