Diagnostic accuracy of level 3 portable sleep tests versus level 1 polysomnography for sleep-disordered breathing: a systematic review and meta-analysis

Background:

Greater awareness of sleep-disordered breathing and rising obesity rates have fueled demand for sleep studies. Sleep testing using level 3 portable devices may expedite diagnosis and reduce the costs associated with level 1 in-laboratory polysomnography. We sought to assess the diagnostic accuracy of level 3 testing compared with level 1 testing and to identify the appropriate patient population for each test.

Methods:

We conducted a systematic review and meta-analysis of comparative studies of level 3 versus level 1 sleep tests in adults with suspected sleep-disordered breathing. We searched 3 research databases and grey literature sources for studies that reported on diagnostic accuracy parameters or disease management after diagnosis. Two reviewers screened the search results, selected potentially relevant studies and extracted data. We used a bivariate mixed-effects binary regression model to estimate summary diagnostic accuracy parameters.

Results:

We included 59 studies involving a total of 5026 evaluable patients (mostly patients suspected of having obstructive sleep apnea). Of these, 19 studies were included in the meta-analysis. The estimated area under the receiver operating characteristics curve was high, ranging between 0.85 and 0.99 across different levels of disease severity. Summary sensitivity ranged between 0.79 and 0.97, and summary specificity ranged between 0.60 and 0.93 across different apnea–hypopnea cut-offs. We saw no significant difference in the clinical management parameters between patients who underwent either test to receive their diagnosis.

Interpretation:

Level 3 portable devices showed good diagnostic performance compared with level 1 sleep tests in adult patients with a high pretest probability of moderate to severe obstructive sleep apnea and no unstable comorbidities. For patients suspected of having other types of sleep-disordered breathing or sleep disorders not related to breathing, level 1 testing remains the reference standard.Undiagnosed sleep-disordered breathing places a substantial burden on patients, families, health care systems and society.¹ Sleep fragmentation and recurrent hypoxemia cause daytime sleepiness and impaired concentration, which increase the risk of motor vehicle collisions and occupational accidents.^2–7 In addition, sleep-disordered breathing is associated with hypertension, stroke, cardiovascular disease, obesity and type 2 diabetes,^8–12 all of which involve greater use of health care resources.^13–17Obstructive sleep apnea is the most common type of sleep-disordered breathing. Narrowing of the upper airway during inspiration results in episodes of apnea (breathing cessation for at least 10 seconds), hypopnea (reduced airflow), oxygen desaturation and arousal from sleep due to respiratory effort.¹⁸ Clinical signs and symptoms include snoring, reports of nocturnal apnea, gasping or choking witnessed by a partner, daytime sleepiness, morning headaches and inability to concentrate. Patients with obesity or cardiovascular disease are at increased risk.¹⁹The severity of obstructive sleep apnea is usually graded using the apnea–hypopnea index (the mean number of apneas and hypopneas per hour of sleep) as follows: mild (5–14), moderate (15–29) and severe (≥ 30).^18,20Other, less common types of sleep-disordered breathing include upper airway resistance syndrome, obesity hyperventilation syndrome, central sleep apnea, and nocturnal hypoventilation/hypoxemia secondary to cardiopulmonary or neuromuscular disease. It is not uncommon for patients to have more than 1 type of sleep-disordered breathing.Estimates of the prevalence of sleep-disordered breathing vary depending on the population (e.g., by sex, age and comorbidities).²¹ According to the Wisconsin Sleep Cohort Study, values in American adults (aged 30–60 yr) are 24% for men and 9% for women.¹ A Canadian survey found a self-reported prevalence of sleep apnea of 3% among adults more than 18 years of age, and 5% among those more than 45 years of age.²² As the population ages and rates of obesity increase, the prevalence of sleep-disordered breathing is climbing.^1,19,23,24 Given its clinical implications, accurate diagnosis and treatment of the condition are critical.Level 1 sleep testing, or polysomnography, requires an overnight stay in a sleep laboratory with a technician in attendance. It captures a minimum of 7 channels of data (but typically ≥ 16), including respiratory, cardiovascular and neurologic parameters, to produce a comprehensive picture of sleep architecture. Level 1 is considered the reference standard for diagnosing all types of sleep-disordered breathing and sleep disorders.^19,25–27 However, limited facilities and the growing demand for sleep studies have resulted in long wait times.²⁸ Level 2 sleep testing uses level 1 equipment, but is performed without a technician in attendance.Level 3 testing uses portable monitors that allow sleep studies to be done at the patient’s home or elsewhere. This option was introduced as a more accessible and less expensive alternative to in-laboratory polysomnography. Level 3 devices record at least 3 channels of data (e.g., oximetry, airflow, respiratory effort). Unlike level 1, level 3 testing cannot measure the duration of sleep, the number of arousals or sleep stages, nor can it detect nonrespiratory sleep disorders.^27,29 Level 4 devices are also portable, but they capture less data — usually only 1 or 2 channels.^27,30We conducted a systematic review and meta-analysis to compare the diagnostic accuracy of the widely used level 3 portable monitors to in-laboratory polysomnography, and to determine the subpopulations of patients whose conditions might be most appropriately diagnosed with each test.