What does QSART stand for?

QSART stands for quantitative sudomotor axon reflex test. It measures the sweat response produced when acetylcholine stimulates the small autonomic nerves that supply sweat glands, giving an objective read on postganglionic sudomotor nerve function.

What is QSART used to diagnose?

It is used to help evaluate autonomic and small-fiber neuropathies, including conditions that damage the small nerves controlling sweating. It is typically combined with the clinical picture and other tests rather than used alone to name a specific disease.

Is the QSART test painful?

It is generally well tolerated. Acetylcholine is driven into the skin using a weak electrical current rather than a needle, and most people feel only mild tingling or warmth at the capsule sites. Specific expectations should be confirmed with the testing laboratory.

How is QSART different from a thermoregulatory sweat test?

A thermoregulatory sweat test uses a warm chamber to assess the entire sweat pathway from brain to gland and maps where sweating is present or absent across the body. QSART isolates the postganglionic nerve at specific sites. Pairing them can help localize where along the pathway a problem lies.

Why do sweat nerves matter for diagnosing neuropathy?

The small autonomic fibers that control sweating are among the first to be affected in several nerve disorders. Measuring their function with QSART can reveal small-fiber or autonomic nerve damage that other tests may miss, which is why it is used in autonomic laboratories.

Is this page medical advice?

No. It is an educational explanation of what QSART is and how it works, drawn from published sources. It does not interpret any individual result, and decisions about whether to have the test belong with a clinician.

Research

The QSART Test: Measuring Sweat and Nerve Function

The quantitative sudomotor axon reflex test (QSART) is a laboratory test that measures how well the small nerves controlling sweating are working. It uses a mild chemical, acetylcholine, driven into the skin by a weak electrical current to trigger a local sweat response, and a sensitive device records how much sweat is produced. Because those sweat nerves are part of the autonomic nervous system, QSART is used to help detect and characterize autonomic and small-fiber neuropathies. This page explains what QSART measures and how it works. It is educational and is not medical advice.

By the Sweat Explained Editorial Team · Published 2026-07-20 · Last reviewed 2026-07-20 · Educational information, not medical advice.

Key statistics at a glance

1983
year the QSART method was formally described by Low and colleagues at Mayo Clinic
Low 1983 (Ann Neurol)
Acetylcholine
the chemical driven into the skin to trigger the sudomotor axon reflex that QSART measures
Low 1983 (Ann Neurol)
Postganglionic
QSART assesses postganglionic sympathetic sudomotor fibers, the peripheral end of the sweat nerve pathway
Illigens & Gibbons 2009 (Clin Auton Res)
4 sites
standard recording locations (forearm and three leg or foot sites) used to map sudomotor function along the limb
Illigens & Gibbons 2009 (Clin Auton Res)
5 minutes
typical duration over which the evoked sweat response is recorded in the standard protocol
Low 2004 (Clin Neurophysiol)

What QSART measures

Sweating is controlled by small autonomic nerve fibers, and QSART is designed to test those fibers directly. It relies on a phenomenon called the axon reflex: when acetylcholine stimulates a sweat nerve ending, the signal travels back up the nerve, then down a branch to reach nearby sweat glands and make them secrete. Measuring that evoked sweat response gives an objective read on whether the postganglionic sudomotor nerves, the last stretch of nerve before the sweat gland, are intact and functioning.

This matters because those same small fibers are among the first to be damaged in several nerve disorders. Unlike a subjective report of feeling sweaty, QSART produces a quantitative measurement, which is why it is used in autonomic laboratories as part of a structured assessment of nerve function. The test was formally described by Low and colleagues at Mayo Clinic in 1983 (Low 1983).

How the test is done

During QSART, small capsules are placed on the skin, usually at the forearm and at several points down the leg to the foot. Each capsule has an outer compartment containing acetylcholine and an inner compartment where sweat is collected. A weak electrical current, a process called iontophoresis, drives the acetylcholine into the skin without a needle (Illigens & Gibbons 2009). This stimulates the axon reflex, and a device called a sudorometer measures the volume of sweat released over time, typically for several minutes.

Recording at multiple sites lets the laboratory map how sudomotor function changes along a limb, which helps distinguish a length-dependent pattern (worse farther from the trunk) from other patterns. The test is generally well tolerated; sensations are usually limited to mild tingling or warmth at the capsule. QSART is often performed alongside other autonomic tests, such as heart-rate and blood-pressure responses, as part of an autonomic reflex screen.

What the results can indicate

QSART results are interpreted by comparing sweat output to normal values for the site, age, and sex. Broad patterns described in the literature include:

Reduced or absent sweating. A low or absent response points to damage of the postganglionic sudomotor fibers, as can occur in autonomic and small-fiber neuropathies.
Small-fiber neuropathy. QSART is one of the tools used to support a diagnosis of small-fiber neuropathy, often together with skin biopsy and sensory testing.
Autonomic neuropathies. It is used in the assessment of conditions such as diabetic autonomic neuropathy and other causes of autonomic failure.
Persistent or excessive responses. Prolonged or exaggerated sweat responses have been described in some pain and autonomic conditions.
Mapping the pattern. Comparing sites helps show whether nerve involvement is length-dependent, which informs how a neuropathy is characterized.

How QSART compares with other sweat tests

QSART is one of several ways to study sweating. Each answers a different question (Illigens & Gibbons 2009; Low 2004).

