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Do The Test Right – TECHNIQUE - Developed 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 ANALOGUE PINPRICK COMPARISON TEST
The Analogue Pinprick Comparison Test employs a simple verbal analogue scale to provide rapid relative quantification of subtle neural deficit.
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 which significantly improves test subtlety to promote earlier diagnosis of diabetic peripheral neuropathy - The ANALOGUE PINPRICK COMPARISON TEST. The virtue and practicality of this technique has already been ably demonstrated by an NIHR/MRC study in the clinical setting Stacey Fisher et al., Primary Care Diabetes, https://doi.org/10.1016/j.pcd.2024.10.003
RELATIVE QUANTIFICATION OF SUBTLE CUTANEOUS PINPRICK SENSATION DEFICIT IN THE RAPID CARE SETTING USING THE ANALOGUE PINPRICK COMPARISON TEST
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 a 'reference' area you know to be unaffected by pathology - for example the palmar aspect of a wrist is particularly good because it shares a comparable nerve density with that of the dorsal hallux - by making multiple light applications in a continuously repetitive, percussive action to establish an “average” for the patient. This averaging effect is due to the phenomenon known as 'wind-up' which generates a summated perception of the stimulus providing the applications are made at a frequency of more than 1 per second 5. Your patient will quickly appreciate this “control” is “normal” for them which you can nominate verbally as representing an arbitrary score of “five” out of 10.
Next you can move immediately to the region intended for scrutiny – in the case of assessing for DPN the dorsal hallux - and ask them to grade their response, again out of 10, compared to the “control/reference” area. This simple verbal comparison allows your patient to express, often very subtle, distinctions in perception in contrast to the crude "yes/no" responses permitted by a binary technique. This makes the test relatively quantitative 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 repeated application that reduces standard deviation that produces a more reliable picture by negating the risk of single applications missing randomly distributed receptors whilst averaging out the multiples. This "Relative Quantification" technique has been assessed in the NHS/NIHR study published in Primary Care Diabetes and cited above 13 and is now being applied in a longer term NHS study (ODIN), https://doi.org/10.1186/ISRCTN12860460 intended to address neuropathic progression over longer time periods. To see Instructions for Use please go to the Instructions for Use page.
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.
13. Stacey Fisher et al., Primary Care Diabetes, https://doi.org/10.1016/j.pcd.2024.10.003