Portable Monitors in the Diagnosis of Obstructive Sleep Apnea* Murtuza Ahmed, MD; Nirav P. Patel, MD; and Ilene Rosen, MD, MSCE

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1 Topics in Practice Management Portable Monitors in the Diagnosis of Obstructive Sleep Apnea* Murtuza Ahmed, MD; Nirav P. Patel, MD; and Ilene Rosen, MD, MSCE The use of portable monitors (PM) devices has been demonstrated in a wide variety of investigational settings with varying results. While most devices correlate very well with in-laboratory polysomnography, some still misclassify a significant numbers of patients and have lower sensitivity. In addition, the failure rate of PM devices is higher than that of in-laboratory polysomnography, requiring repeated investigations. Nonetheless, these devices may reduce the waiting time for diagnosis and could potentially decrease costs. Cost-effectiveness studies have yet to demonstrate an advantage to using PM devices, although their employed modeling techniques may not accurately reflect prevailing practices. The majority of third-party payers do not reimburse unattended studies and consider them still to be investigational. Some health maintenance organizations have begun to recognize PM-based studies in their diagnostic algorithms and will cover their cost; others may do so on a case-by-case basis. There continues to be a dearth of evidence to support widespread implementation of PM devices for use within the general population. Larger-scale validation studies in patients with lower pretest probabilities and a wide range of comorbidities are needed. (CHEST 2007; 132: ) Key words: cost; diagnosis; home polysomnography; methods; obstructive sleep apnea; portable monitors; practice guidelines; review Abbreviations: AASM American Academy of Sleep Medicine; ACCP American College of Chest Physicians; AHI apnea-hypopnea index; ATS American Thoracic Society; CMS Centers for Medicare and Medicaid Services; OSA obstructive sleep apnea; PM portable monitor; RDI respiratory disturbance index; SHHS Sleep Heart Health Study Obstructive sleep apnea (OSA) is a major public health problem, affecting up to 5% of the world population 1 and between 2% and 4% of adults in the United States. 2 OSA has wide ranging consequences, including increased risk of motor vehicle accidents 3 and adverse cardiovascular risk. 1 More recently, increased risk for sudden cardiac death during the sleeping hours 4 as well as increased overall mortality rate among untreated individuals 5 have been shown. *From the Division of Sleep Medicine, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA. The authors have no conflicts of interest to disclose. Manuscript received November 16, 2006; revision accepted June 29, Reproduction of this article is prohibited without written permission from the American College of Chest Physicians ( org/misc/reprints.shtml). Correspondence to: Murtuza Ahmed, MD, Division of Sleep Medicine, Department of Medicine, University of Pennsylvania School of Medicine, 3624 Market St, Suite 205, Philadelphia, PA 19104; Murtuza.Ahmed@uphs.upenn.edu DOI: /chest While clinicians have increasingly turned their attention to this syndrome, and referrals to sleep clinics for diagnostic evaluations have increased dramatically, the infrastructure to support them has not. 6 Time is of the essence: as many as 82% of men and 93% of women with moderate-to-severe sleep apnea For editorial comment see page 1418 have not received a diagnosis, as estimated by data from the Wisconsin Sleep Cohort study. 7 Patients may have sleep apnea for up to 7 years before coming to medical attention and wait up to an additional 8 months before seeing a sleep specialist. 8 Current diagnostic criteria for OSA continue to employ full in-laboratory polysomnography. 9,10 Critics of this approach maintain that long wait times at most sleep centers have become the norm. 6 While there are some authors 11 who have suggested that many sleep laboratories in the United States are 1672 Topics in Practice Management

2 indeed able to schedule patients for studies within 1 to 3 weeks, this may not be the case in other countries. Nonetheless, the costs associated with conducting in-laboratory polysomnography remain high. 12 While clinical prediction rules have been generated to aid in screening and selecting patients for polysomnography, 13,14 these have yet to be widely adopted in clinical practice. Many practitioners have looked to alternative methods of diagnosis that would provide a precise and highly accurate diagnosis of OSA at much lower cost. Split-night study protocols have been developed as one way of streamlining the approach to diagnosis and treatment of OSA, but they do not provide a complete solution. 15 This article focuses on the clinical use of portable monitor (PM) devices to diagnose OSA, reviews recent guidelines and literature, and considers billing and reimbursement status. PM Devices PM devices have been in investigational use for the diagnosis of OSA for 2 decades. As the technology has matured, they are now a more feasible option in the diagnosis and management of OSA. The arguments for widespread adoption of PM devices are manifold. Deployment of these devices in clinical practice could potentially mitigate access problems that are now the major bottlenecks in the diagnosis and subsequent treatment for OSA. By using more unattended PM devices, the higher costs of attended in-laboratory polysomnography could also possibly be reduced. Furthermore, delays to therapy would be reduced. Other benefits include the comfort and convenience of sleeping in one s own bed, and therefore possibly achieving a night of sleep more representative of the patient s norms. However, there are several