1. Aetna considers quantitative sensory testing (QST) experimental and investigational for the evaluation of musculoskeletal pain, the management of individuals with neuropathy, prediction of the response to opioid treatment, or any other diagnoses because its diagnostic value has not been established.

2. Aetna considers current perception threshold (CPT) testing experimental and investigational because the effectiveness and clinical applicability of this testing in diagnosing and/or managing diabetic peripheral neuropathy or other diseases has not been established.

3. Aetna considers voltage-actuated sensory nerve conduction threshold (VsNCT) testing experimental and investigational because its clinical value has not been established in the peer-reviewed published medical literature.

Quantitative sensory testings (QSTs) are techniques employed to measure the intensity of stimuli needed to produce specific sensory perceptions.  They are used to evaluate a sensory detection threshold or other sensory responses from supra-threshold stimulation.  The common physical stimuli are (i) touch-pressure, (ii) vibration, and (iii) coolness, warmth, cold pain, and heat pain.  In QST, the subject must be able to comprehend what is being asked by the test, alert and not taking mind-altering medications, and not biased to a certain test outcome.

Abnormal or elevated QST measurements are not specific in the diagnosis of any particular type of neuropathy, and in fact do not necessarily indicate any form of peripheral neuropathy.  There are no prospective clinical studies demonstrating that quantitative tests of sensation improve the management and clinical outcomes of patients over standard qualitative methods of sensory testing.

The vibrometer is a device used for measuring sensation/sensitivity to vibration.  Testing of vibration sense can be adequately performed with a tuning fork of 128 Hz.

The American Academy of Neurology evaluated the clinical utility, efficacy, and safety of QST (Shy et al, 2003).  The authors concluded that QST is a potentially useful tool for measuring sensory impairment for clinical and research studies.  However, QST results should not be the sole criteria used to diagnose pathology.  Because malingering and other non-organic factors can influence the test results, QST is not currently useful for the purpose of resolving medicolegal matters.  The authors stated that well-designed studies comparing different QST devices and methodologies are needed and should include patients with abnormalities detected solely by QST.

The American Association of Electrodiagnostic Medicine (Chong and Cros, 2004) stated that available literature data do not allow conclusions regarding the relative merits of individual QST instruments.

Eisenberg and colleagues (2010) used both static and dynamic QST on 40 healthy volunteers in order to examine if this methodology can predict the analgesic effects of oral oxycodone, as compared to a placebo, on latency to onset, pain intensity, and tolerance to the cold pressor test.  Static QST consisted of measuring heat and cold pain thresholds.  Dynamic QST included measurements of the magnitude of the diffuse noxious inhibitory control (DNIC)-like effect and of temporal summation (TS).  Results showed that oxycodone, but not the placebo, significantly elevated the latency and tolerance to cold pain and significantly reduced pain intensity.  The static QST results showed that heat pain thresholds predicted the magnitude of reduction in pain intensity in response to oxycodone treatment (F((1,22)) = 5.63, p = 0.027, R(2) = 0.17).  The dynamic QST results showed that TS predicted the effect of oxycodone on the tolerance to cold pressor test (F((1,38)) = 9.11, p = 0.005, R(2) = 0.17).  These results suggested that both static and dynamic QST have the potential to be useful in the prediction of the response to opioid treatment.  The findings of this study need to be validated especially in patients with addiction.

Pavlakovic and Petzke (2010) noted that QST is a non-invasive method of assessing sensory and pain perception that has been used in the past 30 years primarily for analysis of cutaneous and mucosal perception.  In recent years, several published studies have demonstrated that QST may be useful in the analysis of painful musculo-skeletal disorders as well.  Based on the results of these studies, it can be postulated that QST may be useful in the analysis of the pathogenesis, classification, and differential diagnosis of musculo-skeletal disorders.  However, due to the diverse ethiopathogenetic basis of these disorders, a broad range of QST test batteries may be necessary to analyze the various musculo-skeletal disease entities.  These researchers analyzed published studies on this subject and summarized current information on altered sensory and pain perception available for some of the most common musculo-skeletal disorders.  The authors concluded that at present, QST remains primarily a research tool but may be useful in differential diagnosis in indicating the presence of central sensitization and for clinical monitoring of disease progression or treatment response.

