Genomic sequencing in cystic fibrosis newborn screening: what works best, two-tier predefined CFTR mutation panels or second-tier CFTR panel followed by third-tier sequencing?

Diagnostic Transitions of Cystic Fibrosis and Related Metabolic Syndrome Compared After 12 Years of Newborn Screening in California

OBJECTIVE

To compare the long-term diagnostic transitions for cystic fibrosis (CF) and CF-Related Metabolic Syndrome (CRMS) side-by-side during follow-up since the onset of newborn screening in California.

STUDY DESIGN

Using real-world data, we conducted a retrospective cohort study to compare long-term observations of CRMS and CF in California and the diagnostic transitions from one to the other using clinical and diagnostic metrics. The California Genetic Disease Screening Program (GDSP) newborn screening for CF employs an immunoreactive trypsinogen tier-1 laboratory test, followed by molecular testing. This approach captures CF and CRMS, a diagnosis of "watchful waiting" among infants at risk for CF but with signs and symptoms that may emerge outside the screening window. Waiting entails periodic diagnostic reviews that can continue for many years; GDSP routinely conducts five years of follow-up for each child identified with a disorder. We utilized categorial logistic regression to compare the transitions with CRMS.

RESULTS

After screening 5,944,700 newborns between July 2007 and July 2019, 694 CF cases and 1,258 CRMS cases were identified. Of the 1,258 CRMS cases, 66 (5.2%, 95% CI=3.9%,6.4%) transitioned from CRMS to CF (CRMS2CF) at a mean age of 3.3 years (median=2.9 years). CRMS2CF cases had longer follow-up periods and were more likely later to develop positive sweat chloride and fecal elastase test results after 6 months of life than other CRMS cases.

CONCLUSION

These results suggest that children who have a CRMS2CF transition are more likely to develop positive biochemical markers than other CRMS patients and have few clinical indications during the first five years of follow-up.

Improved detection of cystic fibrosis by the California Newborn Screening Program for all races and ethnicities

BACKGROUND

Newborn screening (NBS) for cystic fibrosis (CF) is universal in the United States. Protocols vary but include an immunoreactive trypsinogen (IRT) level and CFTR variant panel. California CF NBS has a 3-step screening: IRT level, variant panel, and CFTR sequencing if only one variant identified on panel.

METHODS

This was a cohort study of infants with CF born in California (2007-2021) to examine racial and ethnic differences in having a false-negative NBS result for CF and at which step the false-negative occurred. We examined how different CFTR variant panels would improve detection of variants by race and ethnicity: original 39-variant panel, current 75-variant panel, and all 402 disease-causing CFTR variants in the CFTR2 database.

RESULTS

Of the 912 infants born in California with CF, 84 had a false-negative result: 38 due to low IRT level and 46 with a high IRT value (but incomplete variant detection). Asian (OR 6.3) and Black infants (OR 2.5) were more likely to have a false-negative screening result than non-Hispanic white infants. The majority of false-negative screening (but CF diagnosis) cases among American Indian/Native Alaskan and non-Hispanic White infants were due to low IRT levels. The majority of Asian and Hispanic infants with false-negative screening had no variants detected. Detection of two CFTR variants was improved with the 75-variant panel in Black, Hispanic, and non-Hispanic White infants and with the 402-variant panel in Black, Hispanic, non-Hispanic White, and other race infants.

CONCLUSIONS

Larger CFTR panels in NBS improved the detection of CF in all races and ethnicities.

