PURPOSE: STOP-Bang questionnaire is a sensitive screening tool for obstructive sleep apnea (OSA) in surgical patients.1 This study is to explore the possibility to improve specificity of STOP-Bang by incorporating hemoglobin (Hb) level.
METHODS: Following hospital ethics approval, eligible patients were approached at preoperative clinics. The consented patients were asked to answer STOP-Bang questionnaire1 (Snoring, Tiredness, Observed Apnea, high blood Pressure) and invited to undergo overnight portable polysomnography (PSG) (Embeltta X-100) for research purpose. The BMI, age, neck circumference and male gender (Bang) were documented by research staff. Preoperative Hb level was extracted through chart review. Predictive performance of different combinations of STOP-Bang score and Hb level had been analyzed. A total of 383 with complete data were included.
RESULTS: The age was 60 ± 11 years; 46% males; BMI 30.9 ± 6.9 kg/m2; neck circumference 39 ± 4 cm; Hb 136 ±15 g/L. Of them, AHI>5: 275 (72%); AHI>15: 158 (41%) and AHI>30: 72(19%).To ensure a specificity over 90%, a Hb value ≥150 for females and ≥160 for males was chosen as cut-off. The specificity of STOP-Bang ≥3 for AHI > 5(all OSA patients) and AHI > 30 (severe OSA patients) was 35% (CI:26-82) and 24% (CI:19-29). The sensitivity was 85% (CI: 81-89) and 93%(CI:87-99).With combination of STOP-Bang ≥3 and Hb ≥ cut-off , the specificity for AHI > 5 and AHI > 30 increased to 94%(CI:90-99) and 92%(CI:89-95). However, the sensitivity decreased . With STOP-Bang ≥6 as cut-off, specificity of STOP-Bang increased to 86% (CI:80-93) and 86% (CI:82-90) respectively, at cost of a decreased sensitivity. With STOP-Bang ≥6 or STOP-Bang≥3 plus Hb ≥ cut-off, more patients were detected and the specificity was 82% (CI: 74-89) and 80% (CI:76-85).
CONCLUSIONS: The patients with STOP-Bang<3 had very low chance to have OSA. The patients with STOP-Bang≥6 or STOP-Bang≥3 with Hb≥150 in females or Hb≥160 in males are most likely to have OSA.
CLINICAL IMPLICATIONS: A 2-step screening strategy can be adopted for OSA screening. Reference 1.Anesthesiology 2008 108, 812-821.
DISCLOSURE: Frances Chung: Grant monies (from sources other than industry): University Health Network Foundation, Grant monies (from sources other than industry): Physician Service Incoporation, Grant monies (from industry related sources): ResMed Foundation
The following authors have nothing to disclose: Pu Liao, Yiliang Yang, Hisham Elsaid, Sazzadul Islam
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