A Prospective Study of Advanced Diagnostics in People With an Unclear Diagnosis of Cystic Fibrosis

Sometimes it is very difficult to tell if someone has cystic fibrosis (CF), especially when they have rare CF genes. Without this certainty, they are unlikely to get the correct treatment so their health may be affected. More accurate ways to test for CF are therefore needed in this situation. The aim of this study is to develop a more accurate test using what are called "organoids" or "mini organs." Organoids are grown in the laboratory from a small piece of gut tissue. As they have the person's exact genes, they can show if the CF gene ("CFTR") is working correctly or not and thus if the person has CF. The investigators will compare the organoid response with the current more established tests, such as the sweat test and CF genetics, and other recognised specialist tests called nasal potential difference (NPD) and intestinal current measurement (ICM). The gut tissue is usually taken by a quick, relatively painless, outpatient procedure (rectal biopsy). The additional benefit of organoids is that they can also help us to work out the best treatment for that individual by testing how well the gut tissue responds to different drugs in the laboratory. The investigators wish to carry out this research to prove that gut organoids are a better way to test for CF in this situation. The goal will be to diagnose people faster and for them to get better treatment quicker, both key for leading a longer and healthier life.