Newborn screening for Duchenne muscular dystrophy

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.

Risk of Obstructive Sleep Apnea in Saudi Male Boys with Duchenne Muscular Dystrophy (DMD)

Background

Duchenne muscular dystrophy (DMD) patients are at a high risk of developing sleep-related breathing disorders (SRBD) such as obstructive sleep apnea (OSA). This study aimed to determine the risk of developing OSA among DMD patients.

Methods

This cross-sectional study was conducted from February 2022 to July 2022 in a tertiary healthcare facility. As a screening tool for OSA, we used the Pediatric Sleep Questionnaire (PSQ).

Results

Subjects included 60 boys with DMD, mean age 10.15 ± 3.54 years. The mean BMI for all subjects was 18.9 ± 4.08 kg/m2. Of these, 22 (36.7%) children were at high risk of OSA. Children who were overweight, and on steroids tended to be at higher risk of developing OSA (P < 0.043) and (P < 0.029) respectively.

Conclusion

Our study shows a significant risk of OSA in DMD patients. Therefore, Sleep studies should be part of the standard of care for DMD patients.

Coexistence of a Heterozygous Caveolin-3 Deletion and a Novel Dystrophin Gene Mutation in a Duchenne Muscular Dystrophy Patient

Inherited muscular abnormalities are debilitating disorders that greatly diminish the quality of life in affected individuals. Mutations in proteins such as dystrophin and caveolin, which together with other proteins form structural connections between the cytoskeleton and the extracellular matrix, are frequently the culprit of muscular dystrophies. In this case report, we describe a patient with a novel pathogenic dystrophin mutation co-existing with a caveolin-3 deletion. While genetically composed of this unique combination, the patient phenotypically presented with a primary clinical manifestation of Duchenne muscular dystrophy (DMD) in contrast to other cases of dual mutations in dystrophin and dystrophin-associated proteins.

Newborn Screening for Duchenne Muscular Dystrophy: First Year Results of a Population-Based Pilot

Advancements in therapies for Duchenne muscular dystrophy (DMD) have made diagnosis within the newborn period a high priority. We undertook a consortia approach to advance DMD newborn screening in the United States. This manuscript describes the formation of the Duchenne Newborn Screening Consortium, the development of the pilot protocols, data collection tools including parent surveys, and findings from the first year of a two-year pilot. The DMD pilot design is population-based recruitment of infants born in New York State. Data tools were developed to document the analytical and clinical validity of DMD NBS, capture parental attitudes, and collect longitudinal health information for diagnosed newborns. Data visualizations were updated monthly to inform the consortium on enrollment. After 12 months, 15,754 newborns were screened for DMD by the New York State Newborn Screening (NYS NBS) Program. One hundred and forty screened infants had borderline screening results, and sixteen infants were referred for molecular testing. Three male infants were diagnosed with dystrophinopathy. Data from the first year of a two-year NBS pilot for DMD demonstrate the feasibility of NBS for DMD. The consortia approach was found to be a useful model, and the Newborn Screening Translational Research Network's data tools played a key role in describing the NBS pilot findings and engaging stakeholders.

Use of EP3533-Enhanced Magnetic Resonance Imaging as a Measure of Disease Progression in Skeletal Muscle of mdx Mice

