Screening for obstructive sleep apnea among hospital outpatients

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) is common in adults. People with OSAS have a higher risk of experiencing traffic accidents and occupational injuries (OIs). We aimed to clarify the diagnostic performance of a three-channel screening device (ApneaLink(TM)) compared with the gold standard of full-night attended polysomnography (PSG) among hospital outpatients not referred for sleep-related symptoms. Furthermore, we aimed to determine whether manual revision of the ApneaLink(TM) autoscore enhanced diagnostic performance. METHODS: We investigated 68 patients with OI and 44 without OI recruited from the University Hospital Basel emergency room, using a cross-sectional study design. Participating patients spent one night at home with ApneaLink(TM) and within 2 weeks slept for one night at the sleep laboratory. We reanalyzed all ApneaLink(TM) data after manual revision. RESULTS: We identified significant correlations between the ApneaLink(TM) apnea-hypopnea index (AHI) autoscore and the AHI derived by PSG (r = 0.525; p <0.001) and between the ApneaLink(TM) oxygen desaturation index (ODI) autoscore and that derived by PSG (r = 0.722; p <0.001). The ApneaLink(TM) autoscore showed a sensitivity and specificity of 82% when comparing AHI ≥5 with the cutoff for AHI and/or ODI ≥15 from PSG. In Bland Altman plots the mean difference between ApneaLink(TM) AHI autoscore and PSG was 2.75 with SD ± 8.80 (β = 0.034), and between ApneaLink(TM) AHI revised score and PSG -1.50 with SD ± 9.28 (β = 0.060). CONCLUSIONS: The ApneaLink(TM) autoscore demonstrated good sensitivity and specificity compared with the gold standard (full-night attended PSG). However, Bland Altman plots revealed substantial fluctuations between PSG and ApneaLink(TM) AHI autoscore respectively manually revised score. This spread for the AHI from a clinical perspective is large, and therefore the results have to be interpreted with caution. Furthermore, our findings suggest that there is no clinical benefit in manually revising the ApneaLinkTM autoscore.