Racial inequities and rare CFTR variants: Impact on cystic fibrosis diagnosis and treatment

Cystic fibrosis (CF) has been traditionally viewed as a disease that affects White individuals. However, CF occurs among all races, ethnicities, and geographic ancestries. The disorder results from mutations in the CF transmembrane conductance regulator (CFTR). Varying incidence of CF is reported among Black, Indigenous, and People of Color (BIPOC), who typically exhibit worse clinical outcomes. These populations are more likely to carry rare CFTR variants omitted from newborn screening panels, leading to disparities in care such as delayed diagnosis and treatment. In this study, we present a case-in-point describing an individual of Gambian descent identified with CF. Patient genotype includes a premature termination codon (PTC) (c.2353C>T) and previously undescribed single nucleotide deletion (c.1970delG), arguing against effectiveness of currently available CFTR modulator-based interventions. Strategies for overcoming these two variants will likely include combinations of PTC suppressors, nonsense mediated decay inhibitors, and/or alternative approaches (e.g. gene therapy). Investigations such as the present study establish a foundation from which therapeutic treatments may be developed. Importantly, c.2353C>T and c.1970delG were not detected in the patient by traditional CFTR screening panels, which include an implicit racial and ethnic diagnostic bias as these tests are comprised of mutations largely observed in people of European ancestry. We suggest that next-generation sequencing of CFTR should be utilized to confirm or exclude a CF diagnosis, in order to equitably serve BIPOC individuals. Additional epidemiologic data, basic science investigations, and translational work are imperative for improving understanding of disease prevalence and progression, CFTR variant frequency, genotype-phenotype correlation, pharmacologic responsiveness, and personalized medicine approaches for patients with African ancestry and other historically understudied geographic lineages.

Newborn screening for Duchenne muscular dystrophy: A two-year pilot study

OBJECTIVE

Duchenne muscular dystrophy (DMD) is an X-linked disorder resulting in progressive muscle weakness and atrophy, cardiomyopathy, and in late stages, cardiorespiratory impairment, and death. As treatments for DMD have expanded, a DMD newborn screening (NBS) pilot study was conducted in New York State to evaluate the feasibility and benefit of NBS for DMD and to provide an early pre-symptomatic diagnosis.

METHODS

At participating hospitals, newborns were recruited to the pilot study, and consent was obtained to screen the newborn for DMD. The first-tier screen measured creatine kinase-MM (CK-MM) in dried blood spot specimens submitted for routine NBS. Newborns with elevated CK-MM were referred for genetic counseling and genetic testing. The latter included deletion/duplication analysis and next-generation sequencing (NGS) of the DMD gene followed by NGS for a panel of neuromuscular conditions if no pathogenic variants were detected in the DMD gene.

RESULTS

In the two-year pilot study, 36,781 newborns were screened with CK-MM. Forty-two newborns (25 male and 17 female) were screen positive and referred for genetic testing. Deletions or duplications in the DMD gene were detected in four male infants consistent with DMD or Becker muscular dystrophy. One female DMD carrier was identified.

INTERPRETATION

This study demonstrated that the state NBS program infrastructure and screening technologies we used are feasible to perform NBS for DMD. With an increasing number of treatment options, the clinical utility of early identification for affected newborns and their families lends support for NBS for this severe disease.

Expanding the Australian Newborn Blood Spot Screening Program using genomic sequencing: do we want it and are we ready?

Since the introduction of genome sequencing in medicine, the factors involved in deciding how to integrate this technology into population screening programs such as Newborn Screening (NBS) have been widely debated. In Australia, participation in NBS is not mandatory, but over 99.9% of parents elect to uptake this screening. Gauging stakeholder attitudes towards potential changes to NBS is vital in maintaining this high participation rate. The current study aimed to determine the knowledge and attitudes of Australian parents and health professionals to the incorporation of genomic sequencing into NBS programs. Participants were surveyed online in 2016 using surveys adapted from previous studies. The majority of parents (90%) self-reported some knowledge of NBS, with 77% expressing an interest in NBS using the new technology. This was significantly lower than those who would utilise NBS using current technologies (99%). Although, many health professionals (62%) felt that new technologies should currently not be used as an adjunct to NBS, 79% foresaw the use of genomic sequencing in NBS by 2026. However, for genomic sequencing to be considered, practical and technical challenges as well as parent information needs were identified including the need for accurate interpretation of data; pre-and post-test counselling; and appropriate parental consent and opt-out process. Therefore, although some support for implementing genomic sequencing into Australian NBS does exist, there is a need for further investigation into the ethical, social, legal and practical implications of introducing this new technology as a replacement to current NBS methods.

