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A new sweat test determines the ratio between two types of a person's sweat by using dyes to form bubbles on the skin. That ratio accounts for differences in sweat volume—between a conditioned athlete and a sedentary person, for example—and reveals an individual's CFTR levels. (Credit: torbakhopper/Flickr)

cystic fibrosis

Sweat test may lead to better cystic fibrosis therapy

A new sweat test for cystic fibrosis provides more detailed information than current tests and may lead to new treatments for the disease.

The test shows that smaller amounts of a particular protein are necessary to stop cystic fibrosis symptoms than previously thought.

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“I was amazed it worked out as well as it did,” says Jeffrey Wine, a professor of psychology and biology who is the director of the Cystic Fibrosis Research Laboratory at Stanford University.

Wine and colleagues described the test in October in the journal PLOS ONE. Since then, they have used the test to measure protein levels in patients taking a cystic fibrosis drug. The latest findings also are published in PLOS ONE.

Cystic fibrosis is a recessive genetic disorder that disables a key protein, called the cystic fibrosis transmembrane conductance regulator, or CFTR, that is responsible for transferring fluid and minerals in and out of cells.

The effect on the 30,000 Americans diagnosed with the condition is debilitating. Patients suffer from chronic lung infections, male sterility, and a host of other symptoms. In the past, carriers struggled to survive past infancy.

Doctors usually treat cystic fibrosis by tackling symptoms as they appear. Very few drugs target the underlying problem: a patient’s CFTR is broken, damaged, or missing. Defects vary greatly: the entire protein might be missing, or it could have just a few flaws. Current tests, which measure the amount of chloride in sweat, can’t precisely identify how much functioning CFTR is present.

A lower target

The new test determines the ratio between two types of a person’s sweat by using dyes to form bubbles on the skin. That ratio accounts for differences in sweat volume—between a conditioned athlete and a sedentary person, for example—and reveals an individual’s CFTR levels.

The work shows that even healthy people have varying levels of CFTR and that only a small amount of CFTR is needed to remain disease-free.

“The biggest surprise for me was how small the response was. I don’t think anybody expected that,” Wine says.

Therefore, drug developers have a lower target: they only need to restore 10 percent of CFTR functionality to relieve symptoms. Also, patients can be treated with drugs that supplement their personal CFTR levels to relieve symptoms.

That is particularly important because people with the same genetic flaw can have different amounts of CFTR, Wine says.

For the study, researchers examined the CFTR levels in eight subjects with cystic fibrosis. Six of the patients were taking ivacaftor, a drug currently available to treat some types of cystic fibrosis. Ivacaftor boosted CFTR levels as expected, but it also increased CFTR levels in a type of cystic fibrosis it is not currently designed to treat, Wine says.

Next, the researchers plan to examine differences in CFTR in healthy individuals and hopes to eventually determine the precise amount of CFTR needed to alleviate symptoms.

Source: Stanford University

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