The NoSAS score for screening of sleep-disordered breathing: a derivation and validation study

Abstract

Background Diagnosis of sleep-disordered breathing requires overnight recordings, such as polygraphy or polysomnography. Considering the cost and low availability ofthese procedures, preselection of patients at high risk is recommended. We aimed to develop a screening tool allowing identification of individuals at risk of sleep-disordered breathing. Methods We used the participants from the population-based HypnoLaus cohort in Lausanne, Switzerland, who had a clinical assessment and polysomnography at home, to build a clinical score (the NoSAS score) using multiple factor analysis and logistic regression to identify people likely to have clinically significant sleep-disordered breathing. The NoSAS score was externally validated in an independent sleep cohort (EPISONO). We compared its performance to existing screening scores (STOP -Bang and Berlin scores). Findings We used the 2121 participants from the HypnoLaus cohort who were assessed between Sept 1,2009, and June 30, 2013. The NoSAS score, which ranges from 0 to 17, allocates 4 points for having a neck circumference of more than 40 cm, 3 points for having a body-mass index of 25 kg/m(2) to less than 30 kg/m(2) or 5 points for having a body -mass index of 30 kg/m(2) or more, 2 points for snoring, 4 points for being older than 55 years of age, and 2 points for being male. Using a threshold of 8 points or more, the NoSAS score identified individuals at risk of clinically significant sleep disordered breathing, with an area under the curve (AUC) of 0.74 (95% CI 0-72-0-76). It showed an even higher performance in the EPISONO cohort, with an AUC of 0.81 (0.77-0.85). The NoSAS score performed significantly better than did the STOP -Bang (AUC 0.67 [95% CI 0.65-0.69];p<0.0001) and Berlin (0.63 [0.61-0.66]

p<0.0001) scores. Interpretation The NoSAS score is a simple, efficient, and easy to implement score enabling identification of individuals at risk of sleep-disordered breathing. Because of its high discrimination power, the NoSAS score can help clinicians to decide which patients to further investigate with a nocturnal recording.