Obstructive sleep apnoea (OSA) can be reliably diagnosed in the primary care setting with a portable nasal flow monitor in a model that offers an alternative to sleep specialist-led services, Australian research shows.
The Sydney OSA-GP study, led by the Woolcock Institute of Medical Research, first trained GPs to recognise OSA symptoms in their patients.
Likely OSA patients completed screening questionnaires, anthropometry, craniofacial photography and home sleep testing using a single channel, nasal flow monitor. All patients also underwent in-laboratory polysomnography (PSG) as the reference standard.
More than 60% of the 429 participants who completed testing were male, with a mean age of 49 years and a BMI of 30.
The study, published in Respirology, found the flow monitor was the best single measure (AUC 0.87) for predicting PSG diagnosed OSA.
“The addition of age, male, BMI and symptoms slightly increases the AUC observed with the flow monitor alone.”
The study said when using basic clinical and demographic information, 74% of those considered high risk will have OSA, but 36% considered low risk will also have OSA.
“With the addition of a simple, single-channel at-home nasal flow monitor, 85% of patients considered high-risk will have OSA, but 22% of those with a low-risk result on flow monitor may still have mild OSA,” the investigators said.
“Severe OSA (AHI≥30) can be confidently ruled out using our model that combines basic clinical and demographic information with the nasal flow monitor (NPV 96%), which is important as it has the highest potential to benefit from treatment.”
They found established patient questionnaires for OSA, anthropometrics and craniofacial photography do not add value to the assessment of OSA in the GP setting.
“Our data have shown that when screening questionnaires are given after the primary care physician has decided the patient requires testing, further evaluation may still be indicated even if the screening questionnaire indicates low risk, and in the Australian context referral to a specialist sleep physician should be considered.”
They concluded that diagnosis was unlikely to be possible without the use of a device, given a direct measure of airflow or a validated surrogate is required to rule-in OSA or rule-out severe disease.
An editorial in the journal said it was important to develop alternative models of diagnosis and management of OSA due to over-burdened specialist sleep services and limited access to laboratory-based sleep study testing.
“However, currently, it remains unclear how healthcare systems should be reshaped to accommodate a growing number of patients with undiagnosed OSA who are identified from primary care settings,” they said.
“Thus, in addition to improving diagnosis in primary care, primary care physicians could potentially take on an increasing role in the overall management of patients with OSA.”
They said until some of these challenges were ironed out, screening instruments such as the OSA50 and STOP-Bang questionnaires were likely to remain useful for identifying patients in primary care at high risk of moderate–severe OSA who are most likely to benefit from further investigation and treatment.