As putative treatments are developed for Duchenne muscular dystrophy (DMD), sensitive, non-invasive measures are increasingly important to quantify disease progression. Fibrosis is one of the histological hallmarks of muscular dystrophy and has been directly linked to prognosis. EP3533 is a novel contrast agent with an affinity to collagen 1 that has demonstrated a significant and high correlation to ex vivo fibrosis quantification. Halofuginone is an established anti-fibrotic compound shown to reduce collagen skeletal muscle fibrosis in murine models of DMD. This experiment explored whether EP3533 could be used to detect signal change in skeletal muscle of mdx mice before and after a 12 week course of halofuginone compared to controls. Four age-matched groups of treated and untreated mice were evaluated: 2 groups of mdx (n = 8 and n = 13, respectively), and 2 groups of BL10 mice (n = 5 and n = 3, respectively). Treated mice received an intraperitoneal injection with halofuginone three times per week for 12 weeks, with the remaining mice being given vehicle. Both mdx groups and the untreated BL10 were scanned at baseline, then all groups were scanned on week 13. All subjects were scanned using a 7T Varian scanner before and after administration of EP3533 using a T1 mapping technique. Mice underwent grip testing in week 13 prior to dissection. Skeletal muscle was used for Masson's trichrome quantification, hydroxyproline assay, and immunofluorescent antibody staining. Untreated mdx mice demonstrated a significant increase in R1 signal from pre- to post-treatment scan in three out of four muscles (gastrocnemius p = 0.04, hamstrings p = 0.009, and tibialis anterior p = 0.01), which was not seen in either the treated mdx or the BL10 groups. Histological quantification of fibrosis also demonstrated significantly higher levels in the untreated mdx mice with significant correlation seen between histology and EP3533 signal change. Forelimb weight adjusted-grip strength was significantly lower in the untreated mdx group, compared to the treated group. EP3533 can be used over time as an outcome measure to quantify treatment effect of an established anti-fibrotic drug. Further studies are needed to evaluate the use of this contrast agent in humans.

Duchenne Muscular Dystrophy Newborn Screening: Evaluation of a New GSP® Neonatal Creatine Kinase-MM Kit in a US and Danish Population

Duchenne muscular dystrophy (DMD/Duchenne) is a progressive X-linked disease and is the most common pediatric-onset form of muscular dystrophy, affecting approximately 1:5000 live male births. DNA testing for mutations in the dystrophin gene confirms the diagnosis of this disorder. This study involves assessment of screening newborns for DMD using an immunoassay for muscle-type (MM) creatine kinase (CK) isoform-the GSP Neonatal CK-MM kit. Comparisons were made with CK activity determination by fluorescence measurement. In addition, the study evaluated the effect of gestational age, age of infant at time of sampling and how stable the CK-MM was over time. This assay discriminates well between normal, unaffected and Duchenne affected populations and is suitable for Duchenne newborn screening.

Noninvasive quantification of fibrosis in skeletal and cardiac muscle in mdx mice using EP3533 enhanced magnetic resonance imaging

PURPOSE

Duchenne muscular dystrophy (DMD) is a genetic condition caused by mutations in the DMD gene leading to muscle degeneration, fatty replacement of muscle cells and fibrosis. A major obstacle to advancing therapeutic research into muscular dystrophies is development of sensitive, noninvasive outcome measures. To date, no validated method to noninvasively quantify fibrosis within skeletal muscle exists. EP3533 is a gadolinium-based MRI contrast agent with an affinity to collagen-1. The purpose of this study was to determine whether EP3533-enhanced MRI could quantify fibrosis in a murine model of DMD (mdx) in muscle.

METHODS

Mdx (n = 8) and control mice (BL10; n = 5) underwent contrast-enhanced MRI acquisitions with EP3533. T₁ mapping pre- and postcontrast was performed in skeletal and cardiac muscle. Post-MRI the tibialis anterior (TA) and gastrocnemius (GCN) muscles and the heart were removed for fibrosis quantification by means of Masson's trichrome staining and the hydroxyproline assay.

RESULTS

Significant differences in postcontrast R₁ were demonstrated between mdx and BL10 mice using EP3533 (cardiac P = 0.02, GCN P = 0.04, TA P = 0.04). Change in R₁ from baseline following EP3533 administration correlated strongly to hydroxyproline levels (GCN: r = 0.83, P = 0.001; TA: r = 0.73, P = 0.01).

CONCLUSIONS

This study provides evidence for the suitability of EP3533 in the quantification of muscular fibrosis in mdx mice and demonstrated that EP3533-derived measurements correlated strongly to ex vivo fibrosis measurement.

Aquatic therapy for children with Duchenne muscular dystrophy: a pilot feasibility randomised controlled trial and mixed-methods process evaluation

BACKGROUND

Duchenne muscular dystrophy (DMD) is a rare disease that causes the progressive loss of motor abilities such as walking. Standard treatment includes physiotherapy. No trial has evaluated whether or not adding aquatic therapy (AT) to land-based therapy (LBT) exercises helps to keep muscles strong and children independent.

