With millions of people affected by undiagnosed obstructive sleep apnea in the U.S. alone, in-lab polysomnography for everyone is simply not feasible. The Institute of Medicine acknowledged as much in this 2006 report, calling for the development and testing of new portable technologies to meet the need.
In-home apnea testing, or simply prescribing auto-titrating devices to high-risk people, have been investigated as potential solutions to this public health problem. This website reported a recent VA study in which home sleep studies were usually sufficient. A primary care-based approach to home testing was used with success in this 2011 UK study.
Sleep specialists counter that home testing today simply isn’t accurate enough, and isn’t ready for wide deployment by untrained generalist physicians. In a randomized trial, Masa et al provide some credence to that concern.
In a cross-over study at 8 centers, they randomized 348 patients considered at intermediate- or high-risk for sleep apnea to undergo sleep apnea testing both unattended at home (“polygraphy”) and attended in the hospital (polysomnography), in random sequence with no more than 3 nights separating the 2 studies in each patient.
The gold standard was the final therapeutic decision at the end of the study, which was based on polysomnography. (They didn’t just compare the results of the two tests, but rather the “therapeutic decision” made after patients’ data were presented to physicians per protocol, in random order and from both modalities [PSG and polygraphy]. Each patient got a therapeutic decision [CPAP or no CPAP] from each testing modality, and those decisions were the results compared.
- When AHI was 30 or greater on home polygraphy (41% of the sample), clinical decisions using polygraphy identified 94% of the people ultimately determined to have OSA (sensitivity of 94%). However, this was at the cost of a 56% false positive rate (specficity 44%).
- When AHI was 5 to 30, home polygraphy performed poorly. Decisions based on polygraphy had sensitivity of only 52%, and specificity 72%, for predicting the final clinical decision.
- Its overall performance was 73% sensitivity and 77% specificity.
Clearly, the trick here is using home polygraphy in the correct (high risk) patients. To help identify them, authors used logistic regression to identify risk factors that increased the likelihood someone would have AHI >= 30 on home polygraphy:
- Obesity (BMI > 30): odds ratio 4.4
- Age >= 55: odds ratio 2.7
- Hypertension or witnessed apneas: odds ratio ~2 each.
- Snoring and nocturia had only odds ratios of ~1.5.
These were univariate so it’s unclear whether they would be additive if present in combination. Nevertheless, to me, home polygraphy looks like it should be fine to use in obese patients over 55 with hypertension and snoring. That’s a lot of people.
Masa JF et al. Therapeutic Decision-making for Sleep Apnea and Hypopnea Syndrome Using Home Respiratory Polygraphy: A Large Multicentric Study. Am J Respir Crit Care Med 2011;184:964-971.