A Comprehensive Evaluation of a Two-Channel Portable Monitor to "Rule in" Obstructive Sleep Apnea

Abstract

Study objectives: We hypothesized that a dual-channel portable monitor (PM) device could accurately identify patients who have a high pretest probability of obstructive sleep apnea (OSA), and we evaluated factors that may contribute to variability between PM and polysomnography (PSG) results.

Methods: Consecutive clinic patients (N = 104) with possible OSA completed a home PM study, a PM study simultaneous with laboratory PSG, and a second home PM study. Uniform data analysis methods were applied to both PM and PSG data. Primary outcomes of interest were the positive likelihood ratio (LR+) and sensitivity of the PM device to "rule-in" OSA, defined as an apnea-hypopnea index (AHI) ≥ 5 events/h on PSG. Effects of different test environment and study nights, and order of study and analysis methods (manual compared to automated) on PM diagnostic accuracy were assessed.

Results: The PM has adequate LR+ (4.8), sensitivity (80%), and specificity (83%) for detecting OSA in the unattended home setting when benchmarked against laboratory PSG, with better LR+ (> 5) and specificity (100%) and unchanged sensitivity (80%) in the simultaneous laboratory comparison. There were no significant night-night (all p > 0.10) or study order effects (home or laboratory first, p = 0.08) on AHI measures. Manual PM data review improved case finding accuracy, although this was not statistically significant (all p > 0.07). Misclassification was more frequent where OSA was mild.

Conclusions: Overall performance of the PM device is consistent with current recommended criteria for an "acceptable" device to confidently "rule-in" OSA (AHI ≥ 5 events/h) in a high pretest probability clinic population. Our data support the utility of simple two-channel diagnostic devices to confirm the diagnosis of OSA in the home environment.

Commentary: A commentary on this article appears in this issue on page 411.

Keywords: obstructive sleep apnea; portable monitor; positive likelihood ratio; rule-in; sensitivity; type 4; validation.

Figure 1. Recruitment flow diagram.

*Detail of ineligible subjects given in text. ^#Detail of incomplete data given in text.

Figure 2. Identity and Bland-Altman plots comparing AHI for in-lab PSG with AHI for PM studies, (N = 104, composed of all data from P2 and P3 nights (i.e., Group 1 and Group 2 combined).

(A) Simultaneous recordings (same night and environment, different equipment). (B) Compares PM studies done in-lab and at home (different night and environment, same equipment). (C) Compares in-lab PSG with home PM study (different night, environment and equipment).

Figure 3. Comparisons of AHI for PM before PSG (P1), PM simultaneous with PSG (P2) and PM after PSG (P3) for Group 1 subjects (N = 52).

(A) P1 versus P2 (r = 0.80, p = 0.14). (B) P3 versus P2 (r = 0.87, p = 0.63). (C) P1 versus P3, (r = 0.84, p = 0.26).