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Cystic fibrosis diagnosis

Created by Amy Fan.

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Video transcript

- [Voiceover] The gold standard for diagnosing Cystic Fibrosis is called the Sweat Test. Now it's not where you have to exercise a lot and sweat a lot, but the sweat is used to analyze how much chloride is in there. So the point of this whole test is how much chloride. And an abnormally high chloride points to Cystic Fibrosis. A lot of times this test is done in babies and for full-term babies actually age two to four weeks you can already have an accurate test. And the reason why they might get one or the doctor might order one is for example, if they have a genetic reason to maybe have CF, their parents carry the gene or they could have an abnormal newborn screen. Now every baby who is born in the hospital gets a newborn screen. They test for metabolic factors, things that can potentially point to CF and if they have something abnormal there they usually get the Sweat Test. So it's a test that we do if we suspect CF. And the way it's done is actually very simple. The baby or the person doesn't really even have to move. So first we apply a solution to the skin, wherever the area we're testing, which encourages it to make sweat. And then we take two electrodes, one positive, one negative, put it on the skin, turn on the current and this current stimulates the sweat glands. So if this is the skin, back here is the sweat gland. So after it is stimulated to make sweat we then collect it, send it to the lab and see how much chloride there is. That is the Sweat Test. Of course you can always go for genetic testing, right to the source of the gene. We already know what the gene is, and remember it's CFTCR. A thing to remember about this is that even though this is the gene that causes the disease there are many variations between people who have CF who have different variants of it, so it's not always as cut and dry, but for the most part analyzing this gene, seeing if it's normal can diagnose the CF. The Sweat Test and genetic testing are more or less answering a yes or no question, but to ask that question at the appropriate time there are diagnostic clues that we should look for in people who might not know that they have CF. So for people who work with kids when they're even just babies it's important to watch out for people who have failure to thrive, which just means they're not gaining weight and growing as they should. And the first thing you do is make sure the parents are feeding them correctly. But after that you start looking for what we call organic causes, or what's within the baby's metabolism that causes this, and CF is a big one. So failure to thrive, maybe it's good to do a Sweat Test. Or people who are having a lot of frequent, long infections, especially with bacteria or organisms that are not usually found in normal people. For example psuedomonas, this is something that thrives in the environment of the thick mucus that Cystic Fibrosis patients have in their lungs. So this is a type of pneumonia that's seen in a lot of CF patients, but not necessarily in people who don't have it, so this again should tip you off to look for the CF. Of course there's malnourishment, malnutrition I should say because they can eat all the food in the world, but if CF stops their pancreas from helping them digest it then they will have malnutrition. You can get things like a chest x-ray if you want to see the overinflated lungs. You can get abdominal x-ray in babies because CF can affect the intestines and sometimes it is visible on the film. But one thing, actually speaking of babies, that I want to point out is to watch out for babies who have delayed meconium. Not to gross you out, but meconium is the brown sludge that comes out of a baby when they're first born. It's kind of like their first poop, but it's not real poop because they haven't eaten yet, but if the sludge doesn't come out there are several reasons that could be and CF is one of the major reasons. So working with newborns if they don't pass meconium within the first few hours like normal babies do, it's worth it to look into that further and see if they possibly could have Cystic Fibrosis. Diagnosing CF is not really a huge mystery because we know the gene, we know the Sweat Test has a good accuracy, so the key in Cystic Fibrosis diagnosis is to watch out for these clues and think of CF when you see them.