Sudomotor Axon Reflex Test (QSART)

Quantitative Sudomotor Axon Reflex Test (QSART test) is a diagnostic test that measures the functioning of the sympathetic nervous system, specifically the sweat glands, which are controlled by the sympathetic nervous system. The test measures the amount of sweat produced in response to electrical stimulation of the skin.

QSART can help diagnose conditions such as autonomic neuropathy that control sweating, are damaged. The test can also be used to evaluate the effectiveness of treatment for conditions such as diabetic neuropathy and reflex sympathetic dystrophy.

How do you perform the Quantitative Sudomotor Axon Reflex Test?

A small electrical current is applied to the skin, which stimulates the sweat glands. The amount of sweat produced is then measured and recorded. The test is usually performed on the palms of the hands and soles of the feet.

See Also: Manual Muscle Testing

Performing a QSART involves the following steps:

1. Preparation: The patient should avoid using antiperspirants, lotions, or powders on the area to be tested. The test should be performed in a temperature-controlled room with the patient relaxed and comfortable.
2. Electrode placement: Electrodes are placed on the skin to measure sweat response. Typically, these electrodes are placed on the forearm, thigh, and foot.
3. Stimulation: Acetylcholine is applied to the skin via iontophoresis. This involves placing a small electrode containing the chemical on the skin and using a low electrical current to facilitate its absorption.
4. Sweat measurement: Sweat response is measured using a device that captures and quantifies the amount of sweat produced.
5. Interpretation: The results are interpreted by comparing the amount of sweat produced to normal values for the patient’s age and gender.

QSART is generally safe and well-tolerated, but some people may experience mild discomfort or a tingling sensation during the test. It is important to follow any instructions given by the healthcare provider before and after the test to ensure accurate results.

Quantitative Sudomotor Axon Reflex Test is contraindicated for certain individuals, such as those with pacemakers or other implanted medical devices.

Test Reliability

In one study, QSART test were performed on the left forearm and foot of 33 female and 29 male normal subjects aged 11 to 69 years. Acetylcholine, 10%, was electrophoresed for 5 mA-minutes in the forearm and 10 mA-minutes in the foot, and recording was continued for an additional 5 minutes. The mean sweat output in males was 2.7 and 3.0 times that in females in forearm and foot, respectively (p less than 0.0001). Studies in selected autonomic neuropathies confirm that quantitative sudomotor axon reflex tests will detect postganglionic sudomotor abnormalities sensitively and reproducibly.

References & More

• Low PA, Caskey PE, Tuck RR, Fealey RD, Dyck PJ. Quantitative sudomotor axon reflex test in normal and neuropathic subjects. Ann Neurol. 1983 Nov;14(5):573-80. doi: 10.1002/ana.410140513. PMID: 6316835.
• Riedel A, Braune S, Kerum G, Schulte-Mönting J, Lücking CH. Quantitative sudomotor axon reflex test (QSART): a new approach for testing distal sites. Muscle Nerve. 1999 Sep;22(9):1257-64. doi: 10.1002/(sici)1097-4598(199909)22:9<1257::aid-mus14>3.0.co;2-j. PMID: 10454723.