SCREENING FOR CYSTIC FIBROSIS: THE IMPORTANCE OF USING THE CORRECT TOOLS
AbstractBackground: Cystic Fibrosis (CF) is a potentially lethal genetic disorder. The most frequentmutation worldwide in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) geneis designated as the Delta F508 mutation. This mutation was found in only 33% of Pakistanipatients studied. Since the common Pakistani mutations remain to be identified, appropriatescreening tools are required to identify disease. Sweat chloride determinations remain the goldstandard for diagnosing CF. This study was done to emphasize the importance of using the correcttests. Methods: The study was conducted at the Aga Khan University Hospital. The CFTR deltaF508 mutation was tested on blood samples from patients suspected with CF. Sweat chlorideanalysis using pilocarpine iontopharesis was done with a positive value of greater than 60 meq/L.Results: 57 pediatric samples were screened for the delta F508 mutation and were positive in only10.6 % of all patients tested. 12/57 (21%) had a preliminary sweat test. 6/12 (50%) of thesepatients had an abnormal sweat test and 3/6 patients with an abnormal sweat chloride (50 %) haddeltaF508 mutations - 2/6 (33%) were homozygotes and 1 was a compound heterozygote. Since79% did not have a sweat test, it was difficult to assess whether this subset of patients had cysticfibrosis with a CFTR mutation other than the delta F508 tested or no CF. Conclusion: Sweatchloride analysis is critical to distinguish CF from other causes of severe pulmonary andpancreatic insufficiencies and to define patients requiring further analysis.Key words: Cystic fibrosis, sweat chloride, mutation analysis
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