Type III home sleep testing versus pulse oximetry: is the respiratory disturbance index better than the oxygen desaturation index to predict the apnoea-hypopnoea index measured during laboratory polysomnography?

Objectives In its guidelines on the use of portable monitors to diagnose obstructive sleep apnoea, the American Academy of Sleep Medicine endorses home polygraphy with type III devices recording at a minimum airflow the respiratory effort and pulse oximetry, but advises against simple pulse oximetry. However, oximetry is widely available and simple to use in the home. This study was designed to compare the ability of the oxygen desaturation index (ODI) based on oximetry alone with a stand-alone pulse oximeter (SPO) and from the oximetry channel of the ApneaLink Plus (ALP), with the respiratory disturbance index (RDI) based on four channels from the ALP to predict the apnoea–hypopnoea index (AHI) from laboratory polysomnography. Design Cross-sectional diagnostic accuracy study. Setting Sleep medicine practice of a multispecialty clinic. Participants Patients referred for laboratory polysomnography with suspected sleep apnoea. We enrolled 135 participants with 123 attempting the home sleep testing and 73 having at least 4 hours of satisfactory data from SPO and ALP. Interventions Participants had home testing performed simultaneously with both a SPO and an ALP. The 2 oximeter probes were worn on different fingers of the same hand. The ODI for the SPO was calculated using Profox software (ODI SOX ). For the ALP, RDI and ODI were calculated using both technician scoring (RDI MAN and ODI MAN ) and the ALP computer scoring (RDI RAW and ODI RAW ). Results The receiver–operator characteristic areas under the curve for AHI ≥5 were RDI MAN 0.88 (95% confidence limits 0.81–0.96), RDI RAW 0.86 (0.76–0.94), ODI MAN 0.86 (0.77–0.95), ODI RAW 0.84 (0.75–0.93) and ODI SOX 0.83 (0.73–0.93). Conclusions We conclude that the RDI and the ODI, measured at home on the same night, give similar predictions of the laboratory AHI, measured on a different night. The differences between the two methods are small compared with the reported night-to-night variation of the AHI.