CFTR bearing variant p.Phe312del exhibits function inconsistent with phenotype and negligible response to ivacaftor

The chloride channel dysfunction caused by deleterious cystic fibrosis transmembrane conductance regulator (CFTR) variants generally correlates with severity of cystic fibrosis (CF). However, 3 adults bearing the common severe variant p.Phe508del (legacy: F508del) and a deletion variant in an ivacaftor binding region of CFTR (p.Phe312del; legacy: F312del) manifested only elevated sweat chloride concentration (sw[Cl-]; 87-105 mEq/L). A database review of 25 individuals with F312del and a CF-causing variant revealed elevated sw[Cl-] (75-123 mEq/L) and variable CF features. F312del occurs at a higher-than-expected frequency in the general population, confirming that individuals with F312del and a CF-causing variant do not consistently develop overt CF features. In primary nasal cells, CFTR bearing F312del and F508del generated substantial chloride transport (66.0% ± 4.5% of WT-CFTR) but did not respond to ivacaftor. Single-channel analysis demonstrated that F312del did not affect current flow through CFTR, minimally altered gating, and ablated the ivacaftor response. When expressed stably in CF bronchial epithelial (CFBE41o-) cells, F312del-CFTR demonstrated residual function (50.9% ± 3.3% WT-CFTR) and a subtle decrease in forskolin response compared with WT-CFTR. F312del provides an exception to the established correlation between CFTR chloride transport and CF phenotype and informs our molecular understanding of ivacaftor response.

Evaluating Differences in the Disease Experiences of Minority Adults With Cystic Fibrosis

Extensive research has demonstrated disparities in health outcomes and survival between non-Hispanic Caucasian (NHC) and non-Caucasian or Hispanic (minority) persons with cystic fibrosis (CF) in the United States (US). However, very little research has been done to explore the disease experiences of racial and ethnic minority persons with CF. Adult subjects with CF were approached for study participation and to characterize their experiential disease perceptions. Survey data were analyzed using Chi-Square tests and Mann-Whitney U-test for basic categorical and continuous variables, and Kruskal-Wallis one-way ANOVA using ranks for Likert scales. Minority persons reported significantly lower scores (more negative experience) when comparing themselves to others with CF (15.18 ± 2.89 vs 18.40 ± 3.18, P < .01), particularly in the areas of representation in research, experience, and support. We were able to identify the unique experiences of minority persons with CF, including perceived lower disease understanding and poorer representation compared to most others with CF. Further large studies are needed to develop and assess interventions that may be useful for serving these diverse populations.

Validation of a Custom Next-Generation Sequencing Assay for Cystic Fibrosis Newborn Screening

Newborn screening (NBS) for Cystic Fibrosis (CF) is associated with improved outcomes. All US states screen for CF; however, CF NBS algorithms have high false positive (FP) rates. In New York State (NYS), the positive predictive value of CF NBS improved from 3.7% to 25.2% following the implementation of a three-tier IRT-DNA-SEQ approach using commercially available tests. Here we describe a modification of the NYS CF NBS algorithm via transition to a new custom next-generation sequencing (NGS) platform for more comprehensive cystic fibrosis transmembrane conductance regulator (CFTR) gene analysis. After full gene sequencing, a tiered strategy is used to first analyze only a specific panel of 338 clinically relevant CFTR variants (second-tier), followed by unblinding of all sequence variants and bioinformatic assessment of deletions/duplications in a subset of samples requiring third-tier analysis. We demonstrate the analytical and clinical validity of the assay and the feasibility of use in the NBS setting. The custom assay has streamlined our molecular workflow, increased throughput, and allows for bioinformatic customization of second-tier variant panel content. NBS aims to identify those infants with the highest disease risk. Technological molecular improvements can be applied to NBS algorithms to reduce the burden of FP referrals without loss of sensitivity.

