Preliminary Screening For Obstructive Sleep Apnoea In Primary Care – Why Do It?
Treating symptomatic obstructive sleep apnoea (OSAS) is highly rewarding and can make enormous differences to patients’ quality of life. This is why NICE felt that such patients should all be offered treatment with continuous positive airway pressure (CPAP) – technology appraisal 139, https://www.nice.org.uk/guidance/ta139/chapter/1-Guidance).
Following this NICE appraisal and better recognition of OSAS, referrals for diagnostic sleep studies to identify obstructive sleep apnoea (OSA) have risen considerably, such that most sleep units cannot cope with the workload, despite moving from hospital to home sleep studies. This often requires two visits to the hospital, to collect and return the equipment. Investigation nearer home would be much appreciated by patients.
Patients that would benefit from treatment, especially CPAP whilst asleep, are sometimes hard to identify. This uncertainty over spotting appropriate patients for referral to secondary care means that many patients are seen who perhaps might not need such a referral, and some relevant patients are missed. The prevalence of OSA is so high (it is estimated that around 5% of adults have severe enough OSA such that they would benefit from treatment) that it is unlikely that secondary care will ever receive the necessary funding to manage the current referral patterns.
It is therefore very likely that some aspect of screening for symptomatic OSA should go on in general practice as part of the decision to refer. This will only happen of course if the initial screening is not time-consuming, and/or reimbursed if it does require extra time or resources. A practice of say 10,000 patients might expect to have well over 400 who, based on their symptoms, would probably need a sleep study to confirm, or otherwise, significant OSAS.
A recent article in the British Journal of General Practice highlighted the arguments for moving to a primary care-based approach to screening for OSA.
The purpose of this article is to describe the three ways a general practice might screen patients for OSA and possible onward referral for treatment. They represent increasing GP involvement in the process.
- Use a pair of simple questionnaires to assess a) whether OSA is likely, and b) whether there is excessive sleepiness likely to necessitate treatment.
- Use a simple home sleep monitor given out by the practice, but analysed (in conjunction with a short questionnaire) by the local sleep centre who decide on the need for further management.
- Use a simple home sleep monitor and learn to interpret the results, thus triaging who should benefit from referral to secondary care for treatment.
1. Questionnaires only
There are two questionnaires that have gained credibility as useful tools in identifying sleep apnoea and sleepiness (the dominant symptom benefitting from treatment), the STOPBANG and EPWORTH. The STOPBANG is an 8 point tool that assesses whether someone is likely to have OSA, it incorporates symptom questions, anthropometric data and blood pressure.
http://www.stopbang.ca/osa/screening.php is the official site and allows one to fill in the data and obtain a rating as to whether there is a high, medium of low chance of having OSA.
The EPWORTH score or scale is an 8 point questionnaire where patients rate their tendency to nod off in certain circumstances. Each answer is scaled 0 to 3 and thus the whole questionnaire is scaled 0 to 24. Although the boundary between normal and sleepy is very blurred it is generally reckoned that a score of 10 or more is increasingly abnormal (but can of course be due to lifestyle issues and not just a medical condition). This is an unofficial site but does allow one to fill in the questionnaire and get the score. https://qxmd.com/calculate/calculator_85/epworth-sleepiness-scale or http://www.bestinfosite.com/ess.htm .
The correct and official wording for the score is on https://www.gpnotebook.co.uk/. Further information on the ESS is available here http://epworthsleepinessscale.com/about-the-ess/
There is a shorter alternative to the STOPBANG, the OSA50, which may be almost as good, but has not achieved the same acceptance. A score of 5 or above is deemed positive. http://www.sahealth.sa.gov.au/wps/wcm/connect/
It is important to realise that as with every such simple tool there will be patients who do not give representative scores for whatever reason (and who may need help filling it in) and results requiring intelligent interpretation. Several commissioning organisations request that such preliminary tools are used prior to referrals, some unfortunately using inappropriate questionnaires and thresholds for referral, despite recommendations to the contrary.
https://cks.nice.org.uk/obstructive-sleep-apnoea-syndrome#!scenario, https://www.sleepsociety.org.uk/wp-content/uploads/2015/07/OSA-Toolkit-2015-FINAL.pdf, http://www.ipswichandeastsuffolkccg.nhs.uk/
2. Questionnaire and simple home sleep study, recording sent to secondary care.
If the above simple screening system suggests OSA (or if, despite a low score, there is still a strong suspicion there may be OSA), then progressing to a simple sleep study is appropriate. Opinion varies on the best approach, and whether such tests can ever be definitive. In our opinion, if used in conjunction with the questionnaires, a further more detailed history if necessary, and an understanding of the limitations of a simple sleep study, then such an approach is entirely valid. There will always be some ‘middling’ or equivocal results from simple sleep studies that require further investigation. These devices give digital data that can be sent to the secondary care service for analysis, along with the results of the STOPBANG and EPWORTH questionnaires. Further information can also be sent; e.g. whether the patient is a professional driver is also useful in deciding how urgently to refer and see. https://cks.nice.org.uk/obstructive-sleep-apnoea-syndrome#!scenario
The simplest home screening tool, with consequently the most limitations, is overnight oximetry alone. These devices can monitor and store both oxygen levels and pulse rate all night for downloading the following morning. Apnoeas and hypopnoeas tend to cause recognisable dips in oxygen levels, and the consequent recurrent arousals tend to cause pulse rate rises. These recording oximeters and accompanying software (or smartphone app) can be very cheap, some under £200 (e.g. https://www.viatomtech.com/checkme-o2) . However, not all these cheap monitors have been tested properly. Those that have, tend to be more expensive of course, e.g. https://stowood.com/product/konica-minolta-pulsox-300i/ .
This paper is a good example of research project demonstrating the success of a questionnaire followed by overnight oximetry. https://thorax.bmj.com/content/thoraxjnl/66/3/213.full.pdf
The more sophisticated devices suitable for home screening measure oxygen saturation and heart rate along with other signals such as snoring, nasal flow, body position and sometimes further signals that necessarily increase cost and complexity for the patient. There are many such devices with varying degrees of supporting evidence, examples: https://stowood.com/product/visi-black-series/ and https://www.resmed.com/uk/en/healthcare-professional/products/diagnostics/apnealink-air.html .
3. Questionnaire and simple home sleep study, recording analysed in primary care.
The text in section 2 applies here except that the analysis is performed by the GP. Such a service may not be just for one practice, but be a resource for other practices too. In this situation the GP will of course have spent an appropriate amount of time learning how to interpret whichever screening tool they choose to use, along with further education on sleep apnoea and related conditions.
As with method 2, remuneration will be required to be switched from secondary to primary care. There are examples of GPs running such services (Koefman and Siddiqui and Gadhia). However, there may be issues liaising with the secondary care unit, who may be concerned (rightly or wrongly) about the quality of the studies and their interpretation. Thus discussions with the secondary care unit, prior to designing such a service, are, in our view, vital.
In summary, there are several approaches to solving the problem of increasing requirements for the diagnosis and treatment of OSA, three of which are described here. Involvement by GPs and their staff needs appropriate remuneration, transferred from secondary or tertiary care. Increasingly sophisticated and easy-to-use devices are making such home studies more viable.
The web links provided should provide some of the information required to build a case to start such a service.
“If the driver of the truck that killed my nephew had been diagnosed and referred for fast track treatment of OSA when he visited his GP to complain about being tired all the time, Toby would still be with us”.