Development of a health-related quality of life questionnaire for Thai patients with rhinoconjunctivitis.

The objective of this study was to develop a disease-specific questionnaire for patients with rhinoconjunctivitis. All patients were recruited at the Out-Patient Clinic at Siriraj Hospital. Related topics were gathered from several sources, and a list of 63 items was produced. In phase I, the first version of the questionnaire was completed by 363 patients. Forty-eight items were identified by clinical impact analysis during the item removal process, two more questions were then added, giving a total of 50. Two hundred and forty-three patients completed the second version questionnaire in phase II. The average time taken to complete the questionnaire was 6.38 minutes. The item removal process in phase II was achieved by a multi-step process. There were 36 items in the third version questionnaire which consisted of six dimensions and two independent items as follows: symptoms (17 items), physical functioning (3 items), role limitations (3 items), sleep (3 items), social functioning (3 items), emotions (5 items), general health (1 item), and absenteeism (1 item). The scores of each item ranged from 1 to 5; a lower score indicating a better quality of life. Data from the selected 36 items was extracted to test the validity and reliability of the final version. The floor and ceiling effects of the scores for each dimension were low. Multitrait multi-item analysis was conducted to examine construct validity. The scaling success of convergent and divergent validity was 100% and 94%, respectively. Internal consistency determined by Cronbach's alpha coefficient, was satisfactory (0.79-0.87). The study indicates that the questionnaire is suitable for use in clinical settings. While the test results are encouraging, further work needs to be done on the test-retest reliability and on responsiveness.