limitations of PM devices that must be considered as well. These include the inherent lack of an attendant during the study, which may potentially affect data quality. In addition, the most widely used applications of PM technology do not have EEG channels and are unable to assess sleep architecture or staging. This inability does not allow for the computation of the apnea-hypopnea index (AHI) because total sleep time cannot be calculated. Only total time in bed can be ascertained, and therefore PM devices report respiratory disturbance index (RDI) values to infer apnea severity. Other disturbances during sleep, such as surreptitious seizure activity or arousal indexes, also cannot be assessed. The large number of devices, manufacturers, channel configurations, and scoring schemes result in further variability. For most devices, there still is a lack of adequate validation data in larger samples of patients. There is also disagreement among investigators as to how the RDI generated from a PM can be compared statistically with an AHI because there is a lack of direct equivalency between the two ratios. 16 Finally, studies examining the long-term outcome of patients who receive a diagnosis using PM devices have yet to be performed. Given the considerations of access and cost, as well as the availability of portable devices, the American Sleep Disorders Association (now the American Association of Sleep Medicine [AASM]) published initial practice parameters regarding the use of PM devices in the assessment of OSA in The society classified sleep apnea evaluation studies based on the number of channels or signals that the monitor employed, categorized from type 1 to type 4. A minimum of 6 h of recording time was recommended when using any of the configurations. Types of Monitors Type 1 monitoring consists of full overnight polysomnography, with a minimum of two channels each for EEG, chin electromyogram, electrooculogram, as well as respiratory airflow (with thermistor or pressure-flow transducer), respiratory effort (thoracic and abdominal breathing movements), oximetry, and ECG or heart rate monitoring. These studies are fully attended by a technologist and are typically conducted in a sleep center. Portable studies (types 2 to 4) are summarized as follows: type 2 consists of an equivalent number of channels as type 1, with the singular difference being that the study is not attended by a technician. Type 3 utilizes at least four channels, including two channels for respiration and one channel for cardiac monitoring. Type 4 is made up of only one or two channels, typically including oxygen saturation or airflow. 18 At the time of the 1994 American Sleep Disorders Association practice parameters, the published literature was relatively scant and PM devices were deemed to have inadequate sensitivity for routine diagnostic use. Published cost-effectiveness data comparing PM devices to in-laboratory polysomnography were also not available. Between 1994 and 2003, several other systematic reviews regarding the use of PM devices were performed by various organizations. These included a second review by the AASM, 19 as well as non sleep-related organizations such as the Agency for Health Care Quality and Research 20 and the Emergency Care Research Institute. 21 These reviews continued to find lack of standardization, significant variability in scoring, and CHEST / 132 / 5/ NOVEMBER,

3 a lack of validation studies. Most recently, the AASM, along with the American College of Chest Physicians (ACCP) and American Thoracic Society (ATS) performed an exhaustive review of the literature regarding PM devices in a joint effort to establish practice parameters for all three societies. These practice parameters were published in 2003, with the review by Flemons and colleagues 22 providing their evidence-based underpinnings. Literature Review Flemons and colleagues 22 examined 51 studies, covering each type of PM and the level of evidence supporting their use. Each study was assigned a level of evidence score. The primary end point examined was the ability of PM devices to confirm or rule out disease. For many studies, the reviewers generated likelihood ratios as well as sensitivity and specificity values. Reproducibility, cost, failure rates, and generalizability were also examined in the review as secondary end points. Based on evidence from the systematic review, the three societies were not able to recommend unattended PM device use of any type for most patients with suspected OSA. 18 For type 2 devices, the tri-society practice parameters cited a lack of validated studies of adequate quality, as well as a lack of sensitivity and specificity data. Only one study 23 reported sensitivity and specificity data in the unattended setting, but it was of relatively poor quality and carried with it a 15% false-negative rate. Moreover, some type 2 monitors had data loss rates up to 20%. 23 The use of type 3 monitors in the unattended setting was not recommended due to several factors, including high rates of false-negative results. 18,22 Additionally, data loss was found to be as much as 18%, 24 and more than a third of patients enrolled in unattended type 3 PM studies had inconclusive results, requiring further investigation with an inlaboratory polysomnography. 25,26 Similar limitations also prevented the tri-society group from advocating the use of type 4 monitors. For example, Gyulay and colleagues 27 found that they were only able to classify 50% of their patients accurately using a type 4 device. In addition to these specific recommendations regarding types of monitor devices, the AASM/ ACCP/ATS also did not recommend the adoption of PM devices for initial screening without clearly establishing a pretest probability of disease. Moreover, the use of PM devices was not advocated in patients with comorbid conditions such as heart failure, chronic obstructive lung disease, obesity hypoventilation syndrome, and stroke. 