Diagnostic accuracy of oximetry for obstructive sleep apnea: a study on older adults in a home setting

Abstract

Objectives: Owing to the fact that obstructive sleep apnea (OSA) is an underreported disease, the strategy used for the diagnosis of OSA has been extensively dissected to devise a simplified process that can be accessed by the public health services. Polysomnography (PSG) type I, the gold standard for the diagnosis of OSA, is expensive and difficult to access by low-income populations. In this study, we aimed to verify the accuracy of the oxyhemoglobin desaturation index (ODI) in comparison to the apnea-hypopnea index (AHI) using a portable monitor.

Methods: We evaluated 94 type III PSG home test results of 65 elderly patients (69.21±6.94 years old), along with information, such as the body mass index (BMI) and sex, using data obtained from a clinical trial database.

Results: A significant linear positive correlation (r=0.93, p<0.05) was observed between ODI and AHI, without any interference from sex, BMI, and positional component. The sensitivity of ODI compared to that of AHI increased with an increase in the severity of OSA, while the specificity of ODI in comparison to that of AHI was high for all degrees of severity. The accuracy of ODI was 80.7% for distinguishing between patients with mild and moderate apnea and 84.4% for distinguishing between patients with moderate and severe apnea.

Conclusion: The ODI values obtained in uncontrolled conditions exhibited high sensitivity for identifying severe apnea compared to the AHI values, and correctly identified the severity of OSA in more than 80% of the cases. Thus, oximetry is promising strategy for diagnosing OSA.

Figure 1. Correlation between the oxyhemoglobin desaturation index (ODI) and the apnea-hypopnea index (AHI) in the entire sample (a). Bland-Altman plot showing the comparison between AHI and ODI with confidence interval of 95% (b).

Figure 2. ROC curves expressing the ability of ODI to distinguish between patients with mild and moderate apnea (curve 1 - blue), between patients with moderate and severe apnea (curve 2 - green), and between patients with mild or no apnea and patients with moderate and severe apnea (AHI>15 cut-off, curve 3 - red). ROC: receiver operating characteristics; AUC: area under the curve; AHI: apnea-hypopnea index; ODI: oxyhemoglobin desaturation index.