Sweat chloride is not a useful marker of clinical response to Ivacaftor

Thorax. 2014 Jun;69(6):586-7. doi: 10.1136/thoraxjnl-2013-204532. Epub 2013 Nov 20.


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.

Keywords: Cystic Fibrosis.

Publication types

  • Letter
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminophenols / economics
  • Aminophenols / therapeutic use*
  • Biomarkers / analysis
  • Body Height
  • Body Weight
  • Chlorides / analysis*
  • Cohort Studies
  • Cystic Fibrosis / drug therapy*
  • Cystic Fibrosis / genetics
  • Cystic Fibrosis / physiopathology
  • Forced Expiratory Flow Rates
  • Humans
  • Lung / physiopathology
  • Prospective Studies
  • Quinolones / economics
  • Quinolones / therapeutic use*
  • Spirometry
  • Sweat / chemistry*


  • Aminophenols
  • Biomarkers
  • Chlorides
  • Quinolones
  • ivacaftor