health

It is possible to diagnose CF before birth around the eleventh week of
pregnancy by testing a small piece of tissue from the placenta, the temporary
organ that allows for exchange of nutrients and waste products
between the mother and baby. After the sixteenth week of pregnancy, the
fetus can be tested by amniocentesis, a procedure that involves withdrawing
a small amount of fluid from the sac that surrounds the baby
before birth.
Many hospitals have newborn screening programs to evaluate
babies for CF. Although the screening methods are not diagnostic tests
in the strict sense, they can be used to rule out CF in most babies. In
addition, by identifying babies who should be tested further for CF,
screening allows treatment for the disease to be started as early as
possible.
The sweat test has been considered the best diagnostic test for cystic
fibrosis for over forty years. It measures the amount of chloride in the
person’s sweat. To perform the test, the doctor applies a chemical that
causes sweating on a small area of the person’s arm or leg. An electrode
is attached to the treated area and a mild electrical current is used to stimulate
sweating. The patient may feel a tingling or warm sensation. After
about five minutes, the sweat from the treated area is collected on a piece
of filter paper and sent to a laboratory for analysis. One benefit of the
sweat test is that the values are not changed as a person grows older or
affected by temporary illness.
Another more recent test that can be used to diagnose CF is genetic
testing of a sample of the patient’s blood for mutations in the CFTR
gene.