Preliminary validity and reliability of a Thai Berlin questionnaire in stroke patients

BACKGROUND: Obstructive sleep apnea (OSA) is a major risk factor for stroke. The Berlin Questionnaire (BQ) has been shown to be a valid tool to screen for OSA. The literature has limited data on using the BQ in stroke patients; particularly in Thailand and other developing countries. Here, we aimed to develop a Thai-language Berlin Questionnaire (Thai BQ) and to preliminarily assess construct validity, test-retest reliability and the agreement of the Thai BQ with the Thai Epworth Sleepiness Scale (Thai ESS), another screening tool for OSA. METHODS: A hospital-based cross-sectional study was performed from January to July, 2011. One hundred first-ever stroke patients, including acute and chronic cases, and their caregivers were enrolled. The Thai BQ was developed using the forward-backward translation method. Evaluation of construct validity was done by factor analysis. Internal consistency of the Thai BQ and the Thai ESS were evaluated using Cronbach’s alpha coefficient. Test-retest reliability and the agreement of the Thai BQ and the Thai ESS were evaluated using Cohen’s kappa coefficient. RESULTS: Factor analysis identified 4 main factors: Factor 1–Snoring behaviour; Factor 2–Sleepiness during driving; Factor 3–Daytime fatigue; and Factor 4–Hypertension or obesity. Cronbach’s alpha coefficient was 0.77 (95% confidence interval (CI) = 0.69-0.83) and Cohen’s kappa coefficient was 0.86 (95% CI = 0.74-0.98) in the Thai BQ. Cronbach’s alpha coefficient was 0.59 (95% CI = 0.45-0.70) and the Cohen’s kappa coefficient was 0.81 (95% CI = 0.60-1.00) in the Thai ESS. The agreement between the Thai ESS and the Thai BQ was fair. CONCLUSIONS: The Thai BQ is a valid and reliable tool to screen for OSA in stroke patients. As factor analysis revealed 4 factors in contrast to the 3 factors in the original BQ, further modification of the Thai BQ is required.