We believe that the data in this letter clearly demonstrate that even with CFTR2 expansion to 719 variants, striving to achieve equity of early diagnosis of CF via screening requires states to perform a sweat test in all infants with a high IRT level and one identified CFTR variant. This recommended policy can be debated but sweat testing overload should not be the argued as the barrier and CF specialists need to recognize that CFTR2 may never include all of the very rare, “private” pathogenic variants nor will next generation sequencing cover the structural variants such as deletions and duplications.

Background: Newborn screening (NBS) for cystic fibrosis (CF) has been underway universally in the USA for more than a decade, as well in most European countries, and algorithms have been evolving throughout this period with quality improvement projects as immunoreactive trypsinogen determinations alone have been transformed to a 2-tier strategy with DNA analyses. Objective: To apply next generation sequencing (NGS) as a method for expanding the DNA tier for identifying variants in the cystic fibrosis transmembrane conductance regulator ( CFTR) gene with minimization of unintended outcomes. Design: Sequential quality improvement project in three phases using plan coupled to statewide follow up and analysis of screening outcomes in comparison to other NBS programs that use CFTR sequencing. Results: After demonstrating feasibility in the first phase, we studied an IRT/NGS algorithm that included CFTR Variants with Varying Clinical Consequences (VVCCs). This revealed a high identification of CF patients with 2-variants detected through screening, but for every CF case there were 1.4 with cystic fibrosis metabolic syndrome/cystic fibrosis screen positive, inconclusive diagnosis (CRMS/CFSPID). This led us to a third phase of quality improvement in which the VVCCs were eliminated except for R117H, resulting in 94% 2-variant detection of patients and 0.44:1 ratio of CRMS/CFSPID to CF. Conclusion: NGS can be used with IRT as an effective method of identifying infants at risk for CF without an appreciable increase in detection of either carriers or CRMS/CFSPID cases.