title: Validation of a portable recording device (ApneaLink) for identifying patients with suspected obstructive sleep apnoea syndrome.
abstract: BACKGROUND
  Polysomnography (PSG) is currently the standard diagnostic procedure for sleep apnoea. This study evaluates the diagnostic accuracy of a portable recording device, ApneaLink (AL; ResMed, Poway, CA, USA) for detection of sleep apnoea in comparisons against PSG.
  
  
  METHODS
  The AL device is a three-channel screening tool that measures airflow through a nasal pressure transducer, oximetry and pulse, providing an apnoea-hypopnoea index (AHI) based on recording time. Nocturnal PSG (Alice 4; Healthdyne, Atlanta, GA, USA), with airflow measured by a nasal pressure transducer (ProTech PTAF2; ProTech, Woodinville, WA, USA) and AL recordings were carried out simultaneously in consecutive patients with suspected obstructive sleep apnoea syndrome (OSAS). The PSG recordings were analysed manually by a blinded investigator. The oxygen desaturation index of AL was also compared against the AHI based on PSG.
  
  
  RESULTS
  Fifty consecutive subjects with symptoms of OSAS were recruited with mean age of 50 years and body mass index of 27.9 kg/m2. The AHI obtained by the AL device correlated closely to that obtained by PSG (Pearson correlation, r= 0.978, P < 0.001), whereas the correlation between PSG AHI and oxygen desaturation index by AL was also strong (r= 0.895, P < 0.001). Comparison of AHI based on the AL against the PSG demonstrated high sensitivity and specificity at AHI > or =10/h (sensitivity 0.977 and specificity 1.0) and at AHI > or =20/h (sensitivity 0.969 and specificity 1.0).
  
  
  CONCLUSIONS
  The AL portable monitoring device is highly sensitive and specific in quantifying the apnoea-hypopnoea index when compared against hospital based polysomnography in patients with suspected OSAS. The simple device may be useful for screening and diagnostic purpose when access to PSG is limited.
authors.affiliation: Department of Medicine and Therapeutics, Division of Respiratory Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China.
authors.forename: S S S
authors.initials: SS
authors.lastname: Ng
authors.forename: T-O
authors.initials: TO
authors.lastname: Chan
authors.forename: K-W
authors.initials: KW
authors.lastname: To
authors.forename: J
authors.initials: J
authors.lastname: Ngai
authors.forename: A
authors.initials: A
authors.lastname: Tung
authors.forename: F W S
authors.initials: FW
authors.lastname: Ko
authors.forename: D S C
authors.initials: DS
authors.lastname: Hui
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation* / Q000379:methods / Q000592:standards*; D017286:Polysomnography / Q000295:instrumentation* / Q000379:methods / Q000592:standards*; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology