FOR PATIENTS
Quantitative sensory testing, abbreviated as QST, is a simple and mostly non-painful test to assess how your sensory nervous system works. The sensory nervous system is the part of the nervous system (including peripheral nerve receptors, nerve fibers, spinal cord and brain) that has the task of “feeling” the world around us.
Signals from the periphery (for instance a cold stimulus to your hand) are received, transduced, and led through this pathway up to the brain, just like any electrical signaling.
In QST, a stimulus is offered and the patient gives feedback on how this stimulus was perceived. Stimuli used in QST can be thermal (warmth and cold), vibration, pressure, touch, and electrical stimuli. Medoc’s product line is comprised of devices that can produce warmth and cold, vibration, and pressure.
Procedure
For the warmth test, a thermode, which is a small metal contact plate, is attached to the skin. The thermode is initially at skin temperature. When the operator (which can be a doctor, nurse, neurophysiologist or another healthcare worker) is done explaining the test procedure, the stimulus is turned on via a computer and the thermode contact plate will start to slowly warm-up. The operator may want you to press a button or let him or her know when you have first felt the warmth. Cold is tested with the same thermode, but the thermode is cooled instead of heated. Vibration is tested with a small circular probe that will start to vibrate with ever-increasing or decreasing intensity. You will be asked to indicate when you first start feeling the vibration or when you stop feeling the vibration.
Through this principle, warmth, cold, and vibration may be tested. Your doctor may also decide to test pain thresholds. To test pain thresholds, the operator will probably ask you to indicate when the sensation (be it cold, warmth, or pressure) is first perceived as painful. As soon as you indicate this, the stimulus will stop immediately.
Why QST?
QST is widely used to test the integrity of function of small peripheral nerve fibers. QST can be helpful because it is a simple, mostly painless test that is non-invasive, and informative. With QST even small deficits of sensory nerve function can be detected early. QST can be used to follow patients with Diabetes, or to monitor peripheral nerve function with or without complaints of altered sensation or pain. It can also be used to track nerve function of patients suspected of, or diagnosed with peripheral neuropathy, or other nervous system or pain disorders.
QST in your country
Clinical QST use is quite established in some countries, and much less so in other countries. The reasons for this are mostly dependent on the healthcare system in your country and your own doctor’s preferences. To find our more, ask your neurologist, endocrinologist or pain physician about it.