From the Guidelines
For a patient with suspected sleep apnea, the primary diagnostic test that should be ordered is a sleep study, specifically overnight polysomnography (PSG) or a home sleep apnea test (HSAT), as recommended by the most recent study 1. This comprehensive diagnostic approach is essential to determine the presence and severity of sleep apnea, which can significantly impact morbidity, mortality, and quality of life. The choice between PSG and HSAT depends on the patient's specific condition and the availability of resources. PSG is considered the gold standard for diagnosing sleep apnea, as it provides a detailed assessment of various physiological parameters during sleep, including brain activity, eye movements, heart rate, blood oxygen levels, breathing patterns, and body movements. HSAT, on the other hand, is a more portable and convenient option that can be used for patients with a high pre-test probability of moderate to severe obstructive sleep apnea who do not have significant comorbidities. Additional diagnostics may include:
- A comprehensive medical history focusing on sleep patterns, daytime sleepiness, and snoring
- Physical examination with attention to BMI, neck circumference, and upper airway evaluation
- Screening questionnaires such as the STOP-BANG or Epworth Sleepiness Scale
- Laboratory tests, including thyroid function tests, to rule out other conditions that could cause similar symptoms
- Arterial blood gas analysis in patients with suspected hypoventilation These diagnostic approaches are crucial because untreated sleep apnea increases the risk of cardiovascular disease, stroke, and accidents due to daytime sleepiness, while proper diagnosis enables appropriate treatment with CPAP, oral appliances, or surgical interventions, ultimately improving morbidity, mortality, and quality of life outcomes.
From the Research
Diagnostic Tests for Suspected Sleep Apnea
The following diagnostic tests can be ordered for a patient with suspected sleep apnea:
- Polysomnography (PSG): a comprehensive sleep study that measures various sleep variables, including the apnea-hypopnea index (AHI) 2
- Home Sleep Apnea Test (HSAT): a portable device that measures sleep variables, including AHI, in the patient's home environment 3, 4, 5
- Home Sleep Test (HST): a less expensive and easier to perform alternative to PSG, which can be used to diagnose obstructive sleep apnea (OSA) in patients with high pretest probability without certain comorbidities 5
Indications for Diagnostic Tests
The choice of diagnostic test depends on various factors, including:
- Patient characteristics, such as age, body mass index (BMI), and medical history 3, 4
- Clinical symptoms, such as excessive daytime sleepiness and snoring 2
- Presence of comorbidities, such as severe pulmonary disease, congestive heart failure, or neuromuscular weakness 3
- Previous diagnostic test results, such as a negative PSG or HSAT 3, 4
Interpretation of Diagnostic Test Results
The results of diagnostic tests should be interpreted in the context of the patient's clinical symptoms and medical history. For example:
- A positive HSAT result, defined as an AHI greater than or equal to 5 events/h, indicates the presence of OSA 3
- A negative PSG result does not necessarily rule out OSA, as some patients may have a false-negative result 3
- Older age and hypertension are predictors of OSA on HSAT in patients with an initial negative PSG 3