Tuesday, January 31, 2017

Obstructive sleep apnea: screening and home testing news

- Kenny Lin, MD, MPH

According to a recent article in AFP, obstructive sleep apnea (OSA) is present in 2 to 14 percent of the general adult population, with a higher prevalence in older and obese persons. Most people are unaware of their diagnoses, either because they do not recognize symptoms or do not report them to physicians. Since it is hard to make an asymptomatic person feel better, is there any good reason to screen for OSA in asymptomatic adults? Screening advocates suggest that treating patients with moderate to severe OSA with continuous positive airway pressure (CPAP) reduces hypoxic episodes that could trigger cardiovascular events in patients with known vascular disease. A POEM in the January 15th issue summarized a randomized trial that seemed to refute this hypothesis. After almost 4 years of follow-up, the group that received CPAP reported slightly less daytime sleepiness, but had the same frequency of cardiovascular events as the control group.

The U.S. Preventive Services Task Force (USPSTF) considered this study and others in issuing a new recommendation statement on January 24th that concluded "the current evidence is insufficient to assess the balance of benefits and harms of screening for OSA in asymptomatic adults." The USPSTF found inadequate evidence that validated questionnaires (such as STOP-BANG) accurately identify who will benefit from polysomnography (PSG) in asymptomatic populations (as opposed to those with suspected OSA). The Task Force also could not determine if CPAP or mandibular advancement devices improve health outcomes (mortality, cognitive impairment, motor vehicle crashes, and cardiovascular or cerebrovascular events) other than sleep-related quality of life.

Although an insufficient evidence statement is not necessarily a recommendation to not screen, Drs. Sachin Pendharkar and Fiona Clement argued in an editorial in JAMA Internal Medicine that the costs of screening for OSA (not considered by the Task Force) warrant clinicians doing just that. Based on the sensitivity and specificity of one widely used screening tool, and an OSA prevalence of 26% in the Medicare population, the authors estimate that $21 billion would be wasted on negative PSG tests, or $4.4 billion if less expensive home-based sleep studies were used instead.

On a related note, the comparative accuracy of home-based tests versus laboratory PSG in diagnosing OSA has been an actively studied topic. A 2014 practice guideline from the American College of Physicians recommended that portable sleep monitors (limited-channel sleep studies) only be used to diagnose OSA when PSG was not available. However, a randomized non-inferiority trial published last week in Annals of Internal Medicine found that patient outcomes after limited-channel studies were similar to those after PSG. This finding may be a blow to the for-profit sleep testing industry, but it is undoubtedly good news for our patients.

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