SUDOSCAN
Frequently Asked Questions
Q. Why test sudomotor function?
A. "Sweat response may be the most sensitive test in detecting distal
small fiber neuropathy." (see publications by Low et al. and Gibbons et al). Eccrine glands that are responsible
for sweat response receive a rich supply of blood vessels and are innervated by sympathetic C nerve fibers
(autonomic nervous system). These fibers are thin and long and so can be impaired at the early stage of different
metabolic diseases. Testing sudomotor function can be a fast and accurate method for detecting early stages of
neuropathies.
Q. What is SUDOSCAN?
A. SUDOSCAN is a medical device that has been cleared by the FDA as a
galvanic skin response test. Galvanic Skin Response (GSR) is a change in the electrical properties of the skin in
response to different kinds of stimuli. In GSR, changes in the voltage measured from the surface of the skin are
recorded. The main origin of the signal has suggested to be the activation of sweat glands (sudomotor function).
Q. What does SUDOSCAN measure?
A. SUDOSCAN evaluates sudomotor function on the palm of the hands and
sole of the feet where the density of sweat glands is maximal.
The underlying technology is based on established principles on the electrochemical reaction between chloride
(found in sweat) and nickel (which is a component of the electrodes used in SUDOSCAN). A low DC voltage (<4 volts
is applied, generating a current relative to chloride (ion) flow supplied by the sweat glands and ducts. An Electro
Skin Conductance (ESC) is calculated for the hands and feet on this basis of the current generated and the voltage
supplied.
Similar to cardiologic stress test. for which the exercise is used as a stimulus to capture specific information
that is not assessable in resting state, SUDOSCAN too relies on an electrical stimulus of sweat chloride to capture
information about the sweat dysfunction that cannot be diagnosed in usual conditions.
Because the skin’s stratum corneum acts like an electrical capacitor allowing only the conduction of chloride to
pass to the surface hands and feet electrodes via the sweat duct when a low voltage stimulation is applied, we can
be certain that we’re targeting the underlying sweat gland and its sympathetic innervations.
This underlying theory has been confirmed in a comparative study performed on patients with Cystic Fibrosis (who
have high sweat chloride concentration) and controls (see publication by Hubert et al).
Q. Who should get tested on SUDOSCAN?
A. Anyone can get tested on SUDOSCAN to assess their sudomotor
function unless they have a specific contra-indication that would prevent them from performing a scan. As
previously described, the potential uses for SUDOSCAN include evaluation of peripheral neuropathy and follow-up for
diabetic patients.
Q. What are the reasons to get yourself tested on SUDOSCAN?
A. Small C fiber nerve damage can be observed in subjects with
prediabetes or metabolic syndrome. Because SUDOSCAN is non-invasive and takes only 2 minutes to run, you can
benefit from knowing your hands and feet conductances – in first establishing your baseline levels, then repeating
the test periodically to monitor your numbers. SUDOSCAN allows you to have: Immediate knowledge of sweat gland
functioning as indicator of peripheral nerve functioning. Biofeedback: a way to quantify the “status” of your
peripheral nerves upon lifestyle changes ex. Exercise and its benefits.
Q. What information does SUDOSCAN provide? How can the
physician use this information to help his/her patient?
A. SUDOSCAN test results are provided in hands and feet conductances.
High conductances correlates with normal sweat function and healthy nerve innervation (small C-fibers). Low
conductances represent peripheral or autonomic neuropathy.
Physicians can use SUDOSCAN in various medical settings:
Proactive monitoring: Medicine is trending towards prevention of the onset of a disease or complication. Since the
long, unmyelinated, sympathetic c-fibers slowly degenerate yet quickly regenerate with changes (good or bad) in a
patients environment; physicians can use this information to determine whether or not a patient is “at risk” of
developing a complication and take proactive measures with treatment options.
Assessing the level of intensive glycemic control for diabetics. It is important to determine whether or not a
patient has a neuropathy before prescribing intensive forms of glycemic treatment.
Patient drug or lifestyle compliance: SUDOSCAN allows for a physician to quickly determine Sudomotor functioning
as a biomarker for peripheral nerve integrity. Patient compliance can quickly be determined based on how good or
how bad their results are. This information is complimentary to traditional blood based testing, but is extremely
fast and offers immediate results. Quantitative results introduce no subjectivity via patient verbal responses.
Q. Does gender play a factor in the results?
A. Evaluation of sudomotor function using other tests such as QSART
has shown generally lower measures (in sweat output) in women compared with those on men. This can be explained
by lower sweat rates in women. Measurements performed by SUDOSCAN don’t depend on sweat rate. A study performed
on more than 500 women and more than 200 men show no significant differences in hands’ and feet’ ESC. This will
be confirmed in future pending studies on larger group populations.
Q. Does ethnicity play a role?
A. Sweat rate can vary with ethnicity. As previously mentioned,
SUDOSCAN measurements do not depend on sweat rates. Studies that have been performed in India, China, Germany,
France and other European countries show no notable differences in hands and feet ESC in Asian subjects as
compared with European subjects. However larger studies are necessary to confirm this hypothesis.
