In this study, we hypothesised that immunoreactive trypsinogen (IRT) levels, used in NBS as a marker of pancreatic disease and function, may reflect the degree of CFTR dysfunction in each individual and therefore would help to identify those with CRMS/CSPID who are later at risk for meeting the criteria of CF. This evidence concerns the gene CFTR and CFTR-related metabolic syndrome/CF screen positive, inconclusive diagnosis.