Study objectives: To evaluate the validity of the Apnea Risk Evaluation System (ARES) Unicorder, a self-applied, limited-channel portable monitoring device for the evaluation of sleep disordered breathing (SDB).
Design: Prospective study with blinded analysis.
Setting: Sleep disorder center, academic institution.
Participants: Eighty patients with suspected obstructive sleep apnea hypopnea syndrome (OSAHS) and 22 volunteers.
Measurements and results: Subjects used the ARES Unicorder at home for 2 nights using only written instructions. Within 2 weeks, they returned to the laboratory for full nocturnal polysomnography (NPSG) with simultaneous monitoring with the Unicorder. NPSGs were scored manually to obtain an apnea-hypopnea index based on Medicare guidelines (AHI4%) and a respiratory disturbance index (RDI). ARES studies were autoscored and reviewed to obtain indices based on equivalent definitions i.e., AHI4%(ARES) and apnea hypopnea (events with 1% desaturation) index (AHI1%(ARES)). Indices from the NPSG were compared to the in-lab ARES and in-home ARES indices using mean differences and the intraclass correlations (ICC). For the in-lab comparison, there was high concordance between AHI4%(NPSG) and AHI4%(ARES) (ICC = 0. 96, mean difference = 0.5/hour) and RDI(NPSG ) and AHI1%(ARES) (ICC =0.93, mean difference = 3.2/hour). For NPSG versus In-Home ARES comparison, there was good concordance between AHI4%(NPSG) and AHI4%(ARES) (ICC = 0.8, mean difference = 4.1/ hour) and RDI(NPSG) and AHI1%(ARES) (ICC = 0.8 mean difference = 8.6/hour). The diagnostic sensitivity of in-lab ARES for diagnosing SDB using an RDI cut-off of 15 per hour was 95% and specificity was 94%, with a positive likelihood ratio (LR+) =17.04, and negative likelihood ratio (LR-) = 0.06. For in-home ARES data the sensitivity was 85% and specificity 91% (LR+ = 9.34, LR- = 0.17). There was good agreement between the manually scored NPSG SDB indices and the autoscoring ARES algorithm.
Conclusions: ARES Unicorder provides acceptably accurate estimates of SDB indices compared to conventional laboratory NPSG for both the simultaneous and in-home ARES data. The high sensitivity, specificity, and positive and negative likelihood ratios obtained in the group we studied supports the utility of an ambulatory limited-monitoring approach not only for diagnosing sleep disordered breathing but also to rule out SDB in suitably selected groups.