Do The Test Right – TECHNIQUE - Modified For Greater Specificity
Simply Compare Sensation Scores Out of ‘10’ Between Areas of ‘Normal’ Control and Potential Deficit Using Multiple Applications
TECHNIQUE IS PIVOTAL
The current standard, evidence based clinical test procedure recommended by the American Diabetes Association is published as follows:
“A disposable pin should be applied just proximal to (before) the toenail on the dorsal (upper) surface of the hallux, (great toe) with just enough pressure to deform the skin. Inability to perceive pinprick over either hallux would be regarded as an abnormal test result”. (Extract from: Comprehensive Foot Examination and Risk Assessment: A report of the Task Force of the Foot Care Interest Group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists, Diabetes Care August 2008 vol. 31 no. 8 1679- 1685, p1681) http://care.diabetesjournals.org
However, a more sophisticated technical adaptation is available that will significantly improve test subtlety.
Everyone’s perception is idiosyncratic and state dependent. Attempting to impose a standardized neuropathy threshold of stimulation across the population, even with a device that imparts a predictable level of force, simply won't work 4. Therefore by employing the second rule of clinical examination - comparison - we can we detect subtle degrees of deficit rather than just a threshold driven “yes or no” picture by utilising a verbal analogue scale. Use a Medipin to establish “Normal” sensation in an area you know to be unaffected by pathology - for example the palmar aspect of a wrist is particularly good or tip of a shoulder - by making multiple light applications in a continuously repetitive, percussive action to establish an “average” for the patient 5 – this represents the “control”. Whilst doing so you can tell your patient that this is “normal” for them.
You can grade their responses by setting the “normal” control area at an arbitrary score of “five” out of 10 allowing them to offer a specific comparative value in another area. Immediately move to the region under suspicion – for example the dorsal halux - and ask them how the score compares to the control. This makes the test quantitative rather than the binary interpretation provided by the “yes or no” response and you can easily move back and forth between the test areas to help refine their response 6-7. It really works - patients are very good with verbal and visual analogue pain scales for expressing subtle differences in either direction – either hypo or hyperaesthetic 8-12. Remember; each application is imperfect and it is the continuous application that reduces the standard deviation and produces a more reliable picture by negates missing out randomly distributed receptors and averaging out application pressure. See “Instructions” below:
4. A.T. Shirgaonkar, M. Purva, I.F. Russell; A double blind comparison of the variability of block levels assessed using a hand help Neurotip™ or a Neuropen® at elective caesarean section under spinal anaesthesia. International Journal of Obstetric Anesthesia (2010) 19, 61–66
5. Herrero JF, Laird 2000, JMA, Lopez-Garcia JA. Wind-up of spinal cord neurones and pain sensation: much ado about something? Prog Neurobiol ;61:169–203
6. Jeng C, Michelson J, Mizel M. Sensory thresholds of normal human feet. Foot Ankle Int. 2000;21:501-504.
7. Rolke R, et al. Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): Standardized protocoland reference values. Pain 123 (2006) 231–243
8. Wallerstein SL (1984.) Scaling clinical pain and pain relief. In: Bromm B, ed. Pain measurement in man: neurophysiological correlates of pain. New York: Elsevier
9. Kelly AM (1998). Does the clinically significant difference in VAS pain score differ with age, gender or cause of pain? Acad Emerg Med;5:1086–90.
10. Collins SL, Moore RA, McQuay HJ (1997). The visual analogue pain intensity scale: What is moderate pain in millimetres? Pain;72:95–7.
11. Scott J, Huskisson EC (1976). Graphic representation of pain. Pain;2:175–84.
12. Menegazzi J. (1996 ) Measuring pain at baseline and over time. Ann Emerg Med;27:433–5.