title: Sweat chloride is not a useful marker of clinical response to Ivacaftor.
abstract: Clinical trials have revealed that Ivacaftor significantly reduces sweat chloride in patients with cystic fibrosis who carry the G551D mutation. This finding has been incorporated into the commissioning guidelines in the UK with a sweat chloride reduction of 30% or below 60 mmol/L, specified as the main criteria for continued funding of Ivacaftor for individual patients. In a cohort of 24 adults who were prescribed Ivacaftor, there was no correlation between absolute or relative reductions in sweat chloride and improvements in lung function. This questions the validity of sweat chloride as a surrogate marker of clinical efficacy.
authors.affiliation: Manchester Adult Cystic Fibrosis Centre, University Hospital of South Manchester, Manchester, UK;
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barry
authors.affiliation: Manchester Adult Cystic Fibrosis Centre, University Hospital of South Manchester, Manchester, UK; Institute of Inflammation and Repair, University of Manchester, Manchester, UK.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
authors.affiliation: Manchester Adult Cystic Fibrosis Centre, University Hospital of South Manchester, Manchester, UK; Institute of Inflammation and Repair, University of Manchester, Manchester, UK.
authors.forename: Anthony K
authors.initials: AK
authors.lastname: Webb
authors.affiliation: Manchester Adult Cystic Fibrosis Centre, University Hospital of South Manchester, Manchester, UK; Institute of Inflammation and Repair, University of Manchester, Manchester, UK.
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Horsley
mesh_terms: D000627:Aminophenols / Q000191:economics / Q000627:therapeutic use*; D015415:Biomarkers / Q000032:analysis; D001827:Body Height; D001835:Body Weight; D002712:Chlorides / Q000032:analysis*; D015331:Cohort Studies; D003550:Cystic Fibrosis / Q000188:drug therapy* / Q000235:genetics / Q000503:physiopathology; D005540:Forced Expiratory Flow Rates; D006801:Humans; D008168:Lung / Q000503:physiopathology; D011446:Prospective Studies; D015363:Quinolones / Q000191:economics / Q000627:therapeutic use*; D013147:Spirometry; D013542:Sweat / Q000737:chemistry*
chemical_list: D000627:Aminophenols; D015415:Biomarkers; D002712:Chlorides; D015363:Quinolones; C545203:ivacaftor
keywords: Cystic Fibrosis