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Risk for Obstructive Sleep Apnea
- Nikolaus C. Netzer, MD; and
- Kingman P. Strohl, MD
- Case Western Reserve University; Cleveland, OH 44106 (Netzer) Case Western Reserve University; Cleveland, OH 44106 (Strohl)
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IN RESPONSE:
We thank Drs. Tamarin and Brandstetter for the classical reference. Of interest, the public considers excessive sleepiness to be more important than physicians do (1).
Dr. Nardone and Drs. Strauss and Browner point out the substantial effect that disease prevalence will have on the operation of the Berlin Questionnaire. The Figure and Table 4 in our report present the operating characteristics, including likelihood ratios (2), of the Berlin Questionnaire only in the subgroup, which was overrepresented by persons at high risk. The correspondents agree with us about the likelihood ratio of a patient without a target number of events during sleep compared with those with a target number. We agree that the Berlin Questionnaire can provide confidence in the supposition that an RDI greater than 5 is unlikely in the lower-risk group. At issue is the prevalence of sleep apnea syndrome in the high-risk group.
The 2% to 4% prevalence is derived from population-based studies (1). The prevalence in primary care populations is much higher. The definition of sleep apnea syndrome is driven by symptoms (3), and in our survey the average prevalence of high risk across five practices was 37%. The Figure in our report suggests that 90% of these people will have an RDI greater than 5, meeting the disease definition (3). Thus, we estimate that in the entire group, the post-test probability that the high-risk patient will meet the disease definition is greater than 60%; this value is within a moderately useful range for clinical decisions (2).
Why might the prevalence be higher in primary care? One reason is the ecology of a medical practice in which many encounters (>85%) are for chronic and acute disease (4). This results in an enriched profile for risk factors. Fifty percent of our patients were obese or hypertensive, or both (that is, positive in category 3 alone), and 42% and 31% were positive in category 1 and category 2, respectively (our Table 3).
The Berlin Questionnaire was not designed to replace clinical reasoning. Patients who are not obese or do not have hypertension or the Pickwickian syndrome are not immune from the sleep apnea syndrome (1), nor do we think it prudent to ignore drowsy driving. We live in an interesting time to report that one third of patients met criteria for a sleep study, which many believe is too expensive. Patients who have car crashes caused by sleepiness, hypertension uncontrolled by drugs, nocturnal angina, and unexplained peripheral edema might immediately benefit from diagnosis. However, we know that people with just snoring and sleepiness will feel better with treatment (1). Now our focus has shifted to “thresholds” for management and testing.
Nikolaus C. Netzer, MD
Case Western Reserve University; Cleveland, OH 44106
Kingman P. Strohl, MD
Case Western Reserve University; Cleveland, OH 44106
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
•Include no more than 300 words of text, three authors, and five references
•Type with double-spacing
•Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.
Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
Annals welcomes electronically submitted letters.
- Copyright ©2004 by the American College of Physicians
