As with most conditions CF is diagnosed using laboratory tests, medical history (symptoms) and physical examination.
For a small percentage of infants, the first symptom of CF is a blocked intestine at birth called meconium ileus.
Meconium is the black sticky secretion from a baby’s bowel which is normally passed in the first 24 hours post-birth. In some babies with CF the meconium is too thick to pass and blocks the intestine, needing enemas or surgery to remove it.
In New Zealand all newborn infants are screened for CF using the Guthrie Heel Prick test. This test, usually carried out 48 hours after birth, samples blood from the baby’s heel and screens it for rare metabolic disorders.
One of these tests measures the amount of pancreatic enzymes in the baby’s blood. This measurement of pancreatic enzyme levels is not a definitive diagnosis, but indicates the babies who may have Cystic Fibrosis. If the level of enzymes is abnormal, another sample from the same blood card will be used to test for the four or five most common mutations causing CF in New Zealand.
In a very small portion of the population the screening is inconclusive.
If your child has been identified as a person who may have CF by the Heel Prick Test, or later development of symptoms, a ‘sweat’ test will be performed to determine the likelihood that they have the condition.
The sweat test involves stimulating a small area of skin on the arm to produce sweat, which is analysed for salt concentration. In Cystic Fibrosis there is an excessive concentration of salt in the sweat. The sweat test will usually be performed at least twice.
Genetic testing will identify the type of gene variation that a patient has. There is some relationship between the genetic variation and CF severity, but it is not simple to predict. CF severity varies even in people with the same gene variation. This may be caused by other genetic and environmental factors.
Knowing your CF genes is like knowing your blood type. It’s interesting, but will not tell you how healthy a child will be, how well they will do in life or how long they will live.
If a family history of CF is known or suspected, family members can be tested to find out if they are carriers of the faulty CF gene. A simple blood sample or scraping from the inside of the cheek can be tested. This can be arranged through your GP.
Regional Genetic Health Services in New Zealand can discuss with those couples at risk of having children with CF, the genetic risk and the reproductive options available. These options could include prenatal testing and pre-implantation genetic diagnosis (PGD).
Genetic Health Service contact numbers:
Genetic Health Service – Northern Hub
Toll Free: 0800 476 123
Genetic Health Service – Central Hub
Toll free: 0508 364 436
Genetic Health Service – South Island Hub
Toll free: 0508 364 436