A pilot validation study for the NOX T3(TM) portable monitor for the detection of OSA

The aim of the current pilot study is to compare the diagnostic accuracy of the NOX T3(TM) (T3) portable sleep monitor (PM) to that of simultaneously recorded in-lab polysomnogram (PSG).

A total of 40 participants were recruited following face-to-face evaluation at a sleep disorders clinic. Each participant wore both PSG and PM equipment simultaneously during their in-lab PSG. PSG records were manually scored using the American Academy of Sleep Medicine (AASM) criteria, and PM records were double-scored using the device's autoscore algorithm as well as manual scoring.

The final sample consisted of 32 participants (56% male, 50% black) with a mean ESS, BMI, and apnea-hypopnea index (AHI) of 10.4, 32.8, and 16.3, respectively. Three participants (7.5%) were excluded for poor PM signal quality. Mean AHI derived from the T3's autoscore algorithm was similar to that from manual scoring (19.6 ± 18.9 vs. 18.6 ± 19.1, respectively). Autoscore-derived T3 AHI and PSG-derived AHI were strongly related (r = .93). The T3 (autoscored AHI) demonstrated a high degree of sensitivity for the presence of obstructive sleep apnea syndrome (OSA; 100%) and acceptable specificity for the exclusion of OSA using an AHI cutoff of ≥5 events/h (70%). The unit (autoscored) had a high degree of both sensitivity (92%) and specificity (85%) when the presence of OSA was defined more conservatively (AHI > 15 events/h). For OSA defined as an AHI of ≥5, the T3 (autoscored) correctly identified 88% of positive cases and 100% of negative cases.

In this small, clinic-based sample, the T3 demonstrated very good measurement agreement compared to PSG and a high degree of sensitivity for detecting even mild OSA. False positives appeared to be due to respiratory effort-related arousals (RERAs) being autoscored as obstructive apneas and may be due to inherent discrepancy in flow measurement sensitivity between PSG and portable monitors.