Quantitative Sudomotor Axon Reflex Test (QSART)

What is a QSART?

A QSART test (quantitative sudomotor axon reflex test or sweat test) looks at the nerves that control your sweating. The test involves an electrical stimulation on your skin called iontophoresis. QSART measures the volume of sweat produced by this stimulation.

What is a QSART test for?

A QSART can help diagnose autonomic nervous system conditions, peripheral neuropathies and some types of pain disorders. Your autonomic nervous system controls how your body’s internal organs work, which includes regulating your body temperature, blood pressure, heart rate and digestion.

Your provider might use this test, among others, to diagnose the following conditions:

• Autonomic neuropathy.
• Complex regional pain syndrome (CRPS).
• Diabetes-related neuropathy.
• Multiple sclerosis.
• Postural orthostatic tachycardia syndrome (POTS).
• Sjögren’s syndrome.
• Small fiber neuropathy.

How do I prepare for a QSART?

Your healthcare provider will meet with you before a QSART to let you know what to expect. They’ll also give you specific instructions to follow so you can prepare. These may include:

• Stop taking certain medications that may change the results of the test.
• Avoid tobacco products for up to four hours before the test starts.
• Don’t wear compression garments or stockings on the day of the test.
• Make changes to when you eat and drink before the test.
• Wear loose, comfortable clothing on the day of the test.
• Don’t use any lotions or body creams on the day of the test.

If you have any questions about how to prepare for a QSART, ask your provider before your test.

Can I eat or drink before a QSART?

You’ll need to make some slight changes to what you eat and drink before a QSART. Your provider may recommend the following:

• Don’t eat or drink anything that contains caffeine eight hours before the test.
• Don’t drink any beverages containing alcohol 12 hours before.
• Eat a light meal at least three hours before.
• Drink plenty of water and stay hydrated the day before.
• Don’t drink any beverages three hours before.

What medications can I take before a QSART?

You should continue taking all of your medications unless your provider instructs you to stop taking them.

Some medications can interfere with the QSART results, including:

• Analgesics.
• Antidepressants.
• Antihistamines.
• Anti-inflammatory agents.
• Aspirin.
• Blood pressure medications.
• Diuretics.
• Over-the-counter cold or cough medications (decongestants).

You may need to stop taking these medications up to 48 hours before the test.

How is a QSART done?

You can expect the following during a QSART:

1. You’ll remove your shoes and socks.
2. You’ll sit or lie flat on your back on an exam table, if possible.
3. Your provider will clean and dry your skin where they’ll perform the test, usually on your foot, leg and wrist.
4. Your provider will place four electrodes (small plastic patches) on your skin. Typically, three are on your leg and one on your wrist. They’ll also rub acetylcholine on your skin. Acetylcholine is a naturally occurring neurotransmitter in your body. This solution on your skin stimulates your sweat glands during the test.
5. The QSART machine is turned on and passes a small electrical current through the electrodes on your skin.
6. Your body will produce sweat, which the machine will then measure.
7. Your provider may move the electrodes to different parts of your body and repeat the above steps.

How long does a QSART take?

A QSART takes approximately 45 minutes to one hour.

Is a QSART painful?

A QSART isn’t painful, but you may feel some discomfort. The movement of electric currents might feel like a tickling, prickling or mild burning sensation where the electrodes sit on your skin.

If you feel any pain, let your provider know.

What can I expect after a QSART?

After the test, your provider will remove the electrodes from your skin and you can put your socks and shoes back on. You might notice some skin irritation or discoloration, like redness or a darker skin tone, in the areas where your provider placed electrodes. This usually goes away in a few hours.

The data from the test are then sent to your referring physician. They’ll contact you when the results are ready. This usually takes a few days.

What are the risks of a QSART?

A QSART isn’t invasive or dangerous. You may feel uncomfortable sensations during the test. But most people can get through it without any issues. If you’re unable to tolerate the prickling sensation of the electrical current moving under your skin, your provider may offer alternative forms of testing.

How do I interpret QSART test results?

Your provider will analyze the data collected from a QSART and have the results back to you in a few days. Test results look at the following:

• How long it takes for your body to start sweating (onset latency).
• When you reach the highest amount of sweat produced (peak sweat production).
• How much sweat you produce during the entire test (sweat volume).

These results could be normal or abnormal.

QSART normal values

A normal QSART value (or negative result) identifies that the amount of sweat you produce and the time when you start sweating is as expected for your age and sex.

For example, it could take one to two minutes for your body to start producing sweat. The amount of sweat your body produces increases for up to five minutes, and then decreases.

Normal values vary based on the type of QSART equipment used during the test. Your provider will let you know what a normal result looks like.

What does a positive QSART mean?

A positive QSART result means that the test results are abnormal. This indicates that something is interfering with how your autonomic nervous system functions.

For example, your provider may notice a delay in how long it takes your body to produce sweat or an increased amount of sweat produced during the test.

A positive QSART result isn’t a diagnosis, but it tells your provider that there might be an underlying issue. Your provider may run additional tests or offer treatment options to help you feel better.