Utility of Nosas Score as a Screening Tool to Suspect Obstructive Sleep Apnea in Comparison with Stop-Bang Questionnaire
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Abstract
Background:
Obstructive Sleep Apnea (OSA) is a commonly yet poorly diagnosed, sleep-related breathing disorder with characteristics of periodic blockage of upper airways during sleep, which leads to periodic hypoxia and sleep fragmentation. OSA is closely linked with obesity and growing age and leads to cardiovascular and metabolic morbidity. Even though polysomnography (PSG) is the gold standard diagnostic modality, its restricted accessibility requires the application of simple and reliable screening tools. High sensitivity leads to the widespread use of the STOP-BANG questionnaire, but a simple alternative has been suggested as the NoSAS score, predominantly based on objective anthropometric parameters.
Objective:
To evaluate the diagnostic utility of the NoSAS score in screening obstructive sleep apnea and to compare its performance with the STOP-BANG questionnaire among obese adults suspected of OSA.
Materials and methods:
A cross-sectional study was carried out in the Department of Pulmonary Medicine at a tertiary care teaching hospital over 18 months (January 2022 - June 2023). Overall, 120 adults aged 18-65 years with a body mass index of more than 30 kg/m2 and with symptoms indicative of OSA were recruited. Socio-demographic profile, anthropometric measurements and clinical history were noted. All subjects were evaluated in terms of NoSAS score as well as the STOP-BANG questionnaire, and then overnight polysomnography was conducted. The severity of OSA was determined through the Apnea-Hypopnea Index (AHI). The chi-square test, ANOVA and Receiver Operating Characteristic (ROC) curve analysis were statistical analyses employed to determine the diagnostic accuracy.
Results:
There was a significant association between advancing age and progressive OSA severity (p < 0.001), with severe OSA constituting most of the cases. The average NoSAS score increased considerably with higher BMI categories (p = 0.040), revealing a strong correlation with the severity of obesity. The analysis of ROC curves demonstrated that the two screening tools have a similar diagnostic performance. In moderate-to-severe OSA, the NoSAS score had an AUC of 0.746 when compared to 0.783 for STOP-BANG (p = 0.488). To detect overall OSA, AUC of NoSAS was 0.774, and for STOP-BANG was 0.707 (p = 0.999), which was not statistically significant.
Conclusion:
The NoSAS score had a diagnostic accuracy similar to the STOP-BANG questionnaire in the screening of obstructive sleep apnea. The NoSAS score is a useful and convenient screening instrument because of its simplicity, objectivity, and applicability in obese populations as well as in resource-limited clinical settings, with the potential to minimize unnecessary referrals for polysomnography.