NAPLES, Fla.—Sleep studies to detect obstructive sleep apnea can be performed in the patient’s home—although the convenience and lower costs for performing the tests outside the laboratory are offset by a loss of accuracy.
Explore this issue:April 2006
“The lower cost of home sleep studies makes them a viable screening tool for patients with suspected obstructive sleep apnea,” said Mark Ghegan, MD, a researcher in the Department of Otolaryngology–Head and Neck Surgery at the Medical University of South Carolina in Charleston, in a presentation here at the meeting of the Southern Section of the Triological Society.
Dr. Ghegan, however, did note that laboratory polysomnography sleep studies remain the gold standard in the diagnosis of major sleep disorders.
A Widespread Problem
“The problem of obstructive sleep apnea is immense,” Dr. Ghegan said. “One in five Americans is estimated to be afflicted with the disorder. On average, a person with obstructive sleep apnea has an event five times an hour.”
Obstructive sleep apnea can cause excessive daytime sleepiness in people who have the disorder. The market for products to combat the disorder totals in the neighborhood of $1.4 billion a year.
The public and the medical profession have become more and more aware of the disorder, Dr. Ghegan said. However, the only confirmatory test is a polysomnography procedure done in the laboratory.
He set out to perform a meta-analysis of studies done to test whether home sleep analysis equipment and procedures are useful tools when compared to the laboratory settings—noting that both the laboratory and the home settings have advantages and disadvantages.
Measuring Respiratory Distress
The primary goal of the meta-analysis was to compare the respiratory distress index (RDI) in the home studies with the laboratory studies.
The American Academy of Sleep Medicine rates the average number of obstructive sleep apnea events per hour as the respiratory distress index. An RDI of 0 to 5 is normal, 5 to 20 is mild, 20 to 40 is moderate, and over 40 is considered severe. An apnea event must last at least 10 seconds to be considered an event.
It is not uncommon to see RDIs well above 40. In some cases RDIs were well above 100, with events lasting as long as 90 to 120 seconds. During these bouts of apnea, blood oxygen saturation can fall well below normal levels.
Lab Setting Allows for Other Tests
“The laboratory setting remains the gold standard,” said Dr. Ghegan, because in the laboratory setting doctors may conduct other studies, an electroencephalogram (EEG), and other brain wave measurements. The laboratory setting, he noted, also allows doctors to perform nasal airflow analyses and oxygen saturation studies.
In addition to diagnosing obstructive sleep apnea, the studies in the laboratory may also uncover such conditions as narcolepsy or restless legs syndrome, he said.
On the other hand, Dr. Ghegan said, “The laboratory polysomnography is not readily available. There are long wait times for use of the laboratory and in rural communities there is a lack of access to the laboratories.”
The studies are also expensive, with costs averaging about $3000 for the study. Furthermore, patients are asked to perform the study in a strange sleep environment, which might skew the results. Dr. Ghegan also noted that the definition of what is an obstructive sleep disorder may vary from one organization to another.
Home Advantage: Convenience and Standardization
The home-based polysomnography studies have advantages in that they are simplified and are preformed in the person’s natural sleep environment. Even more of an advantage is that the home-based studies potentially eliminate the access-to-treatment barrier because there is no wait time and equipment is more readily available.
“Home sleep studies offer a less expensive and potentially more readily available option for the diagnosis of obstructive sleep apnea, however this may be offset by the increased incidence of poor recording.” – —Mark Ghegan, MD
“The home-based studies are less expensive, usually costing less than $1000 to perform, and the results are sent to a centralized center for data recording, decreasing the variability in the interpretation of the data,” Dr. Ghegan said.
The home-based equipment also received its validation when used in the largest cohort study, the Sleep Heart Health Study, he said.
The disadvantage to the home-based setup is that while it allows the study of obstructive sleep apnea, it does not allow study of other possible sleep disorders. The home-based study may also have a lower quality of data because it is not being monitored.
In his study, Dr. Ghegan designed the meta-analysis to included prospective cohort studies comparing the respiratory disturbance index of home sleep studies to that of laboratory polysomnography in the same patients undergoing evaluation for sleep disordered breathing.
Using Medline, he identified 28 papers in which home sleep studies and laboratory polysomnography were compared for differences in mean low oxygen saturation, sleep time, percentage of inadequate studies, and average cost per examination. Of those 28 papers, 12 were deemed sufficient to have the data necessary to make reasonable comparisons, Dr. Ghegan explained.
“On average, we found that the respiratory distress index was 10% higher in the patients who had the studies done in the laboratory,” Dr. Ghegan said. The odds rate was 0.90 and the 95% confidence index did not pass unity (0.87–0.92).
He also found that in the laboratory, sleep time was increased by 13% over the home-based studies.
Not surprisingly, there were more poor recordings in the home-based setting, Dr. Ghegan said, demonstrating that 15.7% of the home-based studies had a problem versus 6.2% in the laboratory studies. That difference reached statistical significance at the p = .001 level, he said.
On the other hand, the cost of doing the test at home was significantly less expensive that doing it in the laboratory, Dr. Ghegan illustrated. The cost savings for the home based system ranged from 35% to 88%.
There were no significant differences in the recording of oxygen saturation studies seen between the home and laboratory testing, he said.
“Based on the results of this meta-analysis,” Dr. Ghegan said, “home sleep studies may underestimate the severity of obstructive sleep apnea based on respiratory distress index values. However, that underestimation may not be of clinical significance.
“Home sleep studies offer a less expensive and potentially more readily available option for the diagnosis of obstructive sleep apnea, however this may be offset by the increased incidence of poor recording.”
©2006 The Triological Society