Original articleComparison of the NovaSom QSG™, a new sleep apnea home-diagnostic system, and polysomnography
Introduction
Obstructive sleep apnea (OSA) is a common disorder with significant morbidity and potential mortality occurring in 2–4% of middle-aged adults [1]. Patients with untreated OSA have a six- to 15-fold increased risk of motor vehicle accidents [2]. OSA is associated with a reduced quality of life [3], and is a contributor to hypertension [4], [5], [6] and cardiovascular events [7], [8].
Diagnosis and treatment of OSA can result in significant short-term and lifetime cost savings [9]. One study found that in the 10 years prior to diagnosis, OSA patients used approximately twice as many health care services as non-OSA patients [10]. Another group reported that in the year prior to diagnosis, medical costs were twice as much for untreated sleep apnea patients compared to age and sex matched controls [11].
Despite the clear advantages of diagnosis and treatment of OSA, certain potential limitations of in-lab polysomnography (PSG), the most commonly used diagnostic sleep procedure, may at times impede the diagnostic process. Some of these potential limitations include: the high cost of this technician-dependent procedure, patient acceptance of in-lab testing [12], potential for lengthy waiting periods, limited access in geographically remote regions, significant inter-scorer variability [13], [14], night-to-night variability in the apnea–hypopnea index (AHI) [15], and the tendency for predominantly supine PSGs to overestimate AHI due to the effect of position on breathing [16]. In addition, in many regions there are not enough sleep labs to address the demand using PSG. It is estimated that 1.17 million PSGs are performed each year in the US [17]. Given the prevalence of OSA, the current in-lab capacity cannot meet the need for diagnosis.
The significant increase in public and professional awareness of the increased costs, quality of life issues and dangers of untreated OSA has driven the need to find cost effective, clinically validated tests to supplement the current approach to diagnosis. One frequently considered strategy is to refer patients with a high pre-test probability of having OSA (e.g. regular loud snoring with witnessed apnea and high Epworth Sleepiness Score) for in-home evaluation.
There are many publications regarding ambulatory diagnostic systems and their validation to PSG. However, most of these studies were performed only in a lab setting [18], [19], [20], [21], which is a controlled environment compared to the home, where these devices are usually used. Most of the current devices require the patient to be hooked up in the lab or require technical assistance in the home in order to perform the study [20], [22]. Even with technical assistance, the data loss due to poor signal quality or signal loss was higher than if these studies had been performed in a lab setting [23]. We recently became aware of a new device specifically designed for self-administered home use, the NovaSom QSG, which we evaluated for reliability and validity in this study.
Section snippets
Materials and methods
Fifty-one consecutive adults referred to the sleep lab by a large pool of community physicians due to a clinical suspicion of OSA, based on symptoms including snoring, witnessed apnea and excessive daytime sleepiness, and scheduled for overnight in-lab PSG, signed informed consent to participate in the study. See Table 1 for subject characteristics and frequency of symptoms. All forms and procedures were approved by the Sequoia Hospital Institutional Review Board.
Patients performed a home
Results
Because no differences were present between subjects first using the NovaSom QSG at home vs. those first having in-lab testing, the data were pooled for analyses.
Of the 51 subjects, 45 completed in-lab PSG plus home NovaSom QSG. Six of the 51 subjects had no home data: three subjects returned their home systems unused and three subjects' NovaSom QSG data were lost due to a faulty memory chip. Forty-four of the 51 subjects had both PSG and in-lab NovaSom QSG data; seven subjects were missing
Discussion
This study attempts to compare the NovaSom QSG diagnostic system in the home and lab with conventional in-lab PSG. The study also examines the reliability of the NovaSom QSG by assessing the agreement among findings obtained on separate home study nights.
The data showed very high concordance between the in-lab NovaSom QSG and PSG when performed simultaneously in the lab. Sensitivity and negative predictive values of 95% and 96%, respectively, indicate that the NovaSom QSG is capable of
Acknowledgements
Financial support for this research was received from the Sequoia Hospital Pulmonary Research Fund.
References (30)
- et al.
Measurement error in visually scored electrophysiological data: respiration during sleep
J Neurosci Methods
(1984) Scoring variability between polysomnography technologists in different sleep laboratories
Sleep Med
(2002)- et al.
Mild to moderate sleep respiratory events – one night may not be enough
Chest
(2000) - et al.
Validation of a portable sleep apnea monitoring device
Chest
(1995) - et al.
Portable computerized polysomnography in attended and unattended settings
Chest
(1999) - et al.
Validation of the POLY-MESAM seven-channel ambulatory recording unit
Chest
(2000) - et al.
Clinical validation of the bedbug in detection of obstructive sleep apnea
Otolaryngol Head Neck Surg
(2001) - et al.
One negative polysomnogram does not exclude obstructive sleep apnea
Chest
(1993) - et al.
The occurrence of sleep-disordered breathing among middle-aged adults
N Engl J Med
(1993) - et al.
Sleepiness-related accidents in sleep apnea patients
Sleep
(2000)