Dr Vinaya guides you on the basics of Sensitometer HCP.
The loss of nerve fibre in neuropathy (nerve disease or damage) is neither uniform nor simultaneous. The damage to nerve fibres results in diminishing thermal (hot), cold and pain sensation and disrupts signals between the brain and portions of the autonomic nervous system leading to an autonomic decline.
Sensitometer HCP (Hot, Cold, Pain) helps detect diabetic polyneuropathy (damage or disease affecting peripheral nerves) at an early stage. This is done by detecting any change in tolerance to heat and cold perception in the foot. Sensitometer HCP is used to detect Heat Cold and associated Pain perception thresholds.
Response is expected around 36 + 2 degrees centigrade when the probe appears warm. The sensation of heat pain or a pricking sensation without a component of warmth may be experienced from 42 to 45 degrees Celsius.
The readings are interpreted as follows:
- Neutral zone: 32 to 34 degrees Celsius
- Cool Detection threshold: 29 to 32 degrees Celsius (just below neutral zone).
- Warm Detection threshold: 35 to 38 degrees Celsius (above neutral zone)
- Heat Pain Detection threshold: 42 to 45 degrees Celsius
- Cold Pain Detection threshold: below 27 down to 27 degrees Celsius
Lack of warm, heat or cold perception is indicative of nerve fibre damage or disease.
Though it is reliable, it is not a diagnostic tool for Diabetes.
Performing the test
The circular metal probe is placed on the base of the feet at particular points.
- Testing cold Perception threshold
Patient should respond when the sensation of coolness is felt. This will happen before 29 degrees Celsius in normal patients. The point at which one senses the Coolness is Cool Perception threshold.
On further pressing the Cool Button the temperature will continue to drop and at about 27 to 23 degrees Celsius. The patient will feel slight discomfort. This point is the cold pain point. (This is not a cold tolerance test; it is the beginning of discomfort.)
- Testing Warm Perception threshold
It is exact reciprocal of the Cool Perception threshold. Instead of a cool button, press the warm button once and the temperature will increase to 30 degrees Celsius. The temperature will start rising at the rate of 1 Degree Celsius per four seconds.
Note: The response time is 1.5 to 2 seconds and the rate of rise of temperature is 1 degree Celsius. Therefore the threshold may be 1.5 to 2 degrees Celsius higher than actual.
- Sensitometer HCP helps detecting diabetic polyneuropathy at an early stage.
- Non-invasive testing
- All people with Diabetes can be tested using Sensitometer HCP.
- A simple and highly reliable instrument, to measure the Thermal Perception Thresholds in suspected or known neuropathy.
- Testing in air-conditioned rooms may distort reading.
Dr Vinaya is an internationally renowned podiatrist from Bengaluru.