title: Serum bicarbonate level improves specificity of STOP-Bang screening for obstructive sleep apnea.
abstract: BACKGROUND
  The STOP-Bang questionnaire is a validated screening tool for the identification of surgical patients with obstructive sleep apnea (OSA). A STOP-Bang score ≥ 3 is highly sensitive but only moderately specific. Apnea/hypopnea during sleep can lead to intermittent hypercapnia and may result in serum bicarbonate (HCO₃⁻) retention. The addition of serum HCO₃⁻ level to the STOP-Bang questionnaire may improve its specificity.
  
  
  METHODS
  Four thousand seventy-seven preoperative patients were approached for consent and screened by the STOP-Bang questionnaire. Polysomnography was performed and preoperative HCO₃⁻ level was collected in 384 patients. Study participants were randomly assigned to a derivation or validation cohort. Predictive parameters (sensitivity, specificity, positive and negative predictive values) for STOP-Bang score and serum HCO₃⁻ level were calculated.
  
  
  RESULTS
  In the derivation cohort, with a STOP-Bang score ≥ 3, the specificity for all OSA, moderate/severe OSA, and severe OSA was 37.0%, 30.4%, and 27.7%, respectively. HCO₃⁻ level of 28 mmol/L was selected as a cutoff for analysis. With the addition of HCO₃⁻ level ≥ 28 mmol/L to the STOP-Bang score ≥ 3, the specificity for all OSA, moderate/severe OSA, and severe OSA improved to 85.2%, 81.7%, and 79.7%, respectively. Similar improvement was observed in the validation cohort.
  
  
  CONCLUSIONS
  Serum HCO₃⁻ level increases the specificity of STOP-Bang screening in predicting moderate/severe OSA. We propose a two-step screening process. The first step uses a STOP-Bang score to screen patients, and the second step uses serum HCO₃⁻ level in those with a STOP-Bang score ≥ 3 for increased specificity.
authors.affiliation: Department of Anesthesiology, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, ON, Canada. Electronic address: frances.chung@uhn.ca.
authors.forename: Frances
authors.initials: F
authors.lastname: Chung
authors.affiliation: Department of Anesthesiology, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, ON, Canada.
authors.forename: Edmond
authors.initials: E
authors.lastname: Chau
authors.affiliation: Department of Anesthesiology, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, ON, Canada.
authors.forename: Yiliang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Anesthesiology, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, ON, Canada.
authors.forename: Pu
authors.initials: P
authors.lastname: Liao
authors.affiliation: Department of Anesthesiology, Dalhousie University and QEII Health Sciences Centre, Halifax, NS, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Hall
authors.affiliation: Sleep Disorders Center and the Section of Pulmonary and Critical Care Medicine, University of Chicago Pritzker School of Medicine, Chicago, IL.
authors.forename: Babak
authors.initials: B
authors.lastname: Mokhlesi
mesh_terms: D000328:Adult; D000368:Aged; D001639:Bicarbonates / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D017286:Polysomnography; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000097:blood / Q000175:diagnosis*; D011795:Surveys and Questionnaires
chemical_list: D001639:Bicarbonates; D015415:Biomarkers