Development and validation of a short measure of health status for individuals with acute myocardial infarction: the myocardial infarction dimensional assessment scale (MIDAS)

The purpose of this study was to develop and validate a disease-specific health status measure for individuals with myocardial infarction (MI). The development of the myocardial infarction dimensional assessment scale (MIDAS) followed three main stages. Stage 1 consisted of in-depth, semi-structured, exploratory interviews conducted on a sample of 31 patients to identify areas of salience and concern to patients with MI. These interviews generated 48 candidate questions. In stage 2 the 48-item questionnaire was used in a postal survey to identify appropriate rephrasing/shortening, to determine acceptability and to help identify sub-scales of the instrument addressing different dimensions of MI. Finally, in stage 3 the construct validity of MIDAS subscales was examined in relation to clinical and other health outcomes. A single centre (district general hospital) in England was used to stages 1 and 3 and a national postal survey was conducted for stage 2. A total of 410 patients were recruited for the national survey (stage 2). Full data were available on 348 (85%) patients. One hundred and fifty-five patients were recruited to test construct validity (stage 3). The MIDAS contains 35 questions measuring seven areas of health status: physical activity, insecurity, emotional reaction, dependency, diet, concerns over medication and side effects. The measure has high face, internal and construct validity and is likely to prove useful in the evaluation of treatment regimes for MI.