Moreover, the recently implemented extensive newborn screening programs identify increasing numbers of asymptomatic CF patients merely identified by elevated serum concentrations of immunoreactive trypsinogen (IRT), posing new challenges to the CF diagnosis paradigm [8], [15], [16], especially when associated with borderline sweat [Cl−] and/or inconclusive CFTR genotypes [10], [11], [15], [16]. The gene discussed is CFTR; the disease is cystic fibrosis.