Q. Can my age influence the SUDOSCAN reading?
A. SUDOSCAN measured conductance levels do not depend on age.
Q. Does room temperature affect the test results?
A. Clinical tests run at different temperatures (changes of more
than 5°C) demonstrate that temperature variance do not have impact on test results. Hands and feet that are
poorly involved in thermoregulation due to their small area and thus are less temperature dependent than other
parts of the body for their sweat rate. Theoretically, extreme cold temperature on the electrodes could result
in vasoconstriction, whose effect has not been yet studied. Therefore, avoid performing test measurements if
the electrodes are too cold.
Q. Does exercising just before being evaluated impact test
results?
A. Given sweat rate changes with exercise it was important to
evaluate the effects of exercise on SUDOSCAN tests. Measurements were performed before and after high level
exercise on more than 100 subjects. Tests show a coefficient of variation of 13% for the hands and of 4% for
the feet between these two measurements. These results confirm that SUDOSCAN measurements are not dependent on
sweat rate.
Q. Can I use Sudoscan for type 1 diabetes?
A. Contrarily to type 2 diabetes, diagnosis of type 1 can occur
before the onset of complications including small C-fiber neuropathies. Thus at the early stages of the disease
if the patient treatment is well-balanced sweat function should be normal and conductances values as measured
by SUDOSCAN should not be decreased. However with the progress of the disease, especially if the patient
treatment is not fully adapted, small C-fibers damages will occur and sweat dysfunction should be evidenced
through a decrease in conductances as measured by SUDOSCAN. Due to the absence of pre-diabetes stage small
C-fiber damages can be lower and occur at later stages as compared to type 2 diabetes.
Q. Can children be tested?
A. There is no safety concern testing children on SUDOSCAN. However,
due to hormonal changes in children, it is difficult to produce consistent and accurate ESC readings. We
recommend children under the age of 18 not to be scanned due to fluctuations in conductance levels.
Q. How does SUDOSCAN correlate with HbA1c?
A. HbA1C is used to monitor glycemic levels for the past 3 month
period. SUDOSCAN is not a blood-based test but focuses on the assessment of the small C nerve fibers. As such,
SUDOSCAN is a test that can be performed in complement to HbA1c. There is no strict correlation evidenced
between HbA1C and Sudocan results. In research studies performed, we’ve observed cases where there were
significant differences in SUDOSCAN results yet no differences measured by HbA1c testing.
Q. How does SUDOSCAN correlate with EMG testing?
A. SUDOSCAN is used for small fiber neuropathy evaluation. EMG
is used to test large fibers.
Q. Is SUDOSCAN reimbursed? And how much?
A. Yes. Medicare and Medicaid are consistent with their good
reimbursement for this test. The level of reimbursement varies depending on geography and payer. In many
states such as New York where SUDOSCAN is currently used, physicians have been very satisfied with the level
of reimbursement.
Q. How often can you or should you retest?
A. Retest based upon Sudocan results and physician
recommendations. If your conductances are within normal tolerances, retesting every 9 to 12 months is
typical. Patients with peripheral neuropathies can be tested every three months to follow-up treatment
protocols.
Q. Is SUDOSCAN part of the protocol regiment for
physicians today?
A. At the moment physician have no tools to quickly and easily
screen peripheral neuropathy, other the use of biopsy methods that are clearly invasive in nature. Skin
biopsies are not performed routinely, especially on diabetic patients with feet lesions. This leaves
SUDOSCAN, which has huge potential to be used by physicians to follow-up patients with Type 2 diabetes as
part of the ADA guidelines.
Q. Who is using SUDOSCAN today?
A. SUDOSCAN is used in clinical settings by general
practitioners and specialists throughout the US. SUDOSCAN is also proving to be an invaluable research tool
for hospitals and major study centers in clinical studies. It is currently deployed in a dozen institutions
and being received with enormous praise by key opinion leaders in the fields of neuropathy, nephropathy,
endocrinology and cardiology.
Q. Can I get tested if I have a pace-maker?
A. Since only direct current is applied during a SUDOSCAN test,
it does not interfere with pace-maker electronics; therefore SUDOSCAN should be safe to use in a subject
with a pace-maker.
To confirm that there is no safety concern tests have be performed to check Electromagnetic Compatibility
according to ANSI/AAMI PC69:2007: Active implantable medical devices — Electromagnetic compatibility —
EMC test protocols for implantable cardiac pacemakers and implantable cardioverter guidelines. Conclusion
of the tests performed by Laboratoire Centrale des Industries Electriques (LCIE, Fontenay aux Roses,
France) is that “SUDOSCAN is compliant according to ANSI/AAMI PC69: 2007 (Annexe M) standard”. (Report
October, 2012).
However we recommend that patients with pace-makers perform Sudocan testing in the presence of a medical
doctor.
Q. What if I’m on Beta blockers?
A. Beta-blocker that are now cardioselective should not
interfere with SUDOSCAN measurements. However additional testing is needed to confirm this and the potential
effect of other cardiovascular drug.
Q. What if I’m on anti-diabetic drugs?
A. At the moment an observational study performed in an
outpatient consult clinic in Germany on two groups of patients with type 2 diabetes, the first one receiving
insulin, the second one other anti-diabetic drugs evidenced that after one-year follow-up patients receiving
insulin had an improvement in their conductances while the others had a small decrease. These preliminary
results have to be confirmed in a clinical study performed on a larger population.