18 The AASM guidelines 18 did allow for the use of PM devices under certain conditions. These include the lack of available polysomnography for patients with severe clinical symptoms consistent with OSA, the inability of the patient to be studied in the laboratory, or to evaluate response to therapy in a patient who has already undergone traditional inlaboratory polysomnography. Since the AASM revised guidelines were issued, several newer studies have been conducted using various PM devices in an effort to increase the existing pool of validity data. Using the Sleep Heart Health Study (SHHS) methodology and technology, Iber and colleagues 28 recruited 76 participants from the general community to volunteer for recordings both in the laboratory and at home. Subjects were randomized with respect to recording order and were monitored with the same type 2 device used for the SHHS cohort (Compumedics; Abbotsford, Australia). Sixty-seven of 76 subjects had adequate recordings from both studies. Eight percent of all studies were uninterpretable. Since EEG channels were incorporated in their type 2 monitor, total sleep time and sleep architecture could be assessed. Both median sleep time and sleep efficiency were better at home than in the laboratory. Median RDI values from at-home recordings were no different than those found in the laboratory. However, patients with an RDI 20 were more likely to be found in the home setting, whereas those with an RDI 20 were more likely to be found in the laboratory. These differences could not be explained by recording quality or other confounding variables. Their resulting misclassification rate was approximately 22%. The authors note 28 that this may be expected from the known night-tonight variability of OSA. Indeed, night-to-night variability has ranged from as little as 10% in clinic populations 29 to approximately 20% within the SHHS itself. 30 Dingli and colleagues 31 assessed the diagnostic accuracy of a type 3 monitor (Embletta; Flaga; Reykjavik, Iceland). The study design consisted of simultaneous recording with the PM and traditional in-laboratory polysomnography, followed by an athome assessment with the same PM. While the in-laboratory RDI and home RDI recorded from the type 3 monitor demonstrated no difference, the AHI generated from the in-laboratory polysomnography was significantly different. The authors 31 therefore categorized patients based on the RDI as definite OSA (RDI 20), possible OSA (RDI, 10 to 20), or normal (RDI 10). With these cut points however, 18 of 61 subjects fell into the possible OSA category. Moreover, an additional 11 of 61 subjects had technically inadequate studies. Thus, a total of 29 of 61 patients would have required further study Topics in Practice Management

4 In an effort to expand the population in whom type 3 monitors have been validated, Quintana- Gallego and coworkers 32 studied 75 patients with stable heart failure (86% New York Heart Association class I or II) [Apnoescreen II; Erich Jaeger; Wuerzburg, Germany]. All patients underwent an in-laboratory polysomnography as well as an unattended at-home study using the type 3 device. Patients were randomized as to study order, and the mean interval between studies was 13.8 days. PM electrodes were placed by a technician visiting the patient, and only 8% of the home studies failed. Using AHI cut points of 5, 10, and 15, the authors 32 were able to generate diagnostic accuracies of 78.6%, 84%, and 80%, respectively. Su and colleagues 12 attempted to validate a type 3 monitor (SNAP; SNAP Laboratories International; Wheeling, IL) in the attended laboratory setting. Sixty patients in this study underwent simultaneous polysomnography and SNAP recordings. Polysomnography AHI was compared to the SNAP RDI and was found to have a Pearson correlation of 0.92, suggesting closely related measurements. However, these findings have yet to be duplicated in the unattended environment. Conversely, Liesching and coworkers 33 retrospectively reviewed data from 31 sleep clinic patients who had undergone an initial screening SNAP recording and subsequent inlaboratory polysomnography. The mean interval between the two studies was approximately 5 months. The SNAP RDI agreed with the polysomnography AHI in only 11 of 31 patients. In addition, more than a quarter of the patients found to have abnormal SNAP study results had normal polysomnography results. Pittman and colleagues tested a novel type 4 monitoring device (Watch PAT; Itamar Medical; Caesarea, Israel) against traditional in-laboratory polysomnography. 34 The Watch PAT is a wrist-worn device that collects peripheral arterial tonometry and oxygen saturation data, coupled with actigraphy. Twenty-nine patients underwent simultaneous assessment with in-laboratory polysomnography and Watch PAT devices, as well as unattended at-home assessments wearing the Watch PAT alone. No data loss occurred in the unattended studies. Agreement between the in-laboratory device data and in-laboratory polysomnography was good, with an interclass correlation coefficient of While this was a small study sponsored by the device manufacturer, it nevertheless demonstrated the feasibility of miniaturized, unintrusive monitoring devices and the reliability of their data. Cost-effectiveness of PM Devices Data regarding the cost-effectiveness in real-world use with PM devices is limited. Many authors 35 have simply listed the up-front costs associated with a particular portable monitoring device vs in-laboratory polysomnography