Introduction
This fact sheet has been produced to provide information for people who need a sweat test. In addition, the leaflet explains how you can get the results of your tests and what they mean.
For further details please see www.labtestsonline.org.uk which is written by practising laboratory doctors and scientists to help you understand the many clinical laboratory tests that are used in diagnosis and treatment.
What is a sweat test?
A sweat test involves the collection of sweat and the measurement of the amount of salt that is in it.
Why does this need to be carried out?
The test is carried out on children or adults where cystic fibrosis (CF) is a possible diagnosis because they are having frequent chest infections, frequent and unexplained pale stools, problems gaining weight or growing properly or as part of a screening programme. People with CF have a high amount of salt in their sweat.
There are also other rarer indications for a sweat test. A positive result may mean that you or your child has CF, but a final diagnosis will take into account other symptoms, clinical findings and test results.
A normal result can be helpful in ruling out CF. It is important to diagnose this condition as soon as possible in order to begin appropriate treatment.
Who does this test?
A Biomedical Scientist from the Chemical Pathology Department will perform the test. We would like parents or legal guardians to be present if patients are under 16 years of age.
Does the test hurt?
Some people experience a tingling sensation on the arm or leg where the sweat has been collected. No needles are involved.
How is the test carried out?
Special gels, soaked in a chemical called pilocarpine that stimulates sweat production, are placed on the lower arm or leg. These are tied in place and a small electric current is passed through the gel from a battery box to further stimulate the sweating process.
The test is not painful, although you may experience a tingling sensation. The gels are left in place for about 5 minutes and then removed. There may be a red mark where the pilocarpine has stimulated the skin. This is usual and should fade within a few hours.
The skin is then carefully washed with pure water and dried. A small plastic coil is placed over the stimulated area and tied. You will then be asked to wait for about 30 minutes for the sweat to be absorbed into the coil device. Please do not let your child tamper with the collection coil once in place.
Your child can play as usual during the 30-minute period. The coil is then removed and taken to the laboratory for analysis.
The Results
Most tests are normal, as CF is an uncommon disease, and most cases are picked up shortly after birth.
In most cases the results will clearly show either a high (abnormal) or normal salt level in the sweat but sometimes the results can be borderline and the test will need to be repeated. In a few cases the test may need to be repeated for technical reasons such as not enough sweat has been collected. Many doctors like to confirm an abnormal sweat test with a second sweat test.
How long will it take to get results?
The sweat is usually analysed on the day of collection and results will then be promptly sent to the relevant Consultant / Doctor.
Who will inform me of the results?
Most tests are normal, and the result is sent to you and your GP by letter. If the test is borderline or abnormal, your child will be recalled within a few days for a repeat test and further discussions.
Further questions
If you have questions about the process of doing the sweat test, please contact the Paediatric Department or your Biochemistry Department at your local Hospital.
If you have further questions about the need for a sweat test for yourself or your child, please speak to the doctor who has referred you for this test as they can give you further information.
Benefits
The benefit of doing the test is that it will provide your doctor with important results which will help with diagnosis and / or treatment.
Risks
Some people experience a tingling sensation on the arm or leg where the sweat has been collected and a small red patch might appear on the skin. This will fade very quickly. While the system used at the hospital is superior to previous methods, burns during sweat stimulation have not been totally eliminated. The manufacturers have estimated a frequency of 1 burn in 50,000 procedures.
Alternatives
There are no alternative tests that could be used to the one that you have been asked to undertake.
Contact details for further information
If you have any queries please ring your local laboratory:
Goole Tel. 03033 304025 Reception 0830-1600 (Mon-Fri)
Grimsby Tel. 03033 302677 Reception 0800-1700 (Mon-Fri)
Scunthorpe Tel. 03033 302641 Reception 0800-1700 (Mon-Fri)
Louth Tel. 01507 600100 Ext 1253 Reception 0830-1630 (Mon-Fri)
Any comments, compliments, concerns or complaints
If you have any other concerns please talk to your nurse, therapist or doctor. Our Patient Advice and Liaison Service (PALS) is available on 03033 306518 (Grimsby, Scunthorpe and Goole). You can also contact [email protected]
As a Trust we value equality of access to our information and services, therefore alternative formats are available on request at [email protected]
Review Information
Date of issue: May 2024
Review Period: May 2027