Research Article: Screening for obstructive sleep apnea among hospital outpatients

Date Published: May 30, 2018

Publisher: Public Library of Science

Author(s): Michel Hug, Katrin Uehli, Stig Solbach, Stefanie Brighenti-Zogg, Selina Dürr, Sabrina Maier, Jörg Daniel Leuppi, David Miedinger, Thomas Penzel.


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 (ApneaLinkTM) 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 ApneaLinkTM autoscore enhanced diagnostic performance.

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 ApneaLinkTM and within 2 weeks slept for one night at the sleep laboratory. We reanalyzed all ApneaLinkTM data after manual revision.

We identified significant correlations between the ApneaLinkTM apnea-hypopnea index (AHI) autoscore and the AHI derived by PSG (r = 0.525; p <0.001) and between the ApneaLinkTM oxygen desaturation index (ODI) autoscore and that derived by PSG (r = 0.722; p <0.001). The ApneaLinkTM 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 ApneaLinkTM AHI autoscore and PSG was 2.75 with SD ± 8.80 (β = 0.034), and between ApneaLinkTM AHI revised score and PSG -1.50 with SD ± 9.28 (β = 0.060). The ApneaLinkTM 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 ApneaLinkTM 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.

Partial Text

Obstructive sleep apnea syndrome (OSAS) is characterized by repetitive episodes of upper airway obstruction during sleep, which is associated with intermittent hypoxemia, increased work in breathing, and awakening [1]. In general, OSAS is caused by anatomical and/or functional instability of the upper airway, potentially leading to upper airway collapse. Risk factors contributing to OSAS are pre-existing snoring (years of snoring can lead to neurodegenerative damage from vibration trauma and foster an obstruction of the muscular tube) [2] or increasing tissue pressure (e.g. due to adiposity). Studies have demonstrated that elevated body mass index (BMI) can accelerate the development of OSAS or the severity of apnea over time [3]. Snoring may be the earliest nocturnal symptom of OSAS [4]. OSAS is common with a prevalence of at least 4% among the middle-aged male Caucasian population [5,6].

Written informed consent regarding the procedures and for the medical data to be used was obtained from all patients according to the guidelines of the local Ethics Regulation Committee of Basel named Ethikkommission beider Basel (EKBB). Due to a regional expansion in 2015 they changed the name from EKBB to Ethikkommission Nordwest- und Zentralschweiz (EKNZ). The review board of the commission approved this protocol in accordance with the amended Declaration of Helsinki (reference number: 37/09).

In total 160 patients agreed to participate in this study; 112 patients (70%) underwent clinical examination and completed ApneaLinkTM and PSG investigations.

In this cross-sectional study, we investigated the potential of a portable multichannel screening device (ApneaLinkTM) in diagnosing OSAS among hospital outpatients not referred for sleep apnea investigation. ApneaLinkTM results were compared with the gold standard (full-night attended PSG). Furthermore, we evaluated if manual revision of ApneaLinkTM data contributed additional benefit in terms of diagnostic performance.

Our results show that ApneaLinkTM may be used as a clinical screening device for OSAS in patients with an OI. However, given the low number of study participants with OSAS in our study and the AASM recommendation for the use of HSAT only in patients with a high pre-test probability, we do not suggest that HSAT can replace full-night attended PSG in every case. Nevertheless, when compared with data obtained in the sleep laboratory, ApneaLinkTM (autoscore and after manual revision) demonstrated good sensitivity and specificity (82%) when using a AHI threshold ≥5 to detect moderate-to-severe OSAS (AHI and/or ODI ≥15) as derived by full-night attended PSG.This emphasizes the capacity of ApneaLinkTM to recognize OSAS. However, the accuracy of the ApneaLink device remains questionable due to the high misclassification rate compared to the PSG and the large spread in the Bland Altman plots.