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Chest. 2013 May;143(5):1284-1293. doi: 10.1378/chest.12-1132.

Serum bicarbonate level improves specificity of STOP-Bang screening for obstructive sleep apnea.

Author information

1
Department of Anesthesiology, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, ON, Canada. Electronic address: frances.chung@uhn.ca.
2
Department of Anesthesiology, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, ON, Canada.
3
Department of Anesthesiology, Dalhousie University and QEII Health Sciences Centre, Halifax, NS, Canada.
4
Sleep Disorders Center and the Section of Pulmonary and Critical Care Medicine, University of Chicago Pritzker School of Medicine, Chicago, IL.

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.

CONCLUSION:

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.

PMID:
23238577
DOI:
10.1378/chest.12-1132
[Indexed for MEDLINE]

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