Neonatal screening for Duchenne/Becker muscular dystrophy; Reconsideration based on molecular diagnosis and potential therapeutics

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.

Myoblast Transplantation: What's Going on?

Muscle tissue, due to its syncytial cellular structure and specific nerve and vascular requirements, cannot be transplanted as an organ. In an effort to use transplantation to overcome genetically determined biochemical deficiencies in muscle, attention has focused on delivering the developmental precursors of mature muscle fibers, myoblasts, as donor cells for cellular transplantation. Consequent to a brief report showing limited success of the technique in mice in 1988, human trials were summarily designed, funded, and initiated. The human trials have spurred more controversy than concrete data, with more reports appearing in the popular press than in scientific journals. This review summarizes the events leading to the current state of affairs, and underscores the biological hurdles facing myoblast transplantation before it can be considered a therapeutic modality.

Twenty-year follow-up of newborn screening for patients with muscular dystrophy

INTRODUCTION

An opt-out newborn screening (NBS) program for Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) was implemented at 2 hospitals in Pittsburgh, Pennsylvania, between 1987 and 1995.

METHODS

For patients and their parents in families who received a diagnosis of DMD or BMD, either by NBS or by traditional diagnostics after symptom onset, attitudes toward NBS for DMD and BMD were assessed.

RESULTS

All patients and most parents supported NBS for DMD and BMD. In contrast to the NBS parent cohort, the non-NBS cohort felt that diagnosis by NBS would cause anxiety.

CONCLUSIONS

There was strong support of NBS for DMD and BMD in both patients and their parents in families who received a diagnosis through NBS or through traditional diagnostics. No negative psychosocial impacts of NBS were identified among those families who received a diagnosis through NBS.

Development of DNA confirmatory and high-risk diagnostic testing for newborns using targeted next-generation DNA sequencing

PURPOSE

Genetic testing is routinely used for second-tier confirmation of newborn sequencing results to rule out false positives and to confirm diagnoses in newborns undergoing inpatient and outpatient care. We developed a targeted next-generation sequencing panel coupled with a variant processing pipeline and demonstrated utility and performance benchmarks across multiple newborn disease presentations in a retrospective clinical study.

METHODS

The test utilizes an in silico gene filter that focuses directly on 126 genes related to newborn screening diseases and is applied to the exome or a next-generation sequencing panel called NBDx. NBDx targets the 126 genes and additional newborn-specific disorders. It integrates DNA isolation from minimally invasive biological specimens, targeted next-generation screening, and rapid characterization of genetic variation.

RESULTS

We report a rapid parallel processing of 8 to 20 cases within 105 hours with high coverage on our NBDx panel. Analytical sensitivity of 99.8% was observed across known mutation hotspots. Concordance calls with or without clinical summaries were 94% and 75%, respectively.

CONCLUSION

Rapid, automated targeted next-generation sequencing and analysis are practical in newborns for second-tier confirmation and neonatal intensive care unit diagnoses, laying a foundation for future primary DNA-based molecular screening of additional disorders and improving existing molecular testing options for newborns.

Parental attitudes toward newborn screening for Duchenne/Becker muscular dystrophy and spinal muscular atrophy

INTRODUCTION

Disease inclusion in the newborn screening (NBS) panel should consider the opinions of those most affected by the outcome of screening. We assessed the level and factors that affect parent attitudes regarding NBS panel inclusion of Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and spinal muscular atrophy (SMA).

METHODS

The attitudes toward NBS for DMD, BMD, and SMA were surveyed and compared for 2 categories of parents, those with children affected with DMD, BMD, or SMA and expectant parents unselected for known family medical history.

RESULTS

The level of support for NBS for DMD, BMD, and SMA was 95.9% among parents of children with DMD, BMD, or SMA and 92.6% among expectant parents.

CONCLUSIONS

There was strong support for NBS for DMD, BMD, and SMA in both groups of parents. Given advances in diagnostics and promising therapeutic approaches, discussion of inclusion in NBS should continue.

Screening for conditions that do not meet the Wilson and Jungner criteria: the case of Duchenne muscular dystrophy

In this manuscript, I examine four overlapping policy and ethical issues regarding screening newborns (and infants) for Duchenne muscular dystrophy (DMD). First, what are the risks and benefits of expanding newborn screening (NBS) to include DMD? Second, if NBS were to expand to include DMD, should it require informed consent? Third, should NBS for DMD be limited to boys? Why or why not? Fourth, when is the ideal timing for screening (prenatal, newborn, or later in infancy) and what factors influence this determination? I argue that decisions about when, how, and whom to test reflect a tension between maximizing uptake and diagnosis versus maximizing autonomy and choice with respect to genetic information. I conclude that screening for DMD is a valid moral option, but not as part of the mandatory NBS population program. Rather, I propose that screening for DMD should be offered only on a voluntary basis beyond the newborn period. I support offering this screening to families of young boys and girls to ensure that all children and their families can benefit from early diagnosis and its reproductive implications. A rigorous consent process will be necessary to ensure that the decision whether or not to test is a voluntary and informed choice.

Neonatal screening for Duchenne muscular dystrophy: a novel semiquantitative application of the bioluminescence test for creatine kinase in a pilot national program in Cyprus

The objectives of this study were to evaluate a novel semiquantitative application of the bioluminescence test for screening newborns for Duchenne muscular dystrophy (DMD) and to use this technique in a pilot national program. The study was performed on the island of Cyprus, which provides ideal conditions for maximizing the prevention rate due to the small size of the country, the well-defined population, and the high degree of awareness of the public concerning genetic diseases. Guthrie spots were obtained through the national screening center for phenylketonuria and congenital hypothyroidism. The bioluminescence method for measuring creatine kinase (CK) in dried blood spots was adapted for use in a semiquantitative way. During the first 6 years of the program (1992-1997), we screened 30,014 samples and found 43 with initially high CK values. We were able to obtain repeat specimens in 35 cases. Of the repeat samples, 30 were found to have normal activity, giving a false-positive rate of 0.10%. Five boys had persistent CK elevations and were confirmed to be DMD or Becker (BMD) cases by DNA analysis and/or dystrophin analysis. The semiquantitative application of the bioluminescence assay of CK that we have introduced has proved to be a fast and reliable method for screening large numbers of samples for DMD. It has a low rate of false positives, which compares favorably with that of other DMD screening programs. Although it is early to evaluate its impact fully, the program seems to be bringing about the anticipated benefits to affected families.