The use of the Nervespace Digital Electroneurometer, the Neurometer CPT,  the Pressure-Specifying Sensory Device (PSSD), or any similar device, does not meet member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness in improving health outcomes.

 

For contracts without primary coverage criteria, the use of the Nervespace Digital Electroneurometer, the Neurometer CPT, the Pressure-Specifying Sensory Device (PSSD), or any similar device  is considered investigational.  Investigational services are an exclusion in the member certificate of coverage.

Quantitative sensory testing (QST) can either be used as the initial diagnostic test or as a monitoring test in patients to assess ongoing sensory deficits. The type of data required to validate QST in these 2 different settings are different. For example, as an initial diagnostic test, one would like to see standard measures of diagnostic performance, such as sensitivity, specificity, positive and negative predictive values as compared to conventional tests, such as monofilament testing, pinprick, etc. In some cases, QST has been proposed as an alternative to nerve conduction studies, and, in this setting, one would like to compare the diagnostic performances of these 2 tests. When used as a monitoring technique, test/retest reliability is an important outcome, as well as defining a clinically significant change in sensory perception. As with any diagnostic test, it is important to evaluate how the results of the test will be used to enhance patient management, either in terms of instituting more prompt or more effective therapy, or in the avoidance of more invasive tests, such as nerve conduction studies.

 

In a 2003 report, the American Academy of Neurology (AAN) noted QST should not be used as a sole method for diagnosis of pathology.  The AAN indicated QST poses technical challenges in the methodology of testing, reproducibility, and psychophysical factors that limit the objectivity of testing results. Siao and Cros noted in a review that QST is influenced by many extraneous factors and may be subject to misinterpretation and misuse.  In addition, normal reference levels do not exist, and the reproducibility of QST has not been firmly established. Also, there are no generally recognized standards for QST techniques, performance, and interpretation.

 

Current Perception Threshold Testing

 

In 1999, the American Association of Electrodiagnostic Medicine (AAEM) published a technology review of the Neurometer® device.  This evaluation suggested the following criteria for the evaluation of the device:

 

The AAEM assessment concluded that there is inadequate scientific literature meeting the above criteria to validate the clinical role of current perception threshold testing. Much of the literature compares the results of Neurometer® testing to nerve conduction studies in patients with known disease. In many instances the results of the Neurometer® testing demonstrated more numerous or pronounced abnormalities compared to nerve conduction studies, which was consistent with the hypothesis that abnormalities of small nerve fibers precede those of large nerve fibers tested in nerve conduction studies. However, this observation could also be related to the fact that use of the Neurometer® involves testing at multiple sites with 3 different frequencies and that any identified abnormality is considered significant. Testing the perception threshold at different frequencies is designed to evaluate the function of different subclasses of nerve fibers. However, this hypothesis has not been adequately evaluated, in part due to a lack of a diagnostic gold standard for comparison purposes. In this situation, validation of a diagnostic technology requires study of how the technique is used in the management of the patient and whether subsequent changes in the management of the patient are associated with improved health outcomes. Finally, results of the Neurometer® testing are compared to a normal reference population. The review by the AAEM found that the source of the normal values was not apparent from the published literature. The AAEM assessment concluded with the following recommendations regarding research to validate the clinical utility of the Neurometer®:

 

In an updated review of the literature, 2 studies reported on attempts to establish the diagnostic utility of current perception threshold testing. In Yamashita, 48 patients with lumbar radiculopathy were compared with 11 healthy controls to evaluate current perception thresholds using the Neurometer®.  The authors reported finding significantly higher current perception threshold values in the affected legs of patients with lumbar radiculopathy at 2000, 250, and 5 Hz frequencies than in the unaffected legs. Current perception threshold values in the affected legs were also significantly higher in control subjects at 2000 and 250 Hz frequencies but not significantly different at 5 Hz. The authors concluded that current perception threshold testing may be useful in quantifying sensory nerve dysfunction in patients with radiculopathy. However, there was no discussion of how this quantification could be used in the management of the patient.

 

Park and colleagues attempted to validate current perception threshold testing against the gold standard references for thermal sensory testing and von Frey tactile hair stimulation in a randomized, double-blind, placebo-controlled trial on 19 healthy volunteers. The authors reported finding that all current perception threshold measurements showed a higher degree of variability than thermal sensory testing and von Frey measurements, but concluded that there is some evidence that similar fiber tracts may be measured, especially C-fiber tract activity at 5 Hz, with current perception threshold, thermal sensory, and von Frey testing methods. However, none of these studies sufficiently address the AAEM recommendations for research to validate the clinical utility of current perception threshold testing.

