Occult sleep apnea: the dilemma of negative polysomnography in symptomatic patients

To determine the benefit of repeat polysomnography with/without esophageal pressure (PES) monitoring to diagnose sleep apnea syndrome (SAS) in patients with symptoms of sleep apnea who have had a 'negative', single-night polysomnogram (PSG).

This is a retrospective investigation of 1187 patients seen in our sleep lab from January to December 2001, of which 709 were adults suspected of having sleep apnea. Following a single PSG, 588 patients were diagnosed with sleep apnea and 121 had negative PSGs (an apnea-hypopnea index <5 events per hour). Of the 121 patients, 92 continued to complain of unexplained sleepiness, loud snoring, or apnea, symptoms which were also documented on their initial evaluation (PSG or multiple sleep latency testing). The remaining 29 patients had no further complaints, or another medical cause of their sleepiness was established (i.e. asthma) following the single-night PSG. Of the 92 patients, 28 underwent additional screening with both repeat PSG and PES monitoring within the following 6 months.

With repeat PSG and PES monitoring, 18 of the 28 patients with previous, negative PSGs were diagnosed with sleep apnea. The sensitivity of a single-night PSG fell to 97%, with a false negative rate of 3%. Only 12 of the 28 would have been positive based on polysomnographic criteria alone, without the additional PES monitoring. On the other hand, 10 of the 28 remained negative and further evaluation revealed other, underlying medical problems (i.e. nocturnal asthma) that explained their symptoms.

There is a clear benefit of repeat PSG, with or without PES monitoring, for patients with a prior negative PSG and continued symptoms suspected of having SAS.