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Four questions plus home monitor useful for diagnosing sleep apnea

Clinical Question:
Can a simple clinical model and home monitoring accurately diagnose obstructive sleep apnea?

Bottom Line:
Four simple questions, plus a home oxygen saturation monitor, is an inexpensive and moderately accurate way to diagnose obstructive sleep apnea (OSA). (LOE = 1b)

Reference:
Chai-Coetzer CL, Antic, NA, Rowland LS, et al. A simplified model of screening questionnaire and home monitoring for obstructive sleep apnoea in primary care. Thorax 2011;66(3):213-219.  [PMID:21252389]

Study Design:
Cross-sectional

Funding:
Government

Setting:
Outpatient (primary care)

Synopsis:
Polysomnography is expensive and inconvenient, and may not be easily available to patients in rural or under-resourced settings. The authors of this study set out to develop and validate a simple, practical approach for primary care diagnosis of OSA. They first identified a sample of primary care patients presenting for any reason, but oversampled from patients at high risk for OSA based on their responses to the validated Berlin questionnaire. The overall prevalence of OSA in the final population was 21%. All patients completed a questionnaire and then underwent a full polysomnogram (PSG) in their home, as well as a simplified study using the "ApneaLink" device that only measured oxygen saturation and nasal air flow. The PSG was the reference standard, using an apnea hypopnea index of 30 or higher as the cutoff for an abnormal result. The mean age of participants was 52 years, 50% were women, and the average body mass index was just higher than 30 kg/m2. The first 79 patients were considered the development group and were used to develop the prediction model, while the next 78 patients were called the validation group and were used to evaluate its accuracy. The researchers identified 4 independent predictors of OSA and assigned each one a point value: the patient's snoring has bothered other people (3 points), a waist circumference greater than 102 cm in men or greater than 88 cm in women (3 points), being older than 50 years (2 points), and someone has noticed that the patient stops breathing during sleep (2 points). The total score had 10 points, and a positive screening result was 5 or more points. This clinical rule was 100% sensitive in the development group; the ApneaLink monitor had good accuracy using at least 3% oxygen desaturation as the cutoff for an abnormal result (area under the ROC curve = 0.96). With the goal of minimizing the need for PSG or home monitoring, the researchers proposed a 2-stage diagnostic model. Patients with a score of 5 or higher on the clinical rule would use the home ApneaLink monitor, and those with at least 3% oxygen desaturation would be given the diagnosis of sleep apnea. This approach was tested prospectively in the validation group, and it had excellent negative predictive value (96%) and moderately good positive predictive value (56%). The positive and negative likelihood ratios were also good: LR+ = 4.93 and LR- = 0.15.

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