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(Stroke. 2007;38:e145.)
© 2007 American Heart Association, Inc.

Letters to the Editor

Response to Letter by Quinn et al

Health Economics Research and Quality of Life Evaluation Services, Abt Associates, Inc, Lexington, Mass, USA

Charles A. Marotta, MD, PhD

Department of Psychiatry and Human Behavior, Brown University School of Medicine, Providence, RI, USA

Response

We appreciate the comments by Dr Quinn et al concerning our report on the validity and reliability of the modified Rankin Scale (mRS).¹ We agree with the authors in advocating caution in interpreting reliability results for the mRS, given the small number of tests that have been conducted and the limitations of traditional reliability testing. We also agree on emphasizing the importance of accurately classifying clinical end points for randomized clinical trials. This issue is especially relevant to the mRS because it is comprised of a small number of categories for which misclassification can have a substantial impact on statistical power.

Reliability is a complex concept that attempts to ascertain the degree to which an assessment or classification is affected by nonrandom sources of error on the part of raters.² As the authors point out, multiple sources of error variance (eg, nationality, training of the rater) may contribute to misclassification of health levels. Unfortunately, commonly applied tests of reliability may aggregate those sources into single statistics which do not permit a detailed understanding of the performance of an instrument. The feasibility of using more comprehensive tests, such as Rasch analysis or generalizability theory, is unclear in the absence of uniformly applied structured interviews (comprised of items posed to the patient/caregiver). To this point, video training is a more efficient and practical approach to improving mRS reliability.

References

1. Banks J, Marotta CA. Outcomes validity and reliability of the modified Rankin scale: implications for stroke clinical trials. A literature review and synthesis. Stroke. 2007; 38: 1091–1096.[Abstract/Free Full Text]

2. McDowell I, Newell C. Measuring Health: A Guide to Rating Scales and Questionnaires (2^nd edition). New York: Oxford University Press; 1996.

This Article Extract Full Text (PDF) All Versions of this Article: 38/11/e145    most recent STROKEAHA.107.492611v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Banks, J. L. Articles by Marotta, C. A. Search for Related Content PubMed Articles by Banks, J. L. Articles by Marotta, C. A.