Sweat Test for Detection of Cystic Fibrosis

For quite some time now, the sweat test has remained as a gold standard for diagnosing cystic fibrosis. This test must always be conducted by experienced and accredited laboratory personnel in specific health centers that perform at least 50 sweat tests annually. The test needs to be repeated at least two times if diagnosis is not fully supported or confirmed by genotyping.

Sweat tests are usually performed in newborn infants a week after birth. Follow up tests could be conducted in the succeeding days. It should be a routine to perform the test in infants within 2 weeks after delivery if they weigh more than 3 kilograms (6.6 pounds).

In the procedure, sweat should immediately be collected within 30 minutes. Preferred sites for sweat collection are the forearm, chest, back, and thigh. The doctor would rub a minimal amount of sweat-producing solution on the target skin. A minor amount of electrical current would be applied to the skin patch to induce sweating. Do not worry about the pain because the procedure is guaranteed to not hurt significantly. It would only cause warm or tingling sensation. All the while, the skin patch would be covered with plastic and gauze for easy collection of sweat within 30 minutes. The sample of sweat taken would be immediately taken to the lab for testing.

Not all infants could be subjected to sweat testing. In particular, the test should be delayed or temporarily prevented in babies who are systematically unwell, underweight, and dehydrated. Infants with cutaneous rashes in the target simulation site should also be temporarily spared. There are cases wherein sweat tests yield false positive results. In those cases, patients could be under certain medications. That is the real reason why secondary or repeat sweat tests are recommended as well.

By: Didier De Coster

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