Objectives: This study aimed to evaluate the usefulness of the Berlin questionnaire (BQ) as a screening tool for obstructive sleep apnea (OSA) in a sleep clinic.Methods: We used a retrospective review of 77 subjects with suspected OSA to conduct a secondary analysis of a previously published sleep study. A total of 77 subjects attended and completed overnight, in-laboratory polysomnography. Subjects completed the standard BQ in the evening just before the sleep study.Results: The mean age of 77 subjects was 49.94±15.78 years, of which 37 (48.1%) were male and 42 (63.7%) were white. Forty-six subjects (59.7%) were diagnosed with OSA through polysomnography. In the analysis of each item of the standard BQ, the sensitivity ranged from 4.6% to 92.5%, and the specificity ranged from 13.3% to 85.7%. For item 8, the sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio were 4.6%, 84.9%, 0.3, and 1.1, respectively. The area under the curve values of the standard BQ and after deleting item 8 were 0.634 and 0.751, respectively. When item 8 was deleted and each item on the standard BQ was calculated as one point, the cutoff values representing the highest Yuden index were 3.5 and 4.5.Conclusions: A modified BQ that selects four different questions for each subje...