VANCOUVER, B.C. – Recent research on the use of home testing for the diagnosis of obstructive sleep apnea and initiation of therapy suggests that "home testing is here to stay," Dr. Charles W. Atwood Jr. told attendees at the annual meeting of the American College of Chest Physicians.
For more than 30 years, physicians have relied on the traditional polysomnography performed in the sleep laboratory to diagnose sleep apnea, according to Dr. Atwood. But with growing awareness of the condition and its prevalence, the number of people needing testing could overwhelm capacity.
"If you take the millions and millions and millions of people in the United States alone who have sleep apnea and try to feed them through the relatively small funnel of traditional sleep labs, then you are going to have big bottlenecks," he said, adding that such bottlenecks already exist in some areas.
However, home-testing devices must meet certain key requirements before they are ready for widespread use. For example, they have to be simpler than those used in the lab. "Perhaps we can get by with fewer [physiological] signals, but we need to understand what the key signals are," commented Dr. Atwood, a pulmonologist and sleep medicine specialist with the VA Pittsburgh Healthcare System and the University of Pittsburgh Medical Center.
Home testing devices will also need to be accurate, with high sensitivity and specificity, and "there is no single device I would say today that is perfect in both these regards," he noted. Finally, they must be easy to use and durable, given the demands of in-home use.
Roughly 95 studies conducted between 1990 and 2006 evaluated home testing (also called portable monitoring) for the diagnosis of obstructive sleep apnea. Collectively, they had some limitations, such as their single-site nature, small and usually homogeneous populations, and varying degrees of rigor in design.
"And they frequently focused on the highest-risk subjects: These were middle-aged men who were overweight, snored, and were sleepy, so [they were] the very low-hanging fruit for typical sleep apnea," Dr. Atwood said.
These studies showed mixed results when it came to the diagnostic performance of home testing relative to lab testing. "There is no perfect study, at least so far, in this area, but some have come pretty close," he commented.
Three more recent studies suggest that home testing is at least not inferior to lab testing for sleep apnea diagnosis and initiation of continuous positive airway pressure (CPAP) therapy, according to Dr. Atwood.
In the first study, conducted among 68 people with a high likelihood of sleep apnea, the apnea-hypopnea index on CPAP and Sleep Apnea Quality of Life Index scores at 3 months did not differ significantly between a sleep lab approach and an ambulatory approach (Ann. Intern. Med. 2007;146:157-66). The rate of adherence to CPAP was better with the latter.
In the second study, which involved 102 patients with sleep apnea symptoms and no major comorbidities, all of a variety of sleep and quality of life outcomes after 4 weeks of CPAP were similar with a standard lab diagnosis and treatment approach vs. a home approach (Chest 2010;138:257-63).
The third study, the Veterans Sleep Apnea Treatment Trial (VSATT), is the largest study of home testing in North America to date, according to Dr. Atwood, who is one of the principal investigators.
"The VA is ill equipped to manage sleep apnea in a conventional way because we have relatively few numbers of traditional sleep labs, and those sleep labs that do exist tend to be kind of small," he noted. Also, there are geographic disparities, with some veterans having virtually no access to sleep labs.
"Our study differed from basically all of the other studies in the literature in that we had very broad inclusion criteria and very nonrestrictive exclusion criteria," Dr. Atwood noted. For example, patients with comorbidities could participate as long as their condition was stable.
The patients were randomized to lab testing or home testing, followed by initiation of CPAP for those with positive results.
Among the 223 who were started on CPAP, the home and lab groups had similar demographics. The average apnea-hypopnea index was 41 for the former and 45 for the latter. The Functional Outcomes of Sleep Questionnaire (FOSQ) total score was about 15 in each group.
Results showed that the mean adjusted improvement in FOSQ total score between baseline and 3 months was identical in the two groups, at 1.79 points. And within each group, patients had significant improvements in the total score as well as its individual components.