title: The minimum period of polysomnography required to confirm a diagnosis of severe obstructive sleep apnoea.
abstract: OBJECTIVE
  To combine the diagnosis of OSA with titration of positive airway pressure (PAP), current guidelines recommend that split-night polysomnography (PSG) be performed if an AHI of ≥40/h is recorded over 2h. However, the diagnostic validity of partial-night PSG is uncertain. This study aimed to test the validity of partial-night PSG and to determine the optimum AHI cut-off points.
  
  
  METHODS
  Patients who visited the sleep centre at a tertiary medical centre between January and December 2008, for symptoms related to sleep disorders (sleepiness, snoring, sleep disturbance), and who completed full-night PSG, were evaluated for this study. Full-night PSG data were processed to obtain partial-night PSG data, from which AHI were computed as a reference for diagnosing severe OSA. Full-night and partial-night PSG data obtained over different recording times (expressed as x-h PSG, where xONL001831140 =1-6) were compared using receiver operating characteristic (ROC) curve analysis. The diagnostic validity of 2-h PSG with different AHI cut-off points (25/h to 45/h) was also calculated.
  
  
  RESULTS
  Data from 198 PSG recordings was processed. For 2-h PSG, an AHI cut-off point of 30/h gave the highest accuracy of 90.9%. Comparing areas under the ROC curves (AUC), 2-h PSG (AUC=0.97) was as good as 2.5-h PSG (AUC=0.977, P=0.057) and 3-h PSG (AUC=0.978, P=0.125), but was better than 1.5-h PSG (AUC=0.955, P=0.016).
  
  
  CONCLUSIONS
  Partial-night PSG is effective for diagnosing severe OSA. If there is an unabridged PSG recording indicating an AHI of ≥30/h for 2h, severe OSA can be diagnosed and PAP titration initiated.
authors.affiliation: Chest Department, Taipei Veterans General Hospital, Taipei Institute of Clinical Medicine Faculty of Medicine, School of Medicine Institute of Emergency and Critical Care Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Kun-Ta
authors.initials: KT
authors.lastname: Chou
authors.forename: Yu-Tien
authors.initials: YT
authors.lastname: Chang
authors.forename: Yuh-Min
authors.initials: YM
authors.lastname: Chen
authors.forename: Kang-Cheng
authors.initials: KC
authors.lastname: Su
authors.forename: Diang-Wang
authors.initials: DW
authors.lastname: Perng
authors.forename: Shi-Chuan
authors.initials: SC
authors.lastname: Chang
authors.forename: Guang-Ming
authors.initials: GM
authors.lastname: Shiao
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011175:Positive-Pressure Respiration; D011237:Predictive Value of Tests; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D013624:Taiwan / Q000453:epidemiology; D013997:Time Factors