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 of these 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.

Funding: Faculty of Biology and Medicine of the University of Lausanne, Lausanne University Hospital, Swiss National Science Foundation, Leenaards Foundation, GlaxoSmithKline, and Vaud Pulmonary League.