Alfin G. Vicencio, MD Attending in Pediatric Pulmonary, Steven and Alexandra Cohen Childrens Med Center, explains newborn screening may not be as surefire shot to diagnose CF as thought.
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Newborn Screening and Diagnosis of Cystic Fibrosis Male: Unfortunately, we have newborn screening, and we get some false positives, and I get calls. It always happens on a Friday afternoon. We found out that the cystic fibrosis screen is abnormal. Does that mean you automatically have cystic fibrosis if that cyst back saying that, “Oh, you got to do further testing”? Dr. Alfin Vicencio: No, of course not. The false positive rate is actually fairly high. Over the past ten years, here in New York City -- in the New York City area, there have been studies that showed that the false positive rate is relatively high. It’s not something that one should immediately jump to the conclusion that your child has cystic fibrosis. If they demonstrated any persistent respiratory symptoms or gastrointestinal symptoms then further testing might be oriented. Male: We’re probably going to do testing anyway because the parents are going to have a nervous breakdown, but if you look at a baby, you had full term, stools are normal, breathing comfortably, you're not too worried at that particular point, is that true? Dr. Alfin Vicencio: Yes, that’s true. Male: And, we tell them it could be but if it’s probably something mild but if the baby is having frothy stools, maybe gets attached in pneumonia early, red flag, is that correct. Dr. Alfin Vicencio: Yes, absolutely. Male: What would you do to make them properly diagnosed? What test would be the best test to cystic fibrosis? Dr. Alfin Vicencio: Right now, the sweat test is still the -- Male: Would you explain what a sweat test is? Dr. Alfin Vicencio: In cystic fibrosis, there is an abnormal transport of electrolytes particularly chloride that contributes to a lot of repeating infections in the lungs, and this defect is actually present throughout the body so that when you collect sweat from the skin and analyze that, if there is an abnormally high level of chloride in the sweat then that’s -- Male: What would be the number if you see this kid has probably has cystic fibrosis? What would be the measure? Dr. Alfin Vicencio: Above 60. Male: Above 60. What about if it’s 40 to 60, grey zone? Dr. Alfin Vicencio: 40 to 60 is a grey zone. It’s what we call a borderline sweat test, and in those cases, rigid testing is indicated as well as genetic testing. These days, there are, well, over 2,000 genetic mutations that contribute to cystic fibrosis, and a lot of those cause milder disease and possibly borderline sweat test.

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