NHS Foundation Trust
Sweat Test
Your doctor will always explain the need to do a sweat test
before the test is carried out
Every
Matters
1
The Sweat Test
A sweat test is a screening test requested by your doctor when the
diagnosis of Cystic Fibrosis (CF) is being considered. People with CF
have an increased amount of sodium and chloride (salt) in their sweat.
The test is done frequently in the hospital.
The test itself is simple, painless, reliable, and it can be carried out on
children of all ages.
Cystic Fibrosis
Cystic Fibrosis is a disease that is inherited through families and is
not passed on through infections. It affects approximately one in 2500
people.
This means that it would be diagnosed in approximately one or two
children in the Leighton Hospital area each year.
Cystic Fibrosis is a difficult disease to diagnose and it has similar
symptoms to several other minor ailments. Because of this the
majority of children who have a sweat test will turn out not to have
CF.
CF affects the digestive system and the lungs and the test is done when
children show some of the following symptoms (Please note that these
symptoms do not mean that a child has CF):
• Poor weight gain or slower than normally expected growth
• Recurring bouts of diarrhoea or oily motions that are difficult to
flush away
• Difficulty in digesting food
• Frequent coughs, colds, chest infections
• A family history of the disease
It is important to diagnose CF as soon as possible so that the best
treatment can be started. A positive result may mean that your child
has cystic fibrosis (CF) but a final diagnosis will take into account
other symptoms, clinical findings and test results.
Preparation for the test
• There are no restrictions on eating or drinking before the test
• Please do not use soap or lotions on your child’s forearms on the
morning of the test
• All other medicines can be taken as usual
• You could bring a cardigan or blanket for your child to wear during the
test
How the test is done
The sweat test is a simple test that takes approximately one hour.
A trained member of staff from the Out-Patients Department will do this test,
usually in the Children’s Outpatients Department.
The first part of the test is to stimulate sweat production. This is done using
a tiny painless electric current passing between two electric pads that are
loosely strapped to the child’s forearm. Each pad contains a drug called
Pilocarpine, which stimulates sweating when it touches the skin.
Does the test hurt?
The child may feel a tickling or tingling sensation or a feeling of warmth – but
it does not hurt and there is virtually no risk of a “shock”.
No needles are involved. This test will leave some redness and sweat on the
area where the test is done and this is normal.
The sweat is collected in a tiny coil. You will be asked to wait for about 30
minutes for the sweat to be absorbed. During this waiting time the area will
be checked regularly but the child can play normally.
The coil is then removed and sent to the laboratory. The result of the
test will indicate the amount of salt that the sweat contains.
Sometimes infants or young children do not make enough sweat for the
laboratory test or for the result to be reliable. If that happens the test may
need to be repeated. Clinic staff will contact you to arrange a suitable time if
the test needs to be repeated.
Results of the Sweat Test
The results of the test will be discussed with you at a clinic appointment.
The majority of tests (90%) will come back as normal, which makes it very
unlikely that the child has cystic fibrosis. However, around 10% of the tests
will show a raised salt level, most showing intermediate levels of salt – not
high enough to make a diagnosis of cystic fibrosis, but not low enough to
be absolutely sure the child has not got cystic fibrosis. For these children
we will need to repeat the sweat test, using a different method, at the
Royal Liverpool Children’s Hospital. This will be organised for you. Again
the majority of these tests turn out to be normal.
Further Questions
If you have further questions, please speak to the doctor who referred your
child for this test.
References
Retrospective audit of the
Macroduct sweat collecting system
and conductivity analysis after its
introduction to a district general
hospital.
R Jayaraj, D Lacy, D Neithercut
25th European CF Conference 2002
Children’s Hospital Medical Centre
of Cincinnati (1998) “Sweat
Chloride Test”. Patient Education
Programme ON LINE 30.11.01
Cystic Fibrosis Foundation (2001)
“Sweat Testing Procedure and
Commonly Asked Questions.
“Publications ON LINE 30.11.01
Gale Encyclopaedia of Childhood
and Adolescence (1998) “Sweat
Test”. Gale Research ON LINE
30.11.01
Krishnan Chandran Children’s Centre
Leighton Hospital
Middlewich Road,
Crewe, Cheshire,
CW1 4QJ
Direct Line: 01270 612288
www.mcht.nhs.uk
Printed on certified PEFC paper. Sourced from sustainable forests.
IMPRESSIONS DESIGN & PRINT 01270 767661
Printed April 2013 Review April 2015 • Ref:WCSH/KCCC/0010413