Primary care providers' role in newborn screening result notification for cystic fibrosis

OBJECTIVE

To explore primary care providers' (PCPs') role in result notification for newborn screening (NBS) for cystic fibrosis (CF), given that expanded NBS has increased the number of positive screening test results, drawing attention to the role of PCPs in supporting families.

DESIGN

Cross-sectional survey and qualitative interviews.

SETTING

Ontario.

PARTICIPANTS

Primary care providers (FPs, pediatricians, and midwives) who received a positive CF NBS result for an infant in their practice in the 6 months before the study.

MAIN OUTCOME MEASURES

Whether the PCP notified the family of the initial positive CF screening result.

RESULTS

Data from 321 PCP surveys (response rate of 51%) are reported, including 208 FPs, 68 pediatricians, and 45 midwives. Interviews were completed with 34 PCPs. Most (65%) surveyed PCPs reported notifying the infant's family of the initial positive screening result; 81% agreed that they have an important role to play in NBS; and 88% said it was important for PCPs, rather than the NBS centre, to notify families of initial positive results. With support and information from NBS centres, 68% would be extremely or very confident in doing so; this dropped to 54% when reflecting on their recent reporting experience. More than half (58%) of all PCPs said written point-of-care information from the NBS centre was the most helpful format. Adjusted for relevant factors, written educational information was associated with a lower rate of notifying families than written plus verbal information (risk ratio of 0.79; 95% CI 0.69 to 0.92). In the interviews, PCPs emphasized the challenge of balancing required content knowledge with the desire for the news to come from a familiar provider.

CONCLUSION

Most PCPs notify families of NBS results and value this role. These data are relevant as NBS programs and other genomic services expand and consider ways of keeping PCPs confident and actively involved.

Racially equitable diagnosis of cystic fibrosis using next-generation DNA sequencing: a case report

Background

Cystic Fibrosis (CF) is one of the most prevalent autosomal recessive inherited disease in Caucasians. Rates of CF were thought to be negligible in non-Caucasians but growing epidemiological evidence shows CF is more common in Indian, African, Hispanic, Asian, and other ethnic groups than previously thought. Almost all second-tier molecular diagnostic tools currently used to confirm the diagnosis of CF consist of panels of the most common CF-causing DNA variants in Caucasians. However non-Caucasian individuals with CF often have a different spectrum of pathogenic variants than Caucasians, limiting the clinical utility of existing molecular diagnostic panels in this group. As a consequence of racially inequitable CF testing frameworks, non-Caucasians with CF encounter greater delays in diagnosis and associated harms than Caucasians. An unbiased approach of detecting CF-causing DNA variants using full gene sequencing could potentially address racial inequality in current CF testing.

Case presentation

We present the case of a female baby from rural India who had a borderline first-tier newborn screening result for CF. Instead of choosing a targeted CF panel for second-tier testing, we used next-generation DNA sequencing to comprehensively analyze the cystic fibrosis transmembrane conductance regulator gene as an unbiased approach for molecular confirmation of CF. Sequencing identified two pathogenic variants that cause CF. One variant (c.1521_1523delCTT) is the most common cause of CF, while the other variant (c.870-1G > C) is absent from all population allele databases and has not been found in the Indian population previously. The rare variant would not have been detected by all currently available targeted CF panels used for second- or third-tier molecular CF testing.

Conclusions

Our use of full gene sequencing as a second-tier CF test in a non-Caucasian patient avoided the problems of missed diagnosis from using Caucasian-biased targeted CF panels currently recommended for second-tier testing. Full gene sequencing should be considered as the standard methodology of second-tier CF testing to enable equal opportunity for CF diagnosis in non-Caucasians.

Early Diagnosis and Intervention in Cystic Fibrosis: Imagining the Unimaginable

Cystic fibrosis is the most common life-shortening genetic disease affecting Caucasians, clinically manifested by fat malabsorption, poor growth and nutrition, and recurrent sinopulmonary infections. Newborn screening programs for cystic fibrosis are now implemented throughout the United States and in many nations worldwide. Early diagnosis and interventions have led to improved clinical outcomes for people with cystic fibrosis. Newer cystic fibrosis transmembrane conductance regulator potentiators and correctors with mutation-specific effects have increasingly been used in children, and these agents are revolutionizing care. Indeed, it is possible that highly effective modulator therapy used early in life could profoundly affect the trajectory of cystic fibrosis lung disease, and primary prevention may be achievable.