QSART compared with other sweat and sudomotor tests
Test	What it assesses	Notes
QSART	Postganglionic sudomotor nerve function via the axon reflex	Quantitative; done at multiple sites in an autonomic laboratory
Thermoregulatory sweat test (TST)	The whole sweat pathway, from brain to gland, over the body surface	Uses a heated chamber and an indicator powder to map where sweating is present or absent
Minor's starch-iodine test	Where sweating occurs on the skin (a visual map)	Simple and qualitative; often used to outline areas of heavy sweating
Gravimetry	How much sweat is produced, by weight	Measures sweat quantity rather than nerve function
Silastic sweat imprint	Sweat droplets from individual glands	Can estimate active gland density and droplet size

These tests are complementary. TST maps the whole pathway, while QSART isolates the postganglionic nerve, so pairing them can help localize where a problem lies.

Availability and limitations

QSART is a specialized test performed mainly in autonomic laboratories, so it is not available everywhere. Results are influenced by factors such as age, sex, body site, skin temperature, hydration, and certain medications, which is why laboratories use their own normal values and ask about medications beforehand. Because sweat responses vary, the test is interpreted in context rather than as a single pass-or-fail number.

It is also just one piece of an autonomic evaluation. A neurologist typically combines QSART with the clinical picture, other autonomic measurements, and sometimes skin biopsy or blood tests. On its own, an abnormal QSART does not name a specific disease; it indicates that the small sudomotor nerves are affected and helps guide the wider workup.

What this means in plain terms

QSART turns something invisible, the health of the tiny nerves that switch sweat glands on, into a measurable signal. By stimulating the skin with acetylcholine and recording the sweat that follows, it tells clinicians whether those nerves are responding normally, weakly, or not at all. That information is most useful in evaluating suspected autonomic or small-fiber nerve problems.

For a general reader, the key point is that sweating can be used as a window onto nerve function, and QSART is one of the main tools for looking through it. This page explains what the test is and does; it is educational and is not medical advice, and decisions about testing belong with a clinician.

Methodology and limitations

This page draws on the primary description of QSART (Low et al., Ann Neurol 1983), a review of sweat testing for autonomic function (Illigens & Gibbons, Clin Auton Res 2009), a review of sudomotor evaluation (Low, Clin Neurophysiol 2004), and studies describing QSART's role in small-fiber neuropathy (Thaisetthawatkul et al., Muscle Nerve 2013) and its measurement characteristics (Sletten et al., Muscle Nerve 2010). The test method, recording sites, and stimulus were traced to those sources.

Limitations: QSART protocols and normal values vary between laboratories, and sweat responses are affected by age, sex, site, temperature, and medications, so results are interpreted against local reference data rather than a universal threshold. QSART assesses postganglionic sudomotor fibers specifically and does not, by itself, diagnose a particular disease; it is one component of a broader autonomic evaluation. This page is educational and is not medical advice; testing decisions rest with a clinician.

Frequently asked questions

What does QSART stand for?: QSART stands for quantitative sudomotor axon reflex test. It measures the sweat response produced when acetylcholine stimulates the small autonomic nerves that supply sweat glands, giving an objective read on postganglionic sudomotor nerve function.
What is QSART used to diagnose?: It is used to help evaluate autonomic and small-fiber neuropathies, including conditions that damage the small nerves controlling sweating. It is typically combined with the clinical picture and other tests rather than used alone to name a specific disease.
Is the QSART test painful?: It is generally well tolerated. Acetylcholine is driven into the skin using a weak electrical current rather than a needle, and most people feel only mild tingling or warmth at the capsule sites. Specific expectations should be confirmed with the testing laboratory.
How is QSART different from a thermoregulatory sweat test?: A thermoregulatory sweat test uses a warm chamber to assess the entire sweat pathway from brain to gland and maps where sweating is present or absent across the body. QSART isolates the postganglionic nerve at specific sites. Pairing them can help localize where along the pathway a problem lies.
Why do sweat nerves matter for diagnosing neuropathy?: The small autonomic fibers that control sweating are among the first to be affected in several nerve disorders. Measuring their function with QSART can reveal small-fiber or autonomic nerve damage that other tests may miss, which is why it is used in autonomic laboratories.
Is this page medical advice?: No. It is an educational explanation of what QSART is and how it works, drawn from published sources. It does not interpret any individual result, and decisions about whether to have the test belong with a clinician.

Sources

Primary peer-reviewed studies and official sources first, then reviews and institutional framing (secondary).

Low PA, Caskey PE, Tuck RR, Fealey RD, Dyck PJ. Quantitative sudomotor axon reflex test in normal and neuropathic subjects. Ann Neurol. 1983;14(5):573-580. Original description of the QSART method. Journal
Illigens BM, Gibbons CH. Sweat testing to evaluate autonomic function. Clin Auton Res. 2009;19(2):79-87. Review of QSART and other sudomotor tests. Full text
Low PA. Evaluation of sudomotor function. Clin Neurophysiol. 2004;115(7):1506-1513. Overview of methods to assess sweating and sudomotor nerves. (secondary) Journal
Thaisetthawatkul P, Fernandes Filho JA, Herrmann DN. Contribution of QSART to the diagnosis of small fiber neuropathy. Muscle Nerve. 2013;48(6):883-888. QSART in the evaluation of small-fiber neuropathy. (secondary) Journal
Sletten DM, Weigand SD, Low PA. Relationship of Q-sweat to quantitative sudomotor axon reflex test (QSART) volumes. Muscle Nerve. 2010;41(2):240-246. Measurement characteristics of sudomotor testing. (secondary) Journal

How to cite this page

Sweat Explained. The QSART Test: Measuring Sweat and Nerve Function. Published 2026-07-20; last reviewed 2026-07-20. Available at: https://sweatexplained.com/research/quantitative-sudomotor-axon-reflex-test-qsart

Please cite the original studies for the underlying figures. Journalists are welcome to link to this page; the charts are original renderings of the cited data.