OBJECTIVES

To assess the feasibility of recruiting boys with DMD to a randomised trial evaluating AT (primary objective) and to collect data from them; to assess how, and how well, the intervention and trial procedures work.

DESIGN

Parallel-group, single-blind, randomised pilot trial with nested qualitative research.

SETTING

Six paediatric neuromuscular units.

PARTICIPANTS

Children with DMD aged 7-16 years, established on corticosteroids, with a North Star Ambulatory Assessment (NSAA) score of 8-34 and able to complete a 10-m walk without aids/assistance. Exclusions: > 20% variation between baseline screens 4 weeks apart and contraindications.

INTERVENTIONS

Participants were allocated on a 1 : 1 ratio to (1) optimised, manualised LBT (prescribed by specialist neuromuscular physiotherapists) or (2) the same plus manualised AT (30 minutes, twice weekly for 6 months: active assisted and/or passive stretching regime; simulated or real functional activities; submaximal exercise). Semistructured interviews with participants, parents (n = 8) and professionals (n = 8) were analysed using Framework analysis. An independent rater reviewed patient records to determine the extent to which treatment was optimised. A cost-impact analysis was performed. Quantitative and qualitative data were mixed using a triangulation exercise.

MAIN OUTCOME MEASURES

Feasibility of recruiting 40 participants in 6 months, participant and therapist views on the acceptability of the intervention and research protocols, clinical outcomes including NSAA, independent assessment of treatment optimisation and intervention costs.

RESULTS

Over 6 months, 348 children were screened - most lived too far from centres or were enrolled in other trials. Twelve (30% of target) were randomised to AT (n = 8) or control (n = 4). People in the AT (n = 8) and control (n = 2: attrition because of parental report) arms contributed outcome data. The mean change in NSAA score at 6 months was -5.5 [standard deviation (SD) 7.8] for LBT and -2.8 (SD 4.1) in the AT arm. One boy suffered pain and fatigue after AT, which resolved the same day. Physiotherapists and parents valued AT and believed that it should be delivered in community settings. The independent rater considered AT optimised for three out of eight children, with other children given programmes that were too extensive and insufficiently focused. The estimated NHS costs of 6-month service were between £1970 and £2734 per patient.

LIMITATIONS

The focus on delivery in hospitals limits generalisability.

CONCLUSIONS

Neither a full-scale frequentist randomised controlled trial (RCT) recruiting in the UK alone nor a twice-weekly open-ended AT course delivered at tertiary centres is feasible. Further intervention development research is needed to identify how community-based pools can be accessed, and how families can link with each other and community physiotherapists to access tailored AT programmes guided by highly specialised physiotherapists. Bayesian RCTs may be feasible; otherwise, time series designs are recommended.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN41002956.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 27. See the NIHR Journals Library website for further project information.

Echocardiographic Image Quality Deteriorates with Age in Children and Young Adults with Duchenne Muscular Dystrophy

BACKGROUND

Advances in medical care for patients with Duchenne muscular dystrophy (DMD) have resulted in improved survival and an increased prevalence of cardiomyopathy. Serial echocardiographic surveillance is recommended to detect early cardiac dysfunction and initiate medical therapy. Clinical anecdote suggests that echocardiographic quality diminishes over time, impeding accurate assessment of left ventricular systolic function. Furthermore, evidence-based guidelines for the use of cardiac imaging in DMD, including cardiac magnetic resonance imaging (CMR), are limited. The objective of our single-center, retrospective study was to quantify the deterioration in echocardiographic image quality with increasing patient age and identify an age at which CMR should be considered.

METHODS

We retrospectively reviewed and graded the image quality of serial echocardiograms obtained in young patients with DMD. The quality of 16 left ventricular segments in two echocardiographic views was visually graded using a binary scoring system. An endocardial border delineation percentage (EBDP) score was calculated by dividing the number of segments with adequate endocardial delineation in each imaging window by the total number of segments present in that window and multiplying by 100. Linear regression analysis was performed to model the relationship between the EBDP scores and patient age.

