Sweat Chloride Test (cont.)

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How long does the test take?

The sweat chloride test usually takes about one-half to one hour.

What is done with the sweat?

The sweat is collected on a specialized filter paper. After determining that enough sweat has been collected to ensure test reliability, the amount of chloride in the sweat is measured. This is considered a specialized test, and not all institutions have experience with the techniques, and poor collection techniques can result in false negative results.

What are normal sweat chloride levels?

The normal sweat chloride values are 10-35 milliequivalents per liter.

What is the sweat chloride level in cystic fibrosis?

Patients with cystic fibrosis usually have a sweat chloride value greater than 60 milliequivalents per liter.

What if the sweat chloride is intermediate (between normal and the usual cystic fibrosis levels)?

Intermediate values between 35 and 60 milliequivalents per liter may be seen in some cystic fibrosis patients (and in some normal children). In those cases, the sweat chloride test should be repeated in the very near future.

Can a cystic fibrosis child have a normal sweat chloride level?

In a severely malnourished patient with cystic fibrosis, the sweat chloride level may be normal. However, once the malnutrition is corrected, the test becomes positive.

Can the sweat chloride be high without having cystic fibrosis?

There are a few rare conditions which produce a false positive sweat chloride test. Such situations include diseases of the adrenal, thyroid, or pituitary glands; rare lipid storage diseases; and infection of the pancreas. Generally, however, these children are easily differentiated from patients with cystic fibrosis by their clinical condition, and molecular tests for cystic fibrosis can be done to clarify the diagnosis.

Medically reviewed by a Board Certified Family Practice Physician

Medically Reviewed by a Doctor on 6/30/2015

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