Quantitative Sensory Testing
DESCRIPTION
Quantitative sensory testing (QST) systems have been investigated for the noninvasive assessment and quantification of sensory nerve function in patients with symptoms of, or the potential for, neurologic damage or disease. Pain conditions evaluated may include diabetic neuropathy and uremic and toxic neuropathies, complex regional pain syndrome, carpal tunnel syndrome, and other nerve entrapment/compression disorders or damage.
QST systems measure and quantify the amount of physical stimuli required for sensory perception to occur in the patient. As sensory deficits increase, the perception threshold of QST will increase, which may be informative in documenting progression of neurologic damage or disease. QST has not been established for use as a sole tool for diagnosis and management, but has been used in conjunction with standard evaluation and management procedures (e.g., physical and neurological examination, monofilament testing, pinprick, grip and pinch strength, Tinel, Phalen and Roos sign) to enhance the diagnosis and treatment planning process and confirm physical findings with quantifiable data. Stimuli used in QST includes touch, pressure, pain, thermal (warm and cold), or vibratory stimuli.
The gold standard for evaluation of myelinated large fibers is the electromyographic nerve conduction study (EMG-NCS). However, the function of smaller myelinated and unmyelinated sensory nerves, which may show pathologic changes before the involvement of the motor nerves, cannot be detected by nerve conduction studies. Small fiber neuropathy has traditionally been a diagnosis of exclusion in patients who have symptoms of distal neuropathy and a negative nerve conduction study. Depending on the type of stimuli used, QST is proposed to assess both small and large fiber dysfunction. Touch and vibration measure the function of large myelinated A alpha and A beta sensory fibers. Thermal stimuli are used to evaluate pathology of small myelinated and unmyelinated nerve fibers. The Vibration Perception Threshold (VPT) meter (Xilas Medical) received U.S. Food and Drug Administration (FDA) 510(k) marketing clearance in 2003 (K030829). The CASE IV Computer Aided Sensory Evaluator (WR Medical Electronics, Stillwater, MN) received FDA 510(k) marketing clearance in 1992 (K910624); CASE IV measures vibration or thermal thresholds.
Pressure-specified sensory devices (PSSD) assess large myelinated sensory nerve function by quantifying the thresholds of pressure detected with light, static, and moving touch. The Nk Pressure-Specified Sensory Device™ (Nk Biotechnical Engineering) consists of 1 or 2 blunt probes and sensitive transducers to measure and record the perception thresholds of pressure on the surface of the body in grams per square millimeter. The device has been investigated as an aid in the diagnosis and assessment of nerve function, including diabetic peripheral neuropathy, carpal tunnel syndrome, and other nerve entrapment or compression syndromes, and postoperative assessment of sensory outcomes after liposuction, breast reduction mammaplasty, etc. The Nk Pressure-Specified Sensory Device™ received FDA 510(k) marketing clearance in 1994 (K934368).
Another type of sensory nerve conduction threshold test is current perception threshold testing, which involves the quantification of the sensory threshold to transcutaneous electrical stimulation. In current perception threshold testing, typically 3 different frequencies are tested: 5 Hz, designed to assess C fibers; 250 Hz, designed to assess A-delta fibers; and 2,000 Hz, designed to assess A-beta fibers. Results are compared with those of a reference population. The Neurometer® Current Perception Threshold (Neurotron, Inc) and the Medi-Dx 7000® (Neuro Diagnostic Associates) are two devices with 510(k) marketing clearance from the FDA for the use of measuring the threshold for sensory nerve conduction. Updated versions of the Medi-DX7000 are the Neural-Scan™ (Neuro Diagnostic Associates) and the AXON II® (PainDx), which are designed to quantitatively measure sensory threshold to transcutaneous electrical stimulation. These devices may include a device known as the potentiometer.
Because QST combines the objective physical sensory stimuli with the subjective patient response, it is psychophysical in nature and requires patients who are alert, able to follow directions, and cooperative. Psychophysical tests have greater inherent variability, making their results more difficult to standardize and reproduce.
POLICY
IMPORTANT REMINDERS
ADDITIONAL INFORMATION
Published studies are insufficient at demonstrating that evaluation by quantitative sensory testing can predict clinical events and, thus, be used to alter the treatment of individuals.
SOURCES
BlueCross BlueShield Association. Medical Policy Reference Manual. (6:2012). Quantitative sensory testing (2.01.39). Retrieved September 26, 2012 from BlueWeb. (19 articles and/or guidelines reviewed)
Centers for Medicare & Medicaid Services. Medicare Coverage Database. (2012, July). Sensory nerve conduction threshold tests (sNCTs) (160.23). Retrieved October3, 2012 from Ingenix.
Cruccu, G., Sommer, C., Anand, P., Attal, N., Garcia-Larrea, L., Haanpaa, M. (2010). EFNS guidelines on neuropathic pain assessment; revised 2009. European Journal of Neurology, 17 (8), 1010-1018.
Mythili, A., Dileep - Kumar, K., Subrahmanyam, A., Venkateswarlu, K., & Butchi, R. (2010). A comparative study of examination scores and quantitative sensory testing in diagnosis of diabetic polyneuropathy. International Journal of Diabetes, 30 (1), 43-48. (Level 3 Evidence - Independent)
Shy, M. E., Frohman, E. M., So, Y. T., Arezzo, J. C., Cornblath, D. R., Giuliani, M. J., et al. (2003). Quantitative sensory testing: Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (Reaffirmed - November 15, 2008). Neurology, 60 (6), 898-904.
U. S. Food and Drug Administration. (2009, January). Center for Devices and Radiological Health. 510k Pre-market Notification Database. K072882. Retrieved January 14, 2011 from http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=26108.
U. S. Food and Drug Administration. (1998, May). Center for Devices and Radiological Health. 510k Pre-market Notification Database. K980866. Retrieved October 3, 2012 from http://www.accessdata.fda.gov/cdrh_docs/pdf/K980866.pdf.
Winifred S. Hayes, Inc. Medical Technology Directory. (2010, February). Epidermal nerve fiber density test for diagnosing neuropathy. Retrieved October 3, 2012 from www.Hayesinc.com/subscribers (66 articles and/or guidelines reviewed)
ORIGINAL EFFECTIVE DATE: 1/14/2006
MOST RECENT REVIEW DATE: 11/8/2012
ID_BA
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