RESULTS

Fifty-five echocardiograms from 13 patients (mean age 11.6 years, range 3.6-19.9) were systematically reviewed. By 13 years of age, 50% of the echocardiograms were classified as suboptimal with ≥30% of segments inadequately visualized, and by 15 years of age, 78% of studies were suboptimal. Linear regression analysis revealed a negative correlation between patient age and EBDP score (r = -2.49, 95% confidence intervals -4.73, -0.25; p = 0.032), with the score decreasing by 2.5% for each 1 year increase in age.

CONCLUSION

Echocardiographic image quality declines with increasing age in DMD. Alternate imaging modalities may play a role in cases of poor echocardiographic image quality.

Increased collagen cross-linking is a signature of dystrophin-deficient muscle

Introduction

Collagen cross‐linking is a key parameter in extracellular matrix (ECM) maturation, turnover, and stiffness. We examined aspects of collagen cross‐linking in dystrophin‐deficient murine, canine, and human skeletal muscle.

Methods

DMD patient biopsies and samples from mdx mice and golden retriever muscular dystrophy dog samples (with appropriate controls) were analyzed. Collagen cross‐linking was evaluated using solubility and hydroxyproline assays. Expression of the cross‐linking enzyme lysyl oxidase (LOX) was determined by real‐time polymerase chain reaction, immunoblotting, and immunofluorescence.

Results

LOX protein levels are increased in dystrophic muscle from all species evaluated. Dystrophic mice and dogs had significantly higher cross‐linked collagen than controls, especially in the diaphragm. Distribution of intramuscular LOX was heterogeneous in all samples, but it increased in frequency and intensity in dystrophic muscle.

Conclusion

These findings implicate elevated collagen cross‐linking as an important component of the disrupted ECM in dystrophic muscles, and heightened cross‐linking is evident in mouse, dog, and man. Muscle Nerve54: 71–78, 2016

Treatable renal failure found in non-ambulatory Duchenne muscular dystrophy patients

Duchenne muscular dystrophy (DMD) is a progressive muscular disorder in which respiratory and heart failures are the main causes of death. Intensive intervention in respiratory and cardiac function has dramatically improved the prognosis; however, dysfunction in other multiple organs may emerge in the later stages of the disease. We report the case of four non-ambulatory DMD patients who presented with renal failure. Common findings included decreased fluid intake, use of diuretics, and presence of chronic heart failure. The levels of serum cystatin C (CysC), a marker of kidney function unaffected by reduced muscle mass, were elevated in all four patients. In two patients, renal failure improved by increasing fluid intake, and discontinuing or reducing the dose of diuretics. The findings suggest that non-ambulatory DMD patients are at a risk of reduced kidney perfusion, which potentially leads to prerenal failure. Therefore, in DMD patients, dehydration signs and CysC levels should be monitored.

Muscular dystrophy-related hospitalizations among male pediatric patients in the United States

OBJECTIVE

While the economic burden of muscular dystrophy (MD) has been well documented, little is known of specific costs associated with Duchenne muscular dystrophy (DMD), the most prevalent form of MD. This study assessed trends in MD-related hospitalizations and costs among young males, which may reflect utilization of the DMD population in the United States.

STUDY DESIGN

A retrospective observational study of hospitalizations of males aged 0-20 years with a primary diagnosis code for MD was conducted using data from a weighted, nationally representative database of pediatric hospitalizations in the US. Rates, characteristics and cost of MD-related hospitalizations were compared to hospitalizations not related to MD.

RESULTS

The rate of MD-related hospitalizations increased by 9% between 2000 and 2006 and then decreased by 13% in 2009. The mean length of stay for discharges related to MD was approximately 9 days during each study year. The most frequent observed diagnoses (other than MD) and procedures were for respiratory-related complications. The mean total costs for MD-related discharges increased across the study period from $26,785 in 2000 to $42,751 in 2009.

CONCLUSION

This study provides baseline and trend data describing hospitalizations of male pediatric patients with MD that may be used as baseline measurements for assessment of the impact of new strategies for managing the disease. Further assessment of the burden and the clinical, economic, and humanistic impacts of DMD is warranted.

