The Cytosponge-TFF3 test has been evaluated among more than 2000 patients in two clinical settings,12 13 proving its safety, cost-effectiveness and accuracy as a potential test for BO.14–17 The large (N>13 000), pragmatic, randomised, controlled BEST3 trial was recently conducted in primary care in England18 and demonstrated that offer of the Cytosponge test to individuals on medication for recurrent reflux symptoms identified ten times more cases of BO than usual care. This evidence concerns the gene TFF3 and bronchiolitis obliterans syndrome.