CFTR and cystic fibrosis: If neonatal screening indicates positivity, yet the patient lacks indicative disease symptoms, and the sweat test yields either negative results with two CFTR mutations, one of which carries ambiguous phenotypic implications, or equivocal outcomes with 0–1 CF-causing mutations, the individual may be categorized as having CFTR-related metabolic syndrome (CRMS) in the USA or CF screen positive, inconclusive diagnosis (CFSPID) in Europe [27].