The minimum period of polysomnography required to confirm a diagnosis of severe obstructive sleep apnoea

BACKGROUND AND 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.