title: High prevalence of undiagnosed obstructive sleep apnoea in the general population and methods for screening for representative controls.
abstract: OBJECTIVE
  Undiagnosed obstructive sleep apnoea (OSA) in the community makes comparisons of OSA subjects with control samples from the general population problematic. This study aims to estimate undiagnosed moderate to severe OSA in a general population sample and to determine the capacity of questions from the Berlin questionnaire (BQ) to identify subjects without diagnosed OSA of this severity.
  
  
  METHODS
  Using a general population sample (n = 793) with no history of OSA, case and control status for moderate-severe OSA was determined by home-based nasal flow and oximetry-derived apnoea-hypopnoea index using a cut-off value of ≥ 15 events/h to define cases. The diagnostic accuracy of the complete BQ and its component questions in identifying cases was assessed by calculating sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios and post-test probabilities.
  
  
  RESULTS
  The age-standardised prevalence estimate of moderate-severe OSA was 9.1 % (12.4 % in men, 5.7 % in women). Sensitivity of the BQ in this population was 54 %, and specificity, 70 %. A combination of questions regarding snoring frequency and hypertension provided maximal post-test probability of OSA and greatest post-screen sample size.
  
  
  CONCLUSIONS
  Undiagnosed OSA is highly prevalent in the Western Australian general population. While the complete BQ is a sub-optimal screening instrument for the general population, snoring frequency or hypertension can be used to screen out moderate-severe OSA from general population samples with limited reduction in sample size. As there are few general population samples available for epidemiological or genetic studies of OSA and its associated phenotypes, these results may usefully inform future case-control studies.
authors.affiliation: Centre for Genetic Epidemiology and Biostatistics, University of Western Australia, 14-16 Parkway, Crawley, Perth, 6009 WA, Australia. lsimpson@meddent.uwa.edu.au
authors.forename: Laila
authors.initials: L
authors.lastname: Simpson
authors.forename: David R
authors.initials: DR
authors.lastname: Hillman
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Cooper
authors.forename: Kim L
authors.initials: KL
authors.lastname: Ward
authors.forename: Michael
authors.initials: M
authors.lastname: Hunter
authors.forename: Stewart
authors.initials: S
authors.lastname: Cullen
authors.forename: Alan
authors.initials: A
authors.lastname: James
authors.forename: Lyle J
authors.initials: LJ
authors.lastname: Palmer
authors.forename: Sutapa
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Peter
authors.initials: P
authors.lastname: Eastwood
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D057210:Delayed Diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000706:statistics & numerical data*; D008875:Middle Aged; D017286:Polysomnography; D011594:Psychometrics / Q000706:statistics & numerical data; D012123:Pulmonary Ventilation / Q000502:physiology; D015203:Reproducibility of Results; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014904:Western Australia