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* From the Pulmonary Division, University Hospital of Zurich, Zurich, Switzerland.
Correspondence to: Konrad E. Bloch, MD, FCCP, Pulmonary Division, University Hospital of Zurich, Rämistrasse 100, 8091 Zurich, Switzerland; e-mail: pneubloc{at}usz.unizh.ch
Abstract
Objectives: Treatment of obstructive sleep apnea syndrome (OSA) is often delayed because polysomnography, the recommended standard diagnostic test, is not readily available. We evaluated whether the diagnosis of sleep apnea could be inferred from the response to a treatment trial with nasal continuous positive airway pressure (CPAP).
Design: Study on diagnostic accuracy.
Setting: Sleep-disorders clinic of a university hospital.
Patients: Seventy-six sleepy snorers consecutively referred for sleep apnea evaluation.
Interventions: CPAP treatment trial over 2 weeks as an initial diagnostic test in comparison with polysomnography, and treatment success over 
4 months.
Measurements and results: The main outcome was diagnostic accuracy of the CPAP trial. The trial result was positive if the patient had used CPAP for > 2 h per night and wished to continue therapy. This suggested sleep apnea. The trial was evaluated in terms of predicting an obstructive apnea/hypopnea index (AHI) > 10/h during polysomnography performed for validation, and in terms of identifying sleep apnea patients treated successfully over 4 months. Forty-four of 76 patients (58%) had sleep apnea as confirmed by an AHI > 10/h. The CPAP trial predicted sleep apnea with a sensitivity of 80%, a specificity of 97%, and positive and negative predictive values of 97% and 78%, respectively. In 35 of 76 sleep apnea patients (46%) with positive CPAP trial results, polysomnography could have been avoided. These patients were prescribed long-term CPAP therapy. After 4 months, 33 of 35 patients (94%) still used CPAP, and their symptoms remained improved. These patients were identified by the CPAP trial with positive and negative predictive values of 92% and 100%, respectively.
Conclusions: In a selected population, a CPAP trial may help to diagnose OSA, to identify patients who benefit from CPAP, and to reduce the need for polysomnography.
Key Words: continuous positive airway pressure • diagnosis • polysomnography • sleep apnea • treatment
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