Development and validation of a physical activity questionnaire for patients following cardiac surgery.

Everyone was treated at one hospital in northeast Thailand, and the items reflect that setting (walking on rough paths and fields, agricultural work, using a grass trimmer or mower, driving a light truck), so some questions may not fit patients elsewhere. The questionnaire was never compared with cardiopulmonary exercise testing, which the authors themselves call the gold standard for exercise capacity; it was checked only against a six-minute walk test and two other questionnaires. It covers only the first three months after surgery and says nothing about whether scores change as patients recover or respond to rehabilitation. The walk test used a 15-metre track instead of the 30-metre track recommended by the American Thoracic Society. Patients who could not complete a six-minute walk test, or who had hearing, vision or intellectual problems, were excluded, so the questionnaire has not been tested in the patients who are hardest to assess. The distance estimated from a patient's score agreed only moderately with the distance they actually walked, so the equation should not be read as a measured walk distance. The study is a single snapshot: nobody was followed over time and there is no comparison group, so it cannot show that the questionnaire detects change.

Supported by a grant from the Queen Sirikit Heart Center of the Northeast, Faculty of Medicine, Khon Kaen University, Thailand (grant number 65001). The authors declared that financial support was received for this work and/or its publication and state no other competing interests.

Do not use this questionnaire in place of exercise testing. It was checked against a six-minute walk test and two other questionnaires, never against the full exercise test the authors call the gold standard, and the walking distance it estimates from a patient's score agreed only moderately with the distance patients actually walked.