Translating Molecular Technologies into Routine Newborn Screening Practice

As biotechnologies advance and better treatment regimens emerge, there is a trend toward applying more advanced technologies and adding more conditions to the newborn screening (NBS) panel. In the current Recommended Uniform Screening Panel (RUSP), all conditions but one, congenital hypothyroidism, have well-defined genes and inheritance patterns, so it is beneficial to incorporate molecular testing in NBS when it is necessary and appropriate. Indeed, the applications of molecular technologies have taken NBS to previously uncharted territory. In this paper, based on our own program experience and what has been reported in the literature, we describe current practices regarding the applications of molecular technologies in routine NBS practice in the era of genomic and precision medicine.

Targeted next generation sequencing for newborn screening of Menkes disease

PURPOSE

Population-based newborn screening (NBS) allows early detection and treatment of inherited disorders. For certain medically-actionable conditions, however, NBS is limited by the absence of reliable biochemical signatures amenable to detection by current platforms. We sought to assess the analytic validity of an ATP7A targeted next generation DNA sequencing assay as a potential newborn screen for one such disorder, Menkes disease.

METHODS

Dried blood spots from control or Menkes disease subjects (n = 22) were blindly analyzed for pathogenic variants in the copper transport gene, ATP7A. The analytical method was optimized to minimize cost and provide rapid turnaround time.

RESULTS

The algorithm correctly identified pathogenic ATP7A variants, including missense, nonsense, small insertions/deletions, and large copy number variants, in 21/22 (95.5%) of subjects, one of whom had inconclusive diagnostic sequencing previously. For one false negative that also had not been detected by commercial molecular laboratories, we identified a deep intronic variant that impaired ATP7A mRNA splicing.

CONCLUSIONS

Our results support proof-of-concept that primary DNA-based NBS would accurately detect Menkes disease, a disorder that fulfills Wilson and Jungner screening criteria and for which biochemical NBS is unavailable. Targeted next generation sequencing for NBS would enable improved Menkes disease clinical outcomes, establish a platform for early identification of other unscreened disorders, and complement current NBS by providing immediate data for molecular confirmation of numerous biochemically screened condition.

Performance of a Three-Tier (IRT-DNA-IRT) Cystic Fibrosis Screening Algorithm in British Columbia

Newborn screening for Cystic Fibrosis has been implemented in most programs worldwide, but the approach used varies, including combinations of immunoreactive trypsinogen (IRT) and CFTR mutation analysis on one or more specimens. The British Columbia (BC) newborn screening program tests ~45,000 infants per year in BC and the Yukon Territory, covering almost 1.5 million km2 in western Canada. CF screening was initiated using an IRT-DNA-IRT approach with a second bloodspot card at 21 days of age for all CFTR mutation heterozygotes and any non-carriers in the top 0.1% for IRT. This second IRT was implemented to avoid sweat testing of infants without persistent hypertrypsinemia, reducing the burden of travel for families. Over nine years (2010-2018), 401,977 infants were screened and CF was confirmed in 76, and a further 28 were deemed CF screen positive inconclusive diagnosis (CFSPID). Day 21 IRT was normal in 880 CFTR mutation carriers who were quoted a very low CF risk and offered optional sweat testing. Only 13% of families opted for sweat testing and a total of 1036 sweat tests were avoided. There were six false negative CF cases (and three CFSPID) due to a low initial IRT or no CFTR mutations. Although one CFSPID case had a normal repeat IRT result, the addition of the day 21 IRT did not contribute to any CF false negatives.

