Elsevier

Sleep Medicine

Volume 4, Issue 3, May 2003, Pages 213-218
Sleep Medicine

Original article
Comparison of the NovaSom QSG™, a new sleep apnea home-diagnostic system, and polysomnography

https://doi.org/10.1016/S1389-9457(02)00234-4Get rights and content

Abstract

Background: Obstructive sleep apnea (OSA) is a serious, common, and underdiagnosed disorder that challenges health care resources. While polysomnography (PSG) represents the standard diagnostic test for OSA, portable devices provide an alternative diagnostic tool when issues of cost, time, geographic availability, or other constraints pose impediments to in-lab testing. This study compares the NovaSom QSG™, a new sleep apnea home diagnostic system, to PSG both in the laboratory and in the home.

Methods: Fifty-one consecutive adults referred to the sleep lab for suspicion of OSA underwent one night of in-lab, simultaneous recording of PSG and NovaSom QSG in addition to using the NovaSom QSG at home for three nights. Two separate comparisons were made using the apnea–hypopnea index (AHI): in-lab PSG to in-lab NovaSom QSG and in-lab PSG to home NovaSom QSG.

Results: Using a clinical cut-off of AHI=15, the sensitivity and specificity of the in-lab NovaSom QSG vs. PSG were 95% and 91%, respectively. For home NovaSom QSG vs. in-lab PSG, the sensitivity was 91% and specificity was 83%. The intra-class correlation coefficient for the agreement between three separate nights of NovaSom QSG home data was 0.88.

Conclusions: In a patient population suspected of having OSA, the NovaSom QSG demonstrated acceptable sensitivity and specificity both in the lab and self-administered in the home, when compared to PSG.

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.

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