Two years of newborn screening for Duchenne muscular dystrophy as a part of the statewide Early Check research program in North Carolina.

PURPOSE: Current and emerging treatments for Duchenne muscular dystrophy (DMD) position DMD as a candidate condition for newborn screening (NBS). In anticipation of the nomination of DMD for universal NBS, we conducted a prospective study under the Early Check voluntary NBS research program in North Carolina, United States. METHODS: We performed screening for creatine kinase-MM (CK-MM), a biomarker of muscle damage, on residual routine newborn dried blood spots (DBS) from participating newborns. Total creatine kinase testing and next generation sequencing of an 86-neuromuscular gene panel that included DMD were offered to parents of newborns who screened positive. Bivariate and multivariable analyses were performed to assess effects of biological and demographic predictors on CK-MM levels in DBS. RESULTS: We screened 13,354 newborns and identified 2 males with DMD. The provisional 1626 ng/mL cutoff was raised to 2032 ng/mL to improve specificity, and additional cutoffs (900 and 360 ng/mL) were implemented to improve sensitivity for older and low-birthweight newborns. CONCLUSION: Population-scale screening for elevated CK-MM in DBS is a feasible approach to identify newborns with DMD. Inclusion of birthweight- and age-specific cutoffs, repeat creatine kinase testing after 72 hours of age, and DMD sequencing improve sensitivity and specificity of screening.

Evaluation of the GSP Creatine Kinase-MM Assay and Assessment of CK-MM Stability in Newborn, Patient, and Contrived Dried Blood Spots for Newborn Screening for Duchenne Muscular Dystrophy.

Duchenne Muscular Dystrophy (DMD) is a fatal X-linked disorder with a birth prevalence of 19.8:100,000 males worldwide. Elevated concentration of the muscle enzyme creatine kinase-MM (CK-MM) allows for presymptomatic screening of newborns using Dried Blood Spots (DBS). We evaluated imprecision and carryover of the FDA-approved PerkinElmer GSP Neonatal CK-MM kit over multiple runs, days, and operators, followed by quantification of CK-MM loss in stored newborn, contrived, and non-newborn patient DBS resulting from exposure to ambient versus low humidity (50-day trial), and high humidity and high temperature (8-day trial). Imprecision %CV was ≤14% for all verification comparisons and over 6 months of testing. On average, the mean CK-MM recovery after 50 days was >80% of initial concentration for all sample types stored in low humidity and <80% in ambient humidity. After 8 days of storage in high humidity and high temperature, the mean recovery for newborn samples was <80%. Verification results for the GSP Neonatal CK-MM assay were concordant with kit parameters and the assay performed consistently over 6 months. CK-MM degradation in ambient storage can be mitigated by reducing exposure to humidity. Assessment of DBS shipping and storage conditions is recommended prior to implementing DMD screening.

A Voluntary Statewide Newborn Screening Pilot for Spinal Muscular Atrophy: Results from Early Check.

Prior to statewide newborn screening (NBS) for spinal muscular atrophy (SMA) in North Carolina, U.S.A., we offered voluntary screening through the Early Check (EC) research study. Here, we describe the EC experience from October 2018 through December 2020. We enrolled a total of 12,065 newborns and identified one newborn with 0 copies of SMN1 and two copies of SMN2, consistent with severe early onset of SMA. We also detected one false positive result, likely stemming from an unrelated blood disorder associated with a low white blood cell count. We evaluated the timing of NBS for babies enrolled prenatally (n = 932) and postnatally (n = 11,133) and reasons for delays in screening and reporting. Although prenatal enrollment led to faster return of results (median = 13 days after birth), results for babies enrolled postnatally were still available within a timeframe (median = 21 days after birth) that allowed the opportunity to receive essential treatment early in life. We evaluated an SMA q-PCR screening method at two separate time points, confirming the robustness of the assay. The pilot project provided important information about SMA screening in anticipation of forthcoming statewide expansion as part of regular NBS.