Haplotype-based approach for noninvasive prenatal tests of Duchenne muscular dystrophy using cell-free fetal DNA in maternal plasma

PURPOSE

This study demonstrates noninvasive prenatal testing (NIPT) for Duchenne muscular dystrophy (DMD) using a newly developed haplotype-based approach.

METHODS

Eight families at risk for DMD were recruited for this study. Parental haplotypes were constructed using target-region sequencing data from the parents and the probands. Fetal haplotypes were constructed using a hidden Markov model through maternal plasma DNA sequencing. The presence of haplotypes linked to the maternal mutant alleles in males indicated affected fetuses. This method was further validated by comparing the inferred single-nucleotide polymorphism (SNP) genotypes to the direct sequencing results of fetal genomic DNA. Prenatal diagnosis was confirmed with amniocentesis, and those results were interpreted in a blinded fashion.

RESULTS

The results showed an average accuracy of 99.98% for the total inferred maternal SNPs. With a mean depth of 30× achieved in the 10-Mb target region of each sample, the noninvasive results were consistent with those of the invasive procedure.

CONCLUSION

This is the first report of NIPT for DMD and the first application of a haplotype-based approach in NIPT for X-linked diseases. With further improvements in accuracy, this haplotype-based strategy could be feasible for NIPT for DMD and even other X-linked single-gene disorders.

Newborn bloodspot screening for Duchenne muscular dystrophy: 21 years experience in Wales (UK)

Duchenne muscular dystrophy (DMD), a progressive X-linked neuromuscular disorder, has an estimated worldwide incidence of 1:3500 male births. Currently, there are no curative treatments and the mean age of diagnosis is 5 years. In addition, subsequent pregnancies frequently occur before a diagnosis is made in an index case. An 'opt in' screening programme was introduced in Wales in 1990 with the aim to: reduce the diagnostic delay, permit reproductive choice and allow planning of the care of the affected boy. Newborn bloodspots were collected routinely as part of the Wales newborn screening programme. Specific consent was obtained for this test separately from the other tests. During the 21-year period, 369,780 bloodspot cards were received from male infants, of these 343,170 (92.8%) were screened using a bloodspot creatine kinase (CK) assay following parental consent. A total of 145 cases had a raised CK activity (≥250 U/l) and at follow-up, at 6-8 weeks of age, 79 cases had a normal serum CK (false-positive rate 0.023%) and 66 cases had an elevated serum CK. DMD was confirmed in 56 cases by genotyping/muscle biopsy studies, Becker muscular dystrophy in 5 cases and other rarer forms of muscular dystrophy in 5 cases. This long-term study has so far identified 13 false-negative cases. The incidence of DMD in Wales of 1:5136 during this period is lower than that of 1:4046 before commencement of screening in Wales. Screening has reduced the diagnostic delay enabling reproductive choice for parents of affected boys and earlier administration of current therapies.

An urgent need for a change in policy revealed by a study on prenatal testing for Duchenne muscular dystrophy

Prenatal diagnosis for Duchenne muscular dystrophy (DMD) was introduced in the Netherlands in 1984. We have investigated the impact of 26 years (1984-2009) of prenatal testing. Of the 635 prenatal diagnoses, 51% were males; nearly half (46%) of these were affected or had an increased risk of DMD. As a result 145 male fetuses were aborted and 174 unaffected boys were born. The vast majority (78%) of females, now 16 years or older, who were identified prenatally have not been tested for carrier status. Their average risk of being a carrier is 28%. We compared the incidences of DMD in the periods 1961-1974 and 1993-2002. The incidence of DMD did not decline but the percentage of first affected boys increased from 62 to 88%. We conclude that a high proportion of families with de novo mutations in the DMD gene cannot make use of prenatal diagnosis, partly because the older affected boys are not diagnosed before the age of five. Current policy, widely accepted in the genetic community, dictates that female fetuses are not tested for carrier status. These females remain untested as adults and risk having affected offspring as well as progressive cardiac disease. We see an urgent need for a change in policy to improve the chances of prevention of DMD. The first step would be to introduce neonatal screening of males. The next is to test females for carrier status if requested, prenatally if fetal DNA is available or postnatally even before adulthood.

