A Decision Rule for Diagnostic Testing in Obstructive Sleep Apnea

Abstract

1 or more) of 5.17% and 81%, respectively. In contrast, night polysomnography. Decision rules may provide an alternative patients with the lowest clinical score had a likelihood ratio to polysomnography. A consecutive series of patients referred to of 0.25 and a post-test probability of OSA of 17%. a tertiary sleep center underwent prospective evaluation with the A morphometric model developed by Kushida and col- upper airway physical examination protocol, followed by determi- leagues had an OSA diagnostic sensitivity and specificity of nation of the respiratory disturbance index using a portable moni- 98% and 100%, respectively; however, selection bias was a tor. Seventy-five patients were evaluated with the upper airway potential concern (3). Nevertheless, the model illustrated the physical examination protocol. Historic predictors included age, potential value of physical examination-based decision rules snoring, witnessed apneas, and hypertension. Physical examination- in clinical decision-making. based predictors included body mass index, neck circumference, Current decision rules have only intermediate diagnostic mandibular protrusion, thyro-rami distance, sterno-mental distance, characteristics and are frequently too cumbersome, either sterno-mental displacement, thyro-mental displacement, cricomen- tal space, pharyngeal grade, Sampsoon-Young classification, and over- arithmetically or logistically, for bedside implementation (2, bite. A decision rule was developed using three predictors: a crico- 4-10). The objective of this study was to develop a standard- mental space of 1.5 cm or less, a pharyngeal grade of more than II, ized approach toward patient assessment in the OSA setting, and the presence of overbite. In patients with all three predictors with a specific emphasis on ease of use for the bedside clini- (17%), the decision rule had a positive predictive value of 95% cian. Predictors of OSA were identified, and a decision rule (95% confidence interval (CI), 75-100%) and a negative predictive was developed. value of 49% (95% CI, 35-63%). A cricomental space of more than 1.5 cm (27% of patients) excluded OSA (negative predictive value METHODS of 100%, 95% CI, 75-100%). Comparable performance was obtained in a validation sample of 50 patients referred for diagnostic testing. Subjects were recruited from the Alberta Lung Association Sleep Cen- This decision rule provides a simple, reliable, and accurate method tre (ALASC), which is the major sleep center in Southern Alberta. of identifying a subset patients with, and perhaps more importantly, Referrals to the sleep center were assigned to one of four sleep physi- without OSA. cians on a consecutive basis; that is, there was no systematic physician- patient allocation. The two physicians (W.H.T. and J.E.R.) participating