We acknowledge that the use of simulated level 3 studies derived from in-laboratory PSG rather than actual HST was a potential limitation of our study. We also agree that the rate of technical failure is probably higher with level 3 HST because of the absence of an attending technician; however, we disagree with Dr. Goldstein's assertion that the technical specifications, and hence data quality, from level 3 HST devices are inferior to those of level 1 PSG. The fidelity of modern level 3 devices has advanced substantially, enabling data to be recorded at similar specifications as laboratory PSG. Level 1 respiratory data for our study were collected at 16-bit resolution and 32 Hz, whereas the NOX-T3 level 3 device (BD), for example, can record at 24-bit resolution and 256 Hz. Furthermore, a recent meta-analysis has confirmed high diagnostic accuracy of level 3 HST devices, reporting a receiver-operating characteristic area under the curve greater than 0.90 for all cutoffs for severity of the apnea–hypopnea index in almost all studies (1). As such, we also disagree with Dr. Goldstein that physicians would have less confidence in data quality from level 3 HST.
- sleep apnea
- research laboratories