Obstructive sleep apnea (OSA) is a common but usually under-diagnosed sleep disorder. Objective diagnosis is based on polysomnography, which is an expensive test. We assessed the reliability and diagnostic accuracy of the Berlin questionnaire (BQ) in diagnosis of OSA in Iranian sleep clinic patients.
A cross-sectional linguistic validation study was conducted on consecutive Iranian patients with Persian language attending one sleep clinic in Isfahan (Iran) were studied. Patients completed the Persian BQ (contains 10 questions in 3 categories), developed by forward-backward translation method. The patients underwent an overnight polysomnographic study at the clinic. Apneas/hypopnea index of >5/Hour was considered for diagnosis of OSA.
One hundred and fifty seven patients (55.4% male, mean age = 52.3 ± 13.6 years) were evaluated. Sleep study confirmed OSA diagnosis in 91.7% of the studied patients. The reliability analysis of the BQ categories showed alpha Cronbach's as 0.70 and 0.50 for category 1 and category 2, respectively. BQ categories 1-3 were positive respectively in 88.5%, 67.5%, and 66.9% of the patients. The BQ and sleep study were in agreement for 82.1% of the cases. The sensitivity, specificity, positive and negative predictive values, and positive, and negative likelihood ratio of the BQ were calculated as 84.0%, 61.5%, 96.0%, 25.8%, 2.18%, and 0.26% respectively.
BQ is useful as a screening test for diagnosing OSA in Iranian patients with sleep complaints; however, the test cannot be used for rolling out the OSA. Further studies on editing, modifying, and applying the BQ in a larger sample of patients are warranted in our society.