In a review on the usefulness and limitations of QST in neuropathic pain states, Hansson et al (2007) stated that there is a lack of specificity of current QST databases; thus QST can not be used alone for diagnosis of a neurological lesion.  The authors also noted that QST is not useful in predicting which patients with post-herpetic neuralgia (PHN) or peripheral neuropathy would benefit from lidocaine patches.  Also, serial QST evaluations in patients with acute herpes zoster failed to predict who would develop PHN.  Furthermore, the authors stated that the expected role of QST in the definition of a mechanisms-based approach to neuropathic pain has not yet been met.

Current perception threshold (CPT) testing (also known as sensory nerve conduction threshold testing) entails the quantification of the sensory threshold to transcutaneous electrical stimulation.  It has been used to examine sensory nerves.  In general, CPT testing falls into the general category of QST.  CPT testing has been studied for a wide range of clinical applications such as evaluation of peripheral neuropathies, detection of carpal tunnel syndrome, spinal radiculopathy, evaluation of the effectiveness of peripheral nerve blocks, quantification of hypoesthetic and hyperesthetic conditions and differentiation of psychogenic from neurological disorders.  The AXON-II NCSs System (PainDx, Inc., Laguna Beach, CA), Neurometer® Current Perception Threshold (Neurotron, Inc., Baltimore, MD) and the Medi-Dx 7000™ (Neuro Diagnostic Associates, Inc., Laguna Beach, CA) are devices cleared by the Food and Drug Administration (FDA) through the 510k process for the use of measuring the threshold for sensory nerve conduction. Thus, the manufacturers were not required to present evidence of efficacy to support a premarket approval application (PMA). These devices have been used to detect metabolic, toxic, acquired, hereditary, compression, traumatic, and other peripheral neuropathies as well as sensory impairments resulting from central nervous system pathology.  However, the effectiveness and clinical applicability of CPT testing in diagnosing and/or managing a disease has not been established.

A study by Tack et al (1994) compared CPT testing at different frequencies with standardized clinical examination scores.  The authors concluded that CPT testing “seemed rather insensitive at detecting neuropathy”.  Compared with standard clinical examination, CPT testing “is only of limited value, mainly because of high variability and poor reproducibility”.

Yilmaz et al (2010) compared sensory thresholds in different nerve-fiber types in men with chronic pelvic pain syndrome (CPPS) and healthy controls, using thermal sensory testing and measuring CPT.  These researchers enrolled 22 men with CPPS and 20 healthy control participants.  They determined the thermal sensory perception thresholds of C and Adelta nerve fibers on the perineum and left posterior thigh.  To test CPT, they used sine wave electrical stimulation at 5-Hz, 250-Hz, and 2,000-Hz, resulting in the selective depolarization of small unmyelinated C fibers, small myelinated Adelta, and large myelinated Abeta fibers, respectively.  These researchers bilaterally tested the hypothenar surface of the palms, medial parts of soles, mid-shaft of penis, and 1 site in the mid-perineum, for a total of 7 sites.  The mean age of men with CPPS was similar to that of controls [42.8 (standard deviation, 9.4) and 40.4 (standard deviation, 13.2) years, respectively, p = 0.548].  There was no significant difference between the 2 groups for thermal perception thresholds in both the perineum and left thigh (p > 0.05).  There was also no difference between the 2 groups for CPT values of all 3 frequencies of stimuli in each area tested (p > 0.05 for all comparisons).  The authors concluded that the absence of sensory threshold differences between men with CPPS and controls, with either thermal stimulation of C and Adelta fiber afferents or electrical stimulation of C, Adelta, and Abeta fiber afferents, discounts the existence of a peripheral neuropathy as a cause for pain in men with CPPS.

