Variability and Misclassification of Sleep Apnea Severity Based on Multi-Night Testing

Abstract

Background: Portable monitoring is a convenient means for diagnosing sleep apnea. However, data on whether one night of monitoring is sufficiently precise for the diagnosis of sleep apnea are limited.

Research question: The current study sought to determine the variability and misclassification in disease severity over three consecutive nights in a large sample of patients referred for sleep apnea.

Methods: A sample of 10,340 adults referred for sleep apnea testing was assessed. A self-applied type III monitor was used for three consecutive nights. The apnea-hypopnea index (AHI) was determined for each night, and a reference AHI was computed by using data from all 3 nights. Pairwise correlations and the proportion misclassified regarding disease severity were computed for each of the three AHI values against the reference AHI.

Results: Strong correlations were observed between the AHI from each of the 3 nights (r = 0.87-0.89). However, substantial within-patient variability in the AHI and significant misclassification in sleep apnea severity were observed based on any 1 night of monitoring. Approximately 93% of the patients with a normal study on the first night and 87% of those with severe sleep apnea on the first night were correctly classified compared with the reference derived from all three nights. However, approximately 20% of the patients with mild and moderate sleep apnea on the first night were misdiagnosed either as not having sleep apnea or as having mild disease, respectively.

Conclusions: In patients with mild to moderate sleep apnea, one night of portable testing can lead to misclassification of disease severity given the substantial night-to-night variability in the AHI.

Keywords: home sleep apnea test; portable monitoring; sleep apnea.

Figure 1

Within-patient SD of the AHI vs the reference AHI values derived from the 3 nights of home sleep testing. AHI = apnea-hypopnea index.

Figure 2

Pairwise and Bland-Altman plots of the AHI from the three nights of home sleep testing. The dashed lines in the plots on the left represent lines of identity. The dashed lines in the plots on the right represent the limits of agreement (mean bias ± 1.96 SD). See Figure 1 legend for expansion of abbreviation.

Figure 3

Positive predictive values for an AHI < 5 events/h (top panel) and for an AHI > 30 events/h (bottom panel) for average AHI from 1, 2, and 3 nights of observation. See Figure 1 legend for expansion of abbreviation.