The Role of Extended CFTR Gene Sequencing in Newborn Screening for Cystic Fibrosis

There has been considerable progress in the implementation of newborn screening (NBS) programs for cystic fibrosis (CF), with DNA analysis being part of an increasing number of strategies. Thanks to advances in genomic sequencing technologies, CFTR-extended genetic analysis (EGA) by sequencing its coding regions has become affordable and has already been included as part of a limited number of core NBS programs, to the benefit of admixed populations. Based on results analysis of existing programs, the values and challenges of EGA are reviewed in the perspective of its implementation on a larger scale. Sensitivity would be increased at best by using EGA as a second tier, but this could be at the expense of positive predictive value, which improves, however, if EGA is applied after testing a variant panel. The increased detection of babies with an inconclusive diagnosis has proved to be a major drawback in programs using EGA. The lack of knowledge on pathogenicity and penetrance associated with numerous variants hinders the introduction of EGA as a second tier, but EGA with filtering for all known CF variants with full penetrance could be a solution. The issue of incomplete knowledge is a real challenge in terms of the implemention of NBS extended to many genetic diseases.

Metabolomics to Improve the Diagnostic Efficiency of Inborn Errors of Metabolism

Early diagnosis of inborn errors of metabolism (IEM)—a large group of congenital disorders—is critical, given that many respond well to targeted therapy. Newborn screening programs successfully capture a proportion of patients enabling early recognition and prompt initiation of therapy. For others, the heterogeneity in clinical presentation often confuses diagnosis with more common conditions. In the absence of family history and following clinical suspicion, the laboratory diagnosis typically begins with broad screening tests to circumscribe specialised metabolite and/or enzyme assays to identify the specific IEM. Confirmation of the biochemical diagnosis is usually achieved by identifying pathogenic genetic variants that will also enable cascade testing for family members. Unsurprisingly, this diagnostic trajectory is too often a protracted and lengthy process resulting in delays in diagnosis and, importantly, therapeutic intervention for these rare conditions is also postponed. Implementation of mass spectrometry technologies coupled with the expanding field of metabolomics is changing the landscape of diagnosing IEM as numerous metabolites, as well as enzymes, can now be measured collectively on a single mass spectrometry-based platform. As the biochemical consequences of impaired metabolism continue to be elucidated, the measurement of secondary metabolites common across groups of IEM will facilitate algorithms to further increase the efficiency of diagnosis.

Evaluating sequence data quality from the Swift Accel-Amplicon CFTR Panel

Cystic fibrosis (CF) is one of the most common genetic diseases worldwide with high carrier frequencies across different ethnicities. Next generation sequencing of the cystic fibrosis transmembrane conductance regulator (CFTR) gene has proven to be an effective screening tool to determine carrier status with high detection rates. Here, we evaluate the performance of the Swift Biosciences Accel-Amplicon CFTR Capture Panel using CFTR-positive DNA samples. This assay is a one-day protocol that allows for one-tube reaction of 87 amplicons that span all coding regions, 5' and 3'UTR, as well as four intronic regions. In this study, we provide the FASTQ, BAM, and VCF files on seven unique CFTR-positive samples and one normal control sample (14 samples processed including repeated samples). This method generated sequencing data with high coverage and near 100% on-target reads. We found that coverage depth was correlated with the GC content of each exon. This dataset is instrumental for clinical laboratories that are evaluating this technology as part of their carrier screening program.

A brief history of human disease genetics

A primary goal of human genetics is to identify DNA sequence variants that influence biomedical traits, particularly those related to the onset and progression of human disease. Over the past 25 years, progress in realizing this objective has been transformed by advances in technology, foundational genomic resources and analytical tools, and by access to vast amounts of genotype and phenotype data. Genetic discoveries have substantially improved our understanding of the mechanisms responsible for many rare and common diseases and driven development of novel preventative and therapeutic strategies. Medical innovation will increasingly focus on delivering care tailored to individual patterns of genetic predisposition.