at their particular center, without undertaking a formal cost analysis that includes attention to details such as costs of laboratory supplies, physical plant costs, and staffing costs. The few studies that have performed a more complete cost analysis using PMs have not specified the type of monitor used in their respective models. To date, there have been no head-to-head cost comparison studies between PM types. Chervin and associates 36 modeled the cost utility of these devices under a variety of conditions. The authors found that in-laboratory polysomnography maximized quality-adjusted life years at 5 years after initial assessment as compared to PM devices. This difference was due largely to the inability to accurately diagnose some cases using PM devices, therefore requiring repeated studies in the laboratory. More recent analysis comes from Reuveni and Tarasiuk, 37 who modeled the cost-effectiveness of at-home screening for OSA using PM devices in Israel. In their model, they estimated that 30% of patients evaluated by a PM device at home would have inconclusive results and require repeat testing and 5% would have significant data loss or study failure. Polysomnography was assumed to have 100% diagnostic ability and only 0.5% data loss or study failure. Under these conditions, the investigators found that unattended PM studies would in fact cost more overall than in-laboratory polysomnography. This was due to the observation that patients undergoing PM evaluation at home would require 40% more testing than those studied in the laboratory. While the study by Reuveni and Tarasiuk 37 does much to establish the feasibility of modeling costeffectiveness of PM devices, the assumptions underlying the model may not apply to US centers. The authors also do not specify the type of PM device used for their decision analysis because there may be significant differences in costs between PM type. Moreover, cost-effectiveness models have not yet compared PM-based studies directly to in-laboratory studies including employing a split-night protocol for those with severe sleep-disordered breathing. Given the emerging ascendency of split-night evaluations in the diagnosis of OSA, 15 this may be the more relevant comparison to make now. CHEST / 132 / 5/ NOVEMBER,

5 Coding and Reimbursement Status of PM Devices Current procedural terminology code is reserved for sleep studies that do not require sleep staging. Code is defined as Sleep study, simultaneous recording of ventilation, respiratory effort, ECG or heart rate, and oxygen saturation, unattended by a technologist 38 and is applicable for most studies done using PM devices. Centers performing studies using PM devices should use current procedural terminology code TC. Under the most recent Medicare definitions, 39 in order for a study to be eligible for payment, it must be performed in a dedicated sleep center and be attended. In addition, there must be a supervising physician who is responsible for the procedure, although his or her presence is not required during the test. 40 Therefore, Medicare currently does not reimburse for PM studies. However, some third-party payers, such as CIGNA (Philadelphia, PA) and Blue Cross of California (Thousand Oaks, CA), may cover PM studies under the specific conditions laid out by the AASM. 41,42 In addition, the Veterans Health Administration has also begun using PM devices in the diagnostic workup of patients referred to its sleep clinics. 6 Based on these exceptions, a request was made by the American Academy of Otolaryngology-Head and Neck Surgery to the Centers for Medicare and Medicaid Services (CMS) to reconsider its position on PM studies. 43 In response to this request, the CMS requested public commentary as part of its review. Individual stakeholders as well as the ACCP, ATS, and AASM separately coordinated rebuttal arguments to dissuade the CMS from altering its position at the present time, citing the lack of evidence for efficacy and cost-effectiveness previously noted in this review. 43 In contrast, a significant number of practitioners as well as organizations such as the National Sleep Foundation and Apria Healthcare (Lake Forest, CA) believe that the addition of reimbursement of PM studies as an alternative to in-laboratory polysomnography to the national coverage determination would benefit the diagnosis and management approaches to OSA. 43 A final decision by the CMS on this matter is pending until December 13, In the interim, providers should contact individual payers to determine reimbursement status. Many payers will cover these studies on a case-by-case or contractual basis, provided that AASM conditions are met and traditional polysomnography is not readily available. Conclusion As the need for more patients to undergo diagnostic evaluation for OSA has increased, so has the appeal of PM devices. Many different device manufacturers have introduced products to satisfy demand. This has spurred advances in device design and introduced novel approaches to establishing the diagnosis of OSA. However, it has also led to the availability of numerous devices with limited evidence. The majority of PM devices have only been validated in patients with high pretest probability, largely from sleep clinic samples. While the results from most PM devices have been shown to correlate very closely with in-laboratory polysomnography, some still misclassify patients. In addition, the study failure rate of PM devices is higher than that of in-laboratory polysomnography, requiring patients to undergo repeated investigations. Future studies should focus on validating devices in a variety of populations, including those with comorbid conditions. 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