Sleep disorders in boys with Duchenne muscular dystrophy

AIM

Determine the frequency and predictors of sleep disorders in boys with Duchenne Muscular Dystrophy (DMD).

METHOD

Cross-sectional study by postal questionnaire. Sleep disturbances were assessed using the Sleep Disturbance Scale for Children (validated on 1157 healthy children). A total sleep score and six sleep disturbance factors representing the most common sleep disorders were computed. Potential associations between pathological scores and personal, medical and environmental factors were assessed.

RESULTS

Sixteen of 63 boys (25.4%) had a pathological total sleep score compared with 3% in the general population. The most prevalent sleep disorders were disorders of initiating and maintaining sleep (DIMS) 29.7%, sleep-related breathing disorders 15.6% and sleep hyperhydrosis 14.3%. On multivariate analysis, pathological total sleep scores were associated with the need to be moved by a carer (OR = 9.4; 95%CI: 2.2-40.7; p = 0.003) and being the child of a single-parent family (OR =7.2; 95%CI: 1.5-35.1; p = 0.015) and DIMS with the need to be moved by a carer (OR = 18.0; 95%CI: 2.9-110.6; p = 0.002), steroid treatment (OR = 7.7; 95%CI: 1.4-44.0; p = 0.021) and being the child of a single-parent family (OR = 7.0; 95%CI: 1.3-38.4; p = 0.025).

CONCLUSION

Sleep disturbances are frequent in boys with DMD and are strongly associated with immobility. Sleep should be systematically assessed in DMD to implement appropriate interventions.

A population-based study of dystrophin mutations in Canada

INTRODUCTION

We carried out a population-based study of dystrophin mutations in patients followed by members of the Canadian Paediatric Neuromuscular Group (CPNG) over a ten-year period.

OBJECTIVES

We aimed to describe the changes in diagnostic testing for dystrophinopathy and to determine the frequency of dystrophin mutations from 2000 to 2009.

METHODS

De-identified data containing the clinical phenotypes, diagnostic methods, and mutational reports from dystrophinopathy patients followed by CPNG centres from January 2000 to December 2009 were analyzed using descriptive statistics.

RESULTS

773 patients had a confirmed diagnosis of dystrophinopathy based on genetic testing (97%), muscle biopsy (2%), or family history (1%). 573 (74%) had complete deletion/duplication analysis of all 79 exons or whole gene sequencing, resulting in 366 (64%) deletions, 64 (11%) duplications, and 143 (25%) point mutations. The percentage of patients who were diagnosed using currently accepted genetic testing methods varied across Canada, with a mean of 63% (SD 23). 246 (43%) mutations involved exons 45 to 53. The top ten deletions (n=147, 26%) were exons 45-47, 45-48, 45, 45-50, 45-55, 51, 45-49, 45-52, 49-50, and 46-47. 169 (29%) mutations involved exons 2 to 20. The most common duplications (n=29, 5.1%) were exons 2, 2-7, 2-17, 3-7, 8-11, 10, 10-11, and 12.

CONCLUSION

This is the most comprehensive report of dystrophin mutations in Canada. Consensus guidelines regarding the diagnostic approach to dystrophinopathy will hopefully reduce the geographical variation in mutation detection rates in the coming decade.

Moving towards meaningful measurement: Rasch analysis of the North Star Ambulatory Assessment in Duchenne muscular dystrophy

AIM

Reliable measurement of disease progression and the effect of therapeutic interventions in Duchenne muscular dystrophy (DMD) require clinically meaningful and scientifically sound rating scales. Therefore, we need robust evidence to support such tools. The North Star Ambulatory Assessment (NSAA) is a promising, clinician-rated scale with potential uses spanning clinical practice and clinical trials. In this study, we used Rasch analysis to test its suitability in these roles as a measurement instrument.

