Facts About Cystic Fibrosis

Part 2

How is Cystic Fibrosis Diagnosed?

In some cases cystic fibrosis can be diagnosed as early as at birth. In such cases the diagnosis is aided by the initial presentation of meconium, which is the black colored, tar-like contents of the bowels, which in cases of cystic fibrosis creates a blockage in the bowel of the newborn and in some cases surgery may be necessary to correct the problem. If diagnosis is not sought by this obvious presenting problem, some children and even adults can live for years without symptoms being severe enough to even question cystic fibrosis is present even though it is inherited at birth. There are however situations where symptoms may begin to appear and begin to increase in frequency and severity, however diagnosis can be clouded by the fact that symptoms are similar to those found in other less serious conditions.

Cystic fibrosis may be questioned by increased prevalence of chest infections which in some cases require hospitalization and intravenous antibiotics, that twinned with reports of excessive ‘salty’ sweating and the appearance of ‘oily’ stools may indicate that cystic fibrosis is present and formal testing is then required. The ‘gold standard’ test for cystic fibrosis is a test known as the ‘sweat test’ and this crudely measures the amount of sodium concentrated in a sample of the patients sweat. Sweat on the skins surface usually contains very little sodium chloride however the sweat in the case of a person with cystic fibrosis contains 2 to 5 times more sodium chloride than the average person who does not have the condition.

A substance called ‘Pilocarpine’ is placed on the arm of the patient and this encourages the body to produce excess amounts of sweat. Electrodes are placed over gauze and a mild electrical current is then used to generate the sweating process. The sweat is subsequently collected on a piece of gauze and the volume of salt crystals is then measured using a laboratory technique. When the sweat test is performed on babies and small children it may need to be repeated as these patients tend to sweat less and satisfactory results may not be gained from one test alone (WebMD, Updated 2007).

Results of the sweat test will either be high, normal or in some cases borderline. If the sodium levels are high this is a reasonable indicator of cystic fibrosis however the test is often repeated to be sure. In cases where results are ‘borderline’ the test too will be repeated. Where sodium levels are within normal limits it can be concluded that cystic fibrosis is not present. In cases where an infant may have had a normal sweat test near the time of birth, but goes on to indicate symptoms of cystic fibrosis, a sweat test will be repeated later on and in some cases positive results are shown. In the event of this it is likely that the sodium sample collected in the earlier test was not sufficient to make a diagnosis.