What Genomic Sequencing Can Offer Universal Newborn Screening Programs

Massively parallel sequencing, also known as next-generation sequencing, has the potential to significantly improve newborn screening programs in the United States and around the world. Compared to genetic tests whose use is well established, sequencing allows for the analysis of large amounts of DNA, providing more comprehensive and rapid results at a lower cost. It is already being used in limited ways by some public health newborn screening laboratories in the United States and other countries-and it is under study for broader and more widespread use, including as a core part of newborn screening programs. Sequencing technology has the potential to significantly improve these essential public health programs. For many of the conditions that newborns are already screened for, sequencing can return more specific and more sensitive results. The technology could also enable newborn screening programs to expand the list of rare pediatric conditions that they look for, thereby identifying more infants who can benefit from immediate care.

Single-Gene Sequencing in Newborn Screening: Success, Challenge, Hope

Some state-based newborn screening programs in the United States already use sequencing technology, as a secondary screening test for individual conditions rather than as a broad screening tool. Newborn screening programs sequence an individual gene, such as the cystic fibrosis transmembrane conductance regulator, which causes cystic fibrosis, after an initial biochemical test suggests that a baby might have a condition related to that gene. The experiences of state public health departments with individual-gene sequencing illustrate both the usefulness of the technology and its complexities. Here I discuss how newborn screening programs investigate cystic fibrosis and, as another example, adrenoleukodystrophy through individual gene sequencing.

Combining newborn metabolic and DNA analysis for second-tier testing of methylmalonic acidemia

Purpose

Improved second-tier tools are needed to reduce false-positive outcomes in newborn screening (NBS) for inborn metabolic disorders on the Recommended Universal Screening Panel (RUSP).

Methods

We designed an assay for multiplex sequencing of 72 metabolic genes (RUSPseq) from newborn dried blood spots. Analytical and clinical performance was evaluated in 60 screen-positive newborns for methylmalonic acidemia (MMA) reported by the California Department of Public Health NBS program. Additionally, we trained a Random Forest machine learning classifier on NBS data to improve prediction of true and false-positive MMA cases.

Results

Of 28 MMA patients sequenced, we found two pathogenic or likely pathogenic (P/LP) variants in a MMA-related gene in 24 patients, and one pathogenic variant and a variant of unknown significance (VUS) in 1 patient. No such variant combinations were detected in MMA false positives and healthy controls. Random Forest–based analysis of the entire NBS metabolic profile correctly identified the MMA patients and reduced MMA false-positive cases by 51%. MMA screen-positive newborns were more likely of Hispanic ethnicity.

Conclusion

Our two-pronged approach reduced false positives by half and provided a reportable molecular finding for 89% of MMA patients. Challenges remain in newborn metabolic screening and DNA variant interpretation in diverse multiethnic populations.

Advances in the Diagnosis and Management of Cystic Fibrosis in the Genomic Era

BACKGROUND

Cystic fibrosis (CF) is a complex autosomal recessive disease that continues to present unique diagnostic challenges. Because CF was first described in 1938, there has been a substantial growth of genetic and phenotypic information about the disorder. During the past few years, as more evidence has become available, a consortium of international experts determined that the 2008 guidelines from the CF Foundation needed to be reviewed and updated.

CONTENT

The goal of this review is to highlight the latest advances in CF multidisciplinary care, together with the recent updates to the 2017 CF Foundation diagnostic guidelines.

SUMMARY

Data from newborn screening programs, patient registries, clinical databases, and functional research have led to a better understanding of the CF transmembrane conductance regulator (CFTR) gene. Recent consensus guidelines have provided recommendations for clinicians and laboratorians to better assist with interpretation of disease status and related CF mutations. The highly recommended Clinical and Functional Translation of CFTR project should be the first resource in the evaluation of disease severity for CF mutations. Screen-positive newborns and patients with high clinical suspicion for CF are always recommended to undergo confirmatory sweat chloride testing with interpretations based on updated reference intervals. Every patient diagnosed with CF should receive genotyping, as novel molecular therapies are becoming standard of practice. The future of CF management must consider healthcare system disparities as CF transitions from a historically childhood disease to a predominantly adult epidemic.