Underestimation of Sleep Apnea With Home Sleep Apnea Testing Compared to In-Laboratory Sleep Testing

Journal of Clinical Sleep Medicine, Vol. 13, No. 4, 2017 Home sleep apnea testing (HSAT) has made it easier to assess sleep apnea because of its widespread availability and reduced cost compared to in-laboratory polysomnography (PSG). However, the biggest limitation of HSAT is its inability to document sleep stages, which potentially alters the value of the apnea-hypopnea index (AHI) during the sleep study. This occurs largely because HSAT measures total recording time (TRT) rather than total sleep time (TST). Because HSAT measures a patient’s sleep differently than PSG, the American Academy of Sleep Medicine (AASM) prefers to use the term respiratory event index (REI) rather than AHI when patients undergo HSAT. When patients with high pretest probability undergo HSAT, it has been shown to have high sensitivity and specificity for detecting obstructive sleep apnea (OSA),1 but it has been noted in previous studies that HSAT might underestimate overall severity of sleep apnea because of the measurement of TRT and not the TST.2,3 One HSAT device may be the exception—the Apnea Risk Evaluation System—because it utilizes limited frontal electroencephalographic (EEG) channels. The underestimation of sleep apnea severity might pose a significant issue for a clinician because successful management of OSA relies on the accurate measurement of the severity of the patient’s sleep apnea.4 Furthermore, long-term complications of sleep apnea are directly correlated with the severity of sleep apnea.5–8 In this issue of Journal of Clinical Sleep Medicine, Bianchi and Goparaju performed a retrospective analysis comparing TRT to TST in assessing the severity of sleep apnea, and how this would affect the outcome of severity of sleep apnea in a tertiary sleep center population.9 They analyzed a population of 833 who underwent PSG at their center irrespective of etiology for a duration of 2 years. There were 394 subjects with AHI < 5 and 444 with AHI > 5. They re-scored the AHI based on total time in bed in both groups representing TRT as would be measured by HSAT. Both the cohort groups were similar especially with respect to TST and TRT, which was the important part of this study. Reclassification was done only for the group with OSA and it resulted in a classification of one grade less severe in 26.4% of the patients. Further, it was noted that age was significantly correlated with the difference between the initial AHI and recalculated AHI. COMMENTARY