Diagnosis of Cystic Fibrosis in Screened Populations

Objective Cystic fibrosis (CF) can be difficult to diagnose, even when newborn screening (NBS) tests yield positive results. This challenge is exacerbated by the multitude of NBS protocols, misunderstandings about screening vs diagnostic tests, and the lack of guidelines for presumptive diagnoses. There is also confusion regarding the designation of age at diagnosis. Study design To improve diagnosis and achieve standardization in definitions worldwide, the CF Foundation convened a committee of 32 experts with a mission to develop clear and actionable consensus guidelines on diagnosis of CF with an emphasis on screened populations, especially the newborn population. A comprehensive literature review was performed with emphasis on relevant articles published during the past decade. Results After reviewing the common screening protocols and outcome scenarios, 14 of 27 consensus statements were drafted that apply to screened populations. These were approved by 80% or more of the participants. Conclusions It is recommended that all diagnoses be established by demonstrating dysfunction of the CF transmembrane conductance regulator (CFTR) channel, initially with a sweat chloride test and, when needed, potentially with newer methods assessing membrane transport directly, such as intestinal current measurements. Even in babies with 2 CF-causing mutations detected via NBS, diagnosis must be confirmed by demonstrating CFTR dysfunction. The committee also recommends that the latest classifications identified in the Clinical and Functional Translation of CFTR project [http://www.cftr2.org/index.php] should be used to aid with CF diagnosis. Finally, to avoid delays in treatment, we provide guidelines for presumptive diagnoses and recommend how to determine the age of diagnosis

Guidelines for Diagnosis of Cystic Fibrosis in Newborns through Older Adults: Cystic Fibrosis Foundation Consensus Report

Newborn screening (NBS) for cystic fibrosis (CF) is increasingly being implemented and is soon likely to be in use throughout the United States, because early detection permits access to specialized medical care and improves outcomes. The diagnosis of CF is not always straightforward, however. The sweat chloride test remains the gold standard for CF diagnosis but does not always give a clear answer. Genotype analysis also does not always provide clarity; more than 1500 mutations have been identified in the CF transmembrane conductance regulator (CFTR) gene, not all of which result in CF. Harmful mutations in the gene can present as a spectrum of pathology ranging from sinusitis in adulthood to severe lung, pancreatic, or liver disease in infancy. Thus, CF identified postnatally must remain a clinical diagnosis. To provide guidance for the diagnosis of both infants with positive NBS results and older patients presenting with an indistinct clinical picture, the Cystic Fibrosis Foundation convened a meeting of experts in the field of CF diagnosis. Their recommendations, presented herein, involve a combination of clinical presentation, laboratory testing, and genetics to confirm a diagnosis of CF

Newborn Sequencing in Genomic Medicine and Public Health

The rapid development of genomic sequencing technologies has decreased the cost of genetic analysis to the extent that it seems plausible that genome-scale sequencing could have widespread availability in pediatric care. Genomic sequencing provides a powerful diagnostic modality for patients who manifest symptoms of monogenic disease and an opportunity to detect health conditions before their development. However, many technical, clinical, ethical, and societal challenges should be addressed before such technology is widely deployed in pediatric practice. This article provides an overview of the Newborn Sequencing in Genomic Medicine and Public Health Consortium, which is investigating the application of genome-scale sequencing in newborns for both diagnosis and screening

Implementation of Hospital-Based Supplemental Duchenne Muscular Dystrophy Newborn Screening (sDMDNBS): A Pathway to Broadening Adoption

Duchenne muscular dystrophy (DMD) is not currently part of mandatory newborn screening, despite the availability of a test since 1975. In the absence of screening, a DMD diagnosis is often not established in patients until 3–6 years of age. During this time, irreversible muscle degeneration takes place, and clinicians agree that the earlier therapy is initiated, the better the long-term outcome. With recent availability of FDA-approved DMD therapies, interest has renewed for adoption by state public health programs, but such implementation is a multiyear process. To speed access to approved therapies, we implemented a unique, hospital-based program offering parents of newborns an optional, supplemental DMD newborn screen (NBS) via a two-tiered approach: utilizing a creatine kinase (CK) enzyme assay coupled with rapid targeted next-generation sequencing (tNGS) for the DMD gene (using a Whole-Exome Sequencing (WES) assay). The tNGS/WES assay integrates the ability to detect both point mutations and large deletion/duplication events. This tiered newborn screening approach allows for the opportunity to improve treatment and outcomes, avoid the diagnostic delays, and diminish healthcare disparities. To implement this screening algorithm through hospitals in a way that would ultimately be acceptable to public health laboratories, we chose an FDA-approved CK-MM immunoassay to avoid the risks of false-negative/-positive results. Because newborn CK values can be affected due to non-DMD-related causes such as birth trauma, a confirmatory repeat CK assay on a later dried blood spot (DBS) collection has been proposed. Difficulties associated with non-routine repeat DBS collection, including the tracking and recall of families, and the potential creation of parental anxiety associated with false-positive results, can be avoided with this algorithm. Whereas a DMD diagnosis is essentially ruled out by the absence of detected DMD sequence abnormalities, a subsequent CK would still be warranted to confirm resolution of the initial elevation, and thus the absence of non-DMD muscular dystrophy or other pathologies. To date, we have screened over 1500 newborns (uptake rate of ~80%) by a CK-MM assay, and reflexed DMD tNGS in 29 of those babies. We expect the experience from this screening effort will serve as a model that will allow further expansion to other hospital systems until a universal public health screening is established

Neonatal Genomics: Part 2—Applications

The next-generation sequencing techniques described in Part 1 of this review can be used to sequence single genes, panels of genes, whole exomes, or whole genomes. These tests can be used for both diagnostic and screening purposes in the newborn nursery and NICU. As the cost and turnaround time for genetic testing decrease, the use of sequencing data will become more prevalent and can influence the diagnostic evaluation and care of the newborn. The use of genomic data for newborn screening is more controversial but also has potential usefulness in expanding the capabilities of current, predominantly analyte-based newborn screening algorithms. The incorporation of genomic information into the care of well newborns and ill NICU patients raises important ethical concerns that will need to be addressed as whole exome and whole genome sequencing become more routinely performed.</jats:p

Neonatal Genomics: Part 1—Basics and Definitions

As genomic medicine is increasingly incorporated into clinical practice across all disciplines, an understanding of basic genetic concepts is important for the neonatologist. There are many different ways in which variations in the human genetic sequence, which comprises the genome, can lead to disease. Gene sequencing through the use of Sanger sequencing or next-generation sequencing technology can detect disease-causing variants and can be performed across the entire human genome in whole genome sequencing or across only the coding regions of the human genome in whole exome sequencing.</jats:p