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A 31-year-old member asked:

How frequent are false positives on cystic fibrosis tests?

1 doctor answer4 doctors weighed in
Dr. Brian Bezack
Pediatric Pulmonology 18 years experience
As high as 15%: The sweat chloride test is still the gold standard diagnostic test for cystic fibrosis. The accuracy of this test is highly dependent on the method used and the lab it is performed in. I only trust a result that is performed in a center that is certified by the cystic fibrosis foundation. Some reasons for false positives include: lab error, malnutrition, & eczema.
Dr. Amrita Dosanjh
Pediatric Pulmonology 36 years experience
I would also suggest this article on the topic: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1320177/
Dec 15, 2014

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A 48-year-old member asked:

How typical are false positives on cystic fibrosis tests?

2 doctor answers4 doctors weighed in
Dr. David Escobar
Dr. David Escobaranswered
Family Medicine 9 years experience
Not Typical: Certain rare conditions can also lead to high sweat chloride levels (the gold standard test for cystic fibrosis). However, these rare conditions (there's a list) will cause the patient to exhibit different symptoms than those consistent with cystic fibrosis, so the sweat chloride test is considered to be reliable in diagnosing CF in conjunction with the patient's history and physical exam.
CA
A 33-year-old member asked:

How common are false positives with cystic fibrosis tests?

3 doctor answers12 doctors weighed in
Dr. Robert Fink
Pediatrics 47 years experience
Uncommon: False positive sweat tests to diagnose CF are very uncommon. Genetic testing should never have false positive results. However, newborn screening for CF is frequently positive in babies who have one copy of the CF gene (cf carriers). A positive newborn screening for CF is not a diagnosis of CF unless the baby has a positive sweat test or positive genetic testing with two mutations identified.

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Last updated Apr 8, 2015
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