Diagnostic accuracy of outpatient polygraphy devices : Acomparison with inpatient polysomnography in clinical routine

Abstract

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. Externally collected outpatient PG findings of 406patients were retrospectively compared with the corresponding PSG findings. Among the 406patients were 343men (85%) and 63women (15%), with mean age 50years. 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 35cases (9%) and unnecessary treatment initiated in 17cases (4%). The PG devices used showed acomparable diagnostic accuracy (r= 0.513-0.657), with asensitivity of 81.3-96.9% and aspecificity of 33.3-50.0%. 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.