Liao et al (2010) recruited 49 patients with classical trigeminal neuralgia (TN) according to the latest guidelines of the International Classification of Headache Disorders, and divided them into an acute (less than or equal to 30 days onset; n = 13) and a chronic (greater than 30 days onset; n = 36) group.  These investigators used blink reflex study and CPT testing to evaluate the painful facial areas and contralateral non-painful areas of patients with classical TN.  Current perception threshold 5-Hz examinations, which correlate with unmyelinated fiber function, showed significantly decreased CPTs in the acute stage (11.62 +/- 6.99 versus 18.69 +/- 9.66, p = 0.025), but significantly increased CPTs in the chronic stage (26.67 +/- 18.65 versus 19.69 +/- 13.70, p = 0.010) on the painful side when compared with the contralateral non-painful side.  However, CPTs at 250-Hz (Adelta) and 2,000-Hz (Abeta) examinations did not show significant differences between the painful and non-painful sides.  In contrast, only 3 (3/49) patients showed an abnormal trigeminal nerve stimulation on the ipsilateral painful side by blink reflex study.

An assessment on the use of electroneurometer in the diagnosis of carpal tunnel syndrome (CTS) conducted by the American Association of Electrodiagnostic Medicine (David et al, 2003) reached the following conclusions: "It is the opinion of the American Association of Electrodiagnostic Medicine (AAEM) that all of the literature reviewed and describing the nervepace digital electroneurometer (NDE) and neurosentinel (NS) are flawed.  Limb temperature, which affects the speed of nerve conduction, was controlled in only one study.  In most reports, reference populations were not studied to provide a scientifically based source for control values.  Standard statistical measures of latency values (mean, standard deviation, and range) were not specified in most reports.  Moreover, most studies comparing NDE and NS to standard nerve conduction studies (NCSs) make an incorrect assumption: that distal motor latency or an isolated digital sensory latency values are sensitive measures for diagnosing median nerve entrapment at the wrist.  In fact, detailed sensory NCSs, including segmental stimulation across the palm-to-wrist segment or in comparison to adjacent sensory nerves, is by far the more sensitive technique in this regard and is probably the earliest finding in median nerve entrapment at the wrist.  It is the opinion of the AAEM that the NDE, as well as the newer NS, are experimental and are not effective substitutes for standard electrodiagnostic studies in clinical evaluation of patients with suspected CTS."

The Medi-Dx 7000™ (Neuro Diagnostic Associates) is a voltage-actuated sensory nerve conduction test (VsNCT) device.  The device was cleared by the FDA based on a 510(k) application.  An updated version of the Medi-DX 7000 is the Neural-Scan™ (Neuro Diagnostic Associates, Inc.), which is a current potential threshold test with a potentiometer.  The V-sNCT measures the voltage amplitude necessary to cause a discernable nerve impulse.  VsNCT results are adjusted and compared to population means.  The most severe hypoesthesia is considered the primary lesion.  There is no peer-reviewed published medical literature on the use of voltage-actuated sensory nerve conduction tests and their impact on clinical outcomes.

In March 2004, the Center for Medicare and Medicaid Services (CMS) re-affirmed its non-coverage policy on the CPT and sensory nerve conduction threshold test (sNCT); CMS (2004) concluded that “there continues to be insufficient scientific or clinical evidence to consider the sNCT test and the device used in performing this test as reasonable and necessary”.

A study by Cork, et al. (2002) reports on the performance characteristics of vSNCT using the Medi-Dx 7000 and physical examination findings for predicting nerve root pathology on an epidurogram. The study has a number of flaws, in particular lack of blinding, and does not report on improvements in clinical outcomes with use of vSNCT. It should be noted that the study was published in a journal that not indexed by the National Library of Medicine in the PubMed database of peer-reviewed published medical literature.

In addition, it should be noted that CPT code 95904 is not the correct code to bill for V-SNCT. CPT code 0110T (“Quantitative sensory testing (QST), testing and interpretation per extremity; using other stimuli to assess sensation”) or G0255 (“Current perception threshold/sensory nerve conduction test, (SNCT) per limb, any nerve”) should be used to bill for this service.