Thursday, October 3, 2019

Cystic Fibrosis Newborn Screening

Cystic Fibrosis Newborn Screening Cystic fibrosis is a common autosomal recessive genetic disorder1. This means that to have cystic fibrosis, a person must have inherited a defective gene from each of his or her parents2. This gene is located on chromosome seven2. Absence or mutation in this particular gene results in worse performance or absence of the Cystic Fibrosis Transmembrane Conductance Regulator2. This is most commonly found in Europe, North America, and Australia1. This gene manages anion transport and mucociliary clearance in the airways1. With the failure of this function, the results are mucus retention and chronic infection in the lungs1. Nowadays, modern technology provides aid for patients with their diseases and gives them a longer and more active life. Newborn screening for cystic fibrosis is a modern technological advance which is designed to detect early signs of cystic fibrosis. Several methods under the name of the Newborn Screening are used to detect whether a newborn has cystic fibrosis or not1. These methods include immunoreactive trypsinogen (IRT) testing combined with DNA mutation analysis and the sweat chloride test1. IRT stands for Immunoreactive Trypsinogen Test. The procedure of this test is a chemical reaction. Trypsinogen is made from the pancreas, and it normally transmits to the intestines where it is activated to a form of an enzyme called trypsin. In a patient who has cystic fibrosis, the thick mucus covers the pancreatic ducts1. Therefore, trypsinogen wont reach the intestines, and the amount of trypsinogen goes up. This test runs with a blood sample, and if the results come out with a normal level of trypsinogen, then this test is reliable, but if there is a high level of trypsinogen, then more tests need to be run to find out whether the patient has cystic fibrosis or not. A sweat chloride test is the amount of chloride in patients sweat. In a patient that has Cystic Fibrosis, the sweat chloride test will result in significantly higher levels of chloride in sweat than a person that does not have cystic fibrosis due to the restricted movement of chloride. The gene mutation test is a DNA sequencing test to locate a defective gene in the chromosome. There are many different types of mutations that can cause a deficiency in the production of the CFTR protein. More than 2000 CFTR variants have been discovered1. About 15% of the identified gene variants are not associated with CF1. CFTR mutations can be classified into six classes according to their effects on protein function1. Classification is helpful because it relates to the molecular and cellular processes in gene translation and protein processing and has some useful clinical relations1. Class I, II, and III mutations are associated with no residual CFTR function and patients with these mutations on average have a severe phenotype, whereas individuals with class IV, V, and VI mutations have some residual function of CFTR protein and have a mild lung phenotype and pancreatic deficiency1. Today, different laboratories use a wide variety of panels depending on the patients need, like t he twenty-three panel or panel of seventy. The following is an example of a molecular CF test. Lab Corporation of America published a procedure for a Cystic Fibrosis molecular diagnostic3; The coding sequence of CFTR is amplified by polymerase chain reaction and each PCR product (amplicon) then sequenced bi-directionally, using Sanger sequencing methodology. CFTR Chr7(q31,2) Nucleotide Change Amino Acid Change Consequencing Zygosity Relation to Cystic Fibrosis c.1327G>T p.Asp443Tyr missense mutation homozygous recessive, associated 1. Prof J Stuart Elbom, Cystic Fibrosis, Lancet, 19-25 November 2016, Volume 388, Issue 10059, page 2519-2531 2. The Clinical and Functional Translation of CFTR(CFTR2) at Copyright 2011 US CF Foundation, John Hopkins University The Hospital for Sick Children; available at 3. Corporation of America Published Documents   2014   available @ Center/Sample Reports/C-4/Cystic Fibrosis (CF) CFTR 252763.pdf

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