Objective To estimate prevalence of OSA among at risk adult patients in primary care setting. To test the correlation and agreement between overnight pulse oximetry and polysomnography (PSG). To test the OSA screening performance of overnight pulse oximetry.

Design and Setting Prospective case series involving adult Chinese patients with risk factors for OSA at a primary care clinic of Hong Kong.

Methods The prevalence and severity of OSA were established based on overnight pulse oximetry derived oxygen desaturation index (ODI). Screening performance of overnight pulse oximetry was compared directly with gold standard diagnostic test PSG.

Results Three hundred and five male and 229 female patients were recruited. Snoring (48.3%) was the top presenting symptom. Three hundred and twenty five patients (60.9%) were screened positive to have OSA. One hundred and nine patients had performed PSG, the ODI_4 and apnoea-hypopnea index (AHI) had Pearson correlation coefficient 0.71 (P<0.001). Bland and Altman plot showed good agreement. Using designation criteria of ODI_4≥5 events/hr, the sensitivity and specificity for OSA diagnosis are 94.4% and 78.9% respectively.

Conclusion The prevalence of OSA is 60.9% among adult primary care population who are at risk for OSA. Overnight pulse oximetry shows good performance as a screening tool for the screening of OSA.