Aim: Obstructive sleep apnoea (OSA) is widely prevalent in patients with obesity, referred for bariatric surgery. Various clinical tools are clinically used for screening pre-operatively before referring for formal sleep studies. The aim of our observational analysis was to assess the usefulness of various screening methods for OSA used in clinical practice.
Methods: Records of all patients who had been referred to bariatric services in 2014 were reviewed. Various screening methods were used during clinical visits to justify investigating for OSA. Patients were referred for formal sleep studies to confirm OSA.
Results: Two hundred and twenty seven new patients were seen in medical bariatric clinics. Mean BMI was 47.6 (2882). 39 patients had already established CPAP treatment for OSA, hence excluded.104/188 had been assessed for OSA (and a further 22 have been referred and awaiting assessment). 35/104 (34%) did not have OSA; a further 13/104 (12%) had only mild OSA. 54% had severe OSA needing CPAP treatment: The sensitivity, specificity, positive and negative predictive values of various tests, with numbers tested are:
There was positive correlation between the BMI and presence of OSA (r=+0.2) and the severity of OSA (R=+0.15).
|Tests||n=||Sensitivity (%)||Specificity (%)||PPV (%)||NPV (%)|
|Sats on air <92%||72||8||87||57||30|
|STOP BANg ≥5||39||76||50||73||54|
|Epworth score >10||74||33||59||31||21|
Conclusion: The prevalence of OSA is high in obesity. Various commonly used respiratory screening tests may not accurately provide a pre-test probability for diagnosis of OSA. Formal overnight oximetry and sleep studies are required to diagnose this comorbidity in obesity, as it has implications during anaesthesia and post-op follow up.