METHOD

NSAA data from 191 ambulant boys (mean age at assessment 7 y 8 mo, SD 2 y 4 mo; range 3 y 6 mo-15 y 5 mo) with a confirmed diagnosis of DMD were examined for psychometric properties including clinical meaning, targeting, response categories, model fit, reliability, dependency, stability, and raw to interval-level measurement. All analyses were performed using the Rasch Unidimensional Measurement Model.

RESULTS

Overall, Rasch analysis supported the NSAA as being a reliable (high Person Separation Index of 0.91) and valid (good targeting, little misfit, no reversed thresholds) measure of ambulatory function in DMD. One item displayed misfit (lifts head, fit residual 6.9) and there was evidence for some local dependency (stand on right/left leg, climb and descend box step right/left leg, and hop on right/left leg, residual correlations >0.40), which we provide potential solutions for in future use of the NSAA. Importantly, our findings supported good clinical validity in that the hierarchy of items within the scale produced by the analyses was supported by clinical opinion, thus increasing the clinical interpretability of scale scores.

INTERPRETATION

In general, Rasch analysis supported the NSAA as a psychometrically robust scale for use in DMD clinical research and trials. This study also demonstrates how Rasch analysis is a useful instrument to detect and understand the key measurement issues of rating scales.

Duchenne muscular dystrophy: a 30-year population-based incidence study

Duchenne muscular dystrophy (DMD) is among the most common lethal genetic diseases. It has been proposed that genetic counseling and prenatal diagnosis have begun to lower the incidence. We reviewed the records of all patients with confirmed DMD who were born between 1969 and 2008. Statistics Canada data on annual male births in Nova Scotia were obtained for each year.The overall incidence of 1 per 4700 male births remained stable during the 30-year period of the study. Similarly, the age at diagnosis did not change during that time.

Contiguous gene deletion syndrome in a female with ornithine transcarbamylase deficiency

OTC deficiency, a partially dominant X-linked trait, is the most frequent inborn error of the urea cycle. We describe a female patient with a contiguous gene deletion syndrome encompassing the OTC, DMD, RPGR, CYBB and XK genes, amongst others, only manifesting features of OTC deficiency. Molecular characterization was ascertained by MLPA and confirmed by CGH microarray, which revealed an 8.7 Mb deletion of the X-chromosome. Complete de novo deletion of the OTC gene led to a severe clinical phenotype in the proband. The application of high resolution molecular genetic techniques such as MLPA and array CGH, in mutation negative OTC cases allows the identification of chromosomal rearrangements, such as large deletions and provides information for accurate genetic counseling and prenatal diagnosis.

Diagnosis and management of Duchenne muscular dystrophy, part 1: diagnosis, and pharmacological and psychosocial management

Duchenne muscular dystrophy (DMD) is a severe, progressive disease that affects 1 in 3600-6000 live male births. Although guidelines are available for various aspects of DMD, comprehensive clinical care recommendations do not exist. The US Centers for Disease Control and Prevention selected 84 clinicians to develop care recommendations using the RAND Corporation-University of California Los Angeles Appropriateness Method. The DMD Care Considerations Working Group evaluated assessments and interventions used in the management of diagnostics, gastroenterology and nutrition, rehabilitation, and neuromuscular, psychosocial, cardiovascular, respiratory, orthopaedic, and surgical aspects of DMD. These recommendations, presented in two parts, are intended for the wide range of practitioners who care for individuals with DMD. They provide a framework for recognising the multisystem primary manifestations and secondary complications of DMD and for providing coordinated multidisciplinary care. In part 1 of this Review, we describe the methods used to generate the recommendations, and the overall perspective on care, pharmacological treatment, and psychosocial management.

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.

Adherence to american academy of pediatrics recommendations for cardiac care among female carriers of duchenne and becker muscular dystrophy

OBJECTIVE

The goal was to assess women's knowledge and heart health behaviors consistent with the American Academy of Pediatrics recommendations for cardiac care among female carriers of Duchenne/Becker muscular dystrophy.

METHODS

Using an advocacy group mailing list and working with 50 Muscular Dystrophy Association clinics, we surveyed women who had given birth to a son with Duchenne/Becker muscular dystrophy, thought that they were definitely or probably (>/=50% likelihood) a Duchenne/Becker muscular dystrophy carrier, or both. Self-report data classified respondents as carriers, noncarriers, or women with unknown status.

