Quantitative Sudomotor Axon Reflex Test

What is it?

The quantitative sudomotor axon reflex test (QSART) is used to assess the small nerve fibers, which are linked to the sweat glands.

Why do it?

QSART is used to diagnose:

  • Painful, small fiber neuropathy when nerve conduction test results are normal
  • Disturbances of the autonomic nervous system, which controls the sweat glands, heart, digestive system, other organs, and blood pressure
  • Complex pain disorders

How is it performed?

The test has three parts and measures resting skin temperature, resting sweat output, and stimulated sweat output. Measurements are typically taken on arms, legs or both. A small plastic cup is placed on the skin and the temperature and amounts of sweat under the skin are measured. To stimulate sweat a chemical is delivered electrically through the skin to a sweat gland, but the patient will only feel warmth. A computer is used to analyze the data to determine how well the nerves and sweat glands are functioning.

How will it feel?

The patient will experience little or no discomfort, but the test could take two or three hours to complete.

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