 

A review of the literature on pressure-specified sensory device (PSSD) testing found insufficient evidence to demonstrate that PSSD testing will provide any further information than what can ordinarily be determined during standard evaluation and management of patients with potential nerve compression, disease, or damage. Standard evaluation and management consist of physical examination techniques and may include Semmes-Weinstein monofilament testing and, in some more complex cases, NCV testing. While PSSD may be a useful adjunct in neurosensory testing, no clinical trials were identified that demonstrated that use of the PSSD resulted in earlier and/or more accurate diagnoses of nerve damage and improved patient outcomes. Nor were any studies found that examined this technology for patient selection criteria for carpal or tarsal tunnel release, plexus neurolysis, etc. In addition, no clinical practice guidelines were found that addressed the use of PSSD. As noted here, in the evaluation of current perception threshold testing, further research is needed to validate the clinical utility of PSSD; to establish reference values for well-characterized and representative populations; to establish normal values in control subjects and patients with specific diseases to reduce interoperator variability and increase reproducibility; and to establish sensitivity and specificity comparisons to appropriate standards.

 

A literature review was conducted for the period of March 2005 through July 2006. No clinical studies were found that would alter the policy statement noted above. While studies using these technologies continue, the impact of this testing on improving clinical outcomes has not been shown. There also continues to be questions about the performance of the test; one recent study noted “significant” variability in thermal perception thresholds during a 1-hour time in 24 female volunteers.

 

A search of the MEDLINE database was performed for the period of August 2006 through February 2008. A multicenter study funded by a pharmaceutical company compared vibration threshold testing (CASE IV, biothesiometer, C64 graduated tuning fork) with standard nerve conduction studies (NCS) in 195 (86% follow-up) subjects with diabetes mellitus. The tests were performed independently by trained technicians; all NCS evaluations were sent to a central reading center. Intra-class correlation coefficients for the tests ranged from 0.81 to 0.95, indicating excellent to highly reproducible results. Correlation coefficients for the various vibration QST instruments were moderate at -0.55 (CASE IV vs. tuning fork) to 0.61 (CASE IV vs. biothesiometer). In contrast, the correlation coefficient between CASE IV and a composite score for nerve conduction was low (r = 0.24). These results indicate that vibration threshold testing could not replace NCS testing, but might provide a complementary outcome measure. Overall, questions remain about the clinical utility of sensory nerve conduction threshold testing. Evidence is insufficient to demonstrate an improvement in health outcomes. Therefore, the policy statement remains unchanged.

 

Physician Specialty Society and Academic Medical Center Input

 

In response to the request for input from Physician Specialty Societies and Academic Medical Centers, input was received through the American Academy of Neurology and one academic medical center regarding use of quantitative sensory testing while the policy was under review. Input from both sources agreed with the policy statement that QST is considered investigational, as adopted in the policy in April 2008.

 

A 2003 report from the American Academy of Neurology concluded that QST is probably (level B recommendation) an effective tool in the documentation of sensory abnormalities and in documenting changes in sensory thresholds in longitudinal evaluation of patients with diabetic neuropathy. Evidence was weak or insufficient to support the use of QST in patients with other conditions (small fiber sensory neuropathy, pain syndromes, toxic neuropathies, uremic neuropathy, acquired and inherited demyelinating neuropathies, or malingering). General recommendations indicated that QST results should not be the sole criterion used to diagnose structural pathology, or either a peripheral or central nervous system (CNS) origin. Abnormalities on QST must be interpreted in the context of a thorough neurologic examination and other appropriate testing, such as electromyography (EMG), nerve biopsy, skin biopsy, or appropriate imaging studies.

 

The American Association of Electrodiagnostic Medicine published a technology literature review on quantitative sensory testing (light touch, vibration, thermal, and pain) in 2004. The review concluded that QST is a reliable psychophysical test of large- and small-fiber sensory modalities, but is highly dependent on the full cooperation of the patient. Abnormalities do not localize dysfunction to the central or peripheral nervous system, and no algorithm can reliably distinguish between psychogenic and organic abnormalities. The AAEM technology review also indicated that QST has been shown to be reasonably reproducible over a period of days or weeks in normal subjects, but for individual patients, more studies are needed to determine the maximum allowable difference between 2 QSTs that can be attributed to experimental error.

 

In 2004 the European Federation of Neurological Societies published guidelines on neuropathic pain assessment. The task force concluded that QST is helpful to quantify the effects of treatments on allodynia and hyperalgesia (grade A recommendation), but recommends the use of simple tools such as a brush and high-threshold von Frey filaments. Because QST abnormalities are also found in non-neuropathic pains, QST abnormalities cannot be taken as a conclusive demonstration of neuropathic pain. The recommendations also indicated that QST is expensive and time consuming, and thus difficult to use in clinical practice.

 

 

 

  

 

 

 

 

 

A literature search conducted using the MEDLINE database through September 2017 did not reveal any new information that would prompt a change in the coverage statement.