Background: Cardiorespiratory polysomnography (PSG) is considered the reference method for diagnosis of obstructive sleep apnea (OSA). Due to waiting times and high costs, payers increasingly request outpatient polygraphy (PG) as an alternative to inpatient PSG. The aim of the present study was to evaluate the diagnostic accuracy of different outpatient PG devices compared to stationary PSG in clinical practice.
Materials and methods: Externally collected outpatient PG findings of 406 patients were retrospectively compared with the corresponding PSG findings.
Results: Among the 406 patients were 343 men (85%) and 63 women (15%), with mean age 50 years. Mean body mass index (BMI) was 30 kg/m2. The rank correlation coefficient for PG- and PSG- derived apnea-hypopnea index (AHI) values was r = 0.574. On average, PG underestimated the AHI by 6.4 (±20.5) events/h. OSAS severity was determined correctly by PG in only 43% of cases. Sensitivity (90.7%) and specificity (45.2%) of ambulatory PG was calculated for the threshold value AHI ≥ 5/h. Based on the results of PG, an indicated therapy would have been omitted in 35 cases (9%) and unnecessary treatment initiated in 17 cases (4%). The PG devices used showed a comparable diagnostic accuracy (r = 0.513-0.657), with a sensitivity of 81.3-96.9% and a specificity of 33.3-50.0%.
Conclusion: Outpatient PG cannot reliably assess OSA severity in clinical routine. Confirmation by PSG in a sleep lab in symptomatic patients is obligatory. Outpatient PG devices should only be used as an upstream screening method. The automatic evaluation of the PG should always be proofed.
Keywords: CPAP; Intrinsic sleep disorders; Obstructive sleep apnea syndrome; Respiration disorders; Sleep-disordered breathing.