Validity and reliability of a new, short symptom rating scale in patients with persistent atrial fibrillation

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Abstract
Symptoms related to atrial fibrillation and their impact on health-related quality of life (HRQoL) are often evaluated in clinical trials. However, there remains a need for a properly validated instrument. We aimed to develop and validate a short symptoms scale for patients with AF. One hundred and eleven patients with a variety of symptoms related to AF were scheduled for DC cardioversion. The mean age was 67.1 ± 12.1 years, and 80% were men. The patients completed the new symptoms scale, the Toronto Symptoms Check List (SCL) and the generic Short Form 36 (SF-36) the day before the planned DC cardioversion. Compliance was excellent, with only 1 of 666 answers missing. One item, 'limitations in working capability', was deleted because of a low numerical response rate, as many of the patients were retired. The internal consistency reliability of the remaining six items was 0.81 (Cronbach's α). Patients scored highest in the items of 'dyspnoea on exertion', 'limitations in daily life due to AF' and 'fatigue due to AF', with scores of 4.5, 3.3 and 4.5, respectively. There was a good correlation to all relevant SF-36 domains and to the relevant questions of the SCL. The Rasch analyses showed that the items are unidimensional and that they are clearly separated and cover an adequate range. Test-retest reliability was performed in patients who failed DC and was adequate for three of six items, >0.70. The psychometric characteristics of the new short symptoms scale were found to have satisfactory reliability and validity.