Clinical Inquiries

Sleep apnea in adults: How accurate is clinical prediction?

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EVIDENCE-BASED ANSWER

Moderately accurate, depending on which tool you use. Questionnaires, physical examination, and clinical prediction rules estimate the pretest probability of obstructive sleep apnea hypopnea syndrome (OSAHS), but are not specific enough to make the diagnosis (strength of recommendation [SOR]: B, meta-analyses, prospective cross-sectional studies). The Epworth Sleepiness Scale is a reliable measure of daytime sleepiness (SOR: B, factor analysis). The Berlin Questionnaire, Mallampati score, and truncal obesity can be used to assess pretest probability of OSAHS (SOR: B, multivariate analyses, cross-sectional studies).

Evidence summary

OSAHS is marked by daytime somnolence, snoring, difficult-to-control hypertension, refractory arrhythmias, angina, or heart failure.1 The syndrome is defined as an apnea-hypopnea index (AHI) of 5 or more events per hour during a sleep polysomnogram, accompanied by either excessive daytime sleepiness or 2 of the following: choking or gasping during sleep, recurrent awakenings from sleep, daytime fatigue, and impaired concentration.2

What questionnaires can tell you

The Epworth Sleepiness Scale rates the likelihood of dozing in 8 situations. Factor analysis of test-retest on 104 medical students and 150 patients with various sleep disorders showed that the scale was internally consistent but measured only daytime sleepiness.3

The Berlin Questionnaire assesses snoring, daytime sleepiness, history of hypertension, age, and body mass index (BMI). The questionnaire was evaluated in 744 adults presenting for unrelated problems at 5 primary care sites. Of 100 patients who underwent sleep studies, a finding of high risk on the Berlin Questionnaire predicted an AHI >5 with 86% sensitivity and 77% specificity, a positive likelihood ratio of 3.79.4

Mallampati scores, truncal obesity offer clues

Mallampati scoring grades visibility of the posterior pharynx when the patient opens his mouth and sticks out his tongue. Visibility is ranked on a scale of 1 to 4, with 1 representing the greatest visibility and 4 the least. Prospective multivariate assessment of Mallampati scores in adults referred to a sleep clinic yielded likelihood ratios of OSAHS for Mallampati grades 1 to 4 of 0.4, 0.7, 1.6, and 1.7, respectively.5

A cross-sectional study correlating OSAHS with truncal obesity in 192 patients referred to a sleep clinic found that the likelihood of OSAHS was 2.6 times greater if the waist-to-hip ratio was >1 in men and >0.85 in women.6

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Evidence-based answers from the Family Physicians Inquiries Network

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