by Stephen C. Pelsue, Ph.D.
Mon, Jun 1st, 2026 9:41 am
Cystic fibrosis (CF) is a life‑limiting autosomal recessive disease caused by pathogenic variants in the CFTR gene on chromosome 7, which encodes an epithelial chloride channel.[1–4] Defective CFTR leads to dehydrated, viscous secretions that obstruct small ducts and airways, driving chronic lung infection, exocrine pancreatic insufficiency, malnutrition, male infertility, and multi‑organ complications.[2–5] To develop CF, a child must inherit two disease‑causing CFTR variants (one from each parent); heterozygous carriers are typically asymptomatic but can transmit the variant to offspring.[4–6] More than 2,000 CFTR variants have been described, with over 1,000 now interpreted as CF‑causing or clinically relevant, contributing to wide phenotypic variability from classic, early‑onset lung disease to milder CFTR‑related disorders.[1,3,4,7] In the United States, CF is among the most common life-shortening inherited disorders in people of European ancestry, affecting approximately 1 in 2,500–3,500 newborns, while occurring less frequently in Black and Asian American populations.[1,8–11]
Newborn screening (NBS) is critical because early diagnosis enables timely pancreatic enzyme replacement, nutritional support, infection prevention, and CFTR modulator therapy, which together improve growth, lung function, hospitalization rates, and long‑term survival.[1,7,10,12–14] Studies comparing screened versus clinically diagnosed cohorts consistently show better anthropometric outcomes, fewer pulmonary exacerbations, and lower healthcare costs when CF is identified in the first months of life.[1,7,10,12–14]
For decades, most CF NBS programs relied on IRT‑plus‑DNA algorithms built around panels dominated by variants common in individuals of European or Ashkenazi Jewish ancestry.[1,5,6] The classic F508del‑only or ACMG‑23‑variant approaches delivered good sensitivity in those groups but systematically underdetected CF in African American, Hispanic, Asian, and mixed‑ancestry infants.[1,8,9,11] By 2010, all 50 U.S. states and D.C. had implemented CF newborn screening. Yet, the underlying molecular tests still encoded an ancestry bias that translated into delayed diagnoses and missed cases in non‑European populations.[1,11,14]
In April 2025, the Cystic Fibrosis Foundation (CFF) published the first evidence‑based consensus guideline for CF newborn screening in the International Journal of Neonatal Screening, based on a systematic review of diagnostic performance, timeliness, and equity.[1,16] The document contains seven core recommendations that, together, push programs decisively toward comprehensive CFTR2‑based variant coverage and sequencing.[1]
Notes to keep paragraph layout uniform: Notably, the recommendation for dual notification of both primary care providers and CF specialists for abnormal results reduces communication gaps, accelerates confirmatory testing, and improves family counseling.[1,2] Taken together, these recommendations formalize an equity requirement of ≥95% detection sensitivity in all ancestral groups, rather than treating equity as an aspirational goal.[1,11,13,16]
However, the shift to sequencing only improves equity if quality control (QC) keeps pace. Many validation datasets and control materials historically over‑represent variants common in European populations and under‑represent population‑specific variants located in technically challenging genomic contexts.[1,3,9] CFTR control panels that include a broad spectrum of SNVs, indels, homopolymers, and geographically enriched variants are essential to demonstrate uniform analytical performance across ancestries.[1,3,9] Equally important, bioinformatics pipelines must avoid ancestry‑biased decisions (such as allele‑frequency filters tuned to European datasets alone) that can systematically down‑call rare but pathogenic variants in underrepresented groups [1,3,4,9].
From a broader perspective, CF NBS has evolved over roughly 45 years from unreliable meconium tests to IRT‑based screening, from single‑variant DNA tiers to CFTR2‑informed multi‑variant panels, and now toward comprehensive sequencing [1,2,7,10,14]. The 2025 guideline codifies a new standard: not just early diagnosis, but early diagnosis delivered with equivalent sensitivity for every newborn, regardless of ancestry.[1,11,13,14,16] Building sequencing pipelines and QC systems that embody that standard is now one of the most important tasks facing molecular diagnostics professionals working in newborn screening.[1–4,7–9,11–15,16]
Stephen C. Pelsue, Ph.D. is the Manager of Discovery for Maine Molecular Quality Controls, Inc (MMQCI) in Saco, Maine. MMQCI develops and delivers high-quality nucleic acid controls for molecular diagnostics and precision medicine. Previously Stephen was the Scientific Director at BBI Solutions, a global leader in providing critical reagents and custom development for the In Vitro Diagnostic market. Prior to joining BBI Solutions, he was a Faculty member at the University of Southern Maine, in the Applied Medical Sciences Department. During his tenure there he served as Department Graduate Coordinator, Department Chair, and Associate Dean of the College of Science, Technology, and Health.
Stephen received his B.S. in Chemistry from Northland College (Ashland, WI) and Ph.D. (Biochemistry) from North Carolina State University (Raleigh, NC), followed by a post-doctoral Fellowship at The Jackson Laboratory (Bar Harbor, ME).
Stephen C. Pelsue, Ph.D.
