Finally, the growing proportion of NBS programs revealed a large number of infants having a Cystic Fibrosis Screen Positive, Inconclusive Diagnosis (CFSPID) in Europe or CFTR – related metabolic syndrome (CRMS) in the US including those infants with elevated IRT levels, but with insufficient sweat chloride or genetic data to support a diagnosis of CF [15, 16]. Here, CFTR is linked to cystic fibrosis.