RESULTS

The respondents included 833 Duchenne/Becker muscular dystrophy carriers, 376 noncarriers, and 192 women with unknown status. Carriers were more likely than noncarriers and women in the unknown-status group to have ever undergone electrocardiography or other heart testing and to have seen a cardiologist in the past year, but they were not more likely to report a recent blood pressure or cholesterol level check. Only 64.4% of the carriers had ever had a heart test; 18.3% had seen a cardiologist in the past year. Only 62.9% of the carriers were aware of their cardiomyopathy risks before participating in the survey; 69.3% had informed their health care provider of their carrier status. Among carriers who had informed their provider, 70.2% had ever had a heart test and 21.4% had seen a cardiologist in the past year. In adjusted logistic regression models, factors that significantly increased the likelihood among carriers of ever having had a heart test and seeing a cardiologist in the previous year included older age (>/=50 years), feeling informed about their cardiomyopathy risks before the survey, and having told their provider about their carrier status.

CONCLUSION

More health education efforts are needed for both patients and their providers, to improve adherence to the American Academy of Pediatrics cardiac care guidelines for female Duchenne/Becker muscular dystrophy carriers.

Does familiarity breed acceptance? The influence of policy on physicians' attitudes toward newborn screening programs

OBJECTIVE

As newborn screening (NBS) programs expand to include conditions that challenge traditional public health criteria, little is known about what influences physicians' attitudes toward screening. We examined the effect of state policy and perceived state policy on pediatricians' attitudes toward screening.

METHODS

Six hundred pediatricians from the American Academy of Pediatrics who practiced in Wisconsin, Colorado, Florida, or Illinois were queried about (1) testing high-risk infants and (2) universal NBS for cystic fibrosis (CF), glucose-6-phosphate dehydrogenase deficiency (G6PD), and type 1 diabetes.

RESULTS

A total of 225 (41%) of 548 eligible pediatricians returned 223 surveys with usable data. The majority were supportive of NBS for CF (n = 188 [84%]) and G6PD (n = 130 [58%]), whereas only 25% (n = 55) supported type 1 diabetes screening. Pediatricians who lived in states that screen for a condition were more likely to support screening than those who lived in states that did not (CF: 117 of 119 [98%] vs 71 of 89 [80%]; type 1 diabetes: 32 of 88 [36%] vs 23 of 109 [21%]). Physicians also were more likely to support NBS when they believed that it was offered in their state versus when they believed that it was not (CF: 117 of 119 [98%] vs 52 of 65 [80%]; G6PD: 28 of 32 [88%] vs 75 of 108 [69%]; type 1 diabetes: 7 of 14 [50%] vs 25 of 102 [25%]).

CONCLUSIONS

Most pediatricians are supportive of NBS for CF and G6PD but not type 1 diabetes. Pediatricians who live in states that screen or believe that their states screen are more likely to support screening.

Attitudes and beliefs of pediatricians and genetic counselors regarding testing and screening for CF and G6PD: Implications for policy

There is wide variability in conditions included in state newborn screening (NBS) panels. The American College of Medical Genetics (ACMG) was commissioned by Health Resources and Services Administration to develop a uniform NBS panel. Based on survey data, the ACMG committee proposed a panel that included cystic fibrosis (CF) and glucose-6-phosphate dehydrogenase deficiency (G6PD), although G6PD was excluded from their final recommendations. We examine the attitudes of pediatricians and genetic counselors concerning screening for these two conditions. Data were collected as part of two different studies. Koopmans and Ross surveyed a random sample of 600 pediatricians from four states based on their NBS panels. Hiraki et al. surveyed genetic counselors who were members of the National Society of Genetic Counselors (NSGC) listserv. For this analysis, we compare the health care professionals' (HCPs') attitudes toward a universal NBS program for CF and G6PD, and how their support is influenced by state policy and personal interest in testing their own children. Two hundred twenty-three pediatricians and 267 genetic counselors provided partial or complete responses. Pediatricians are more likely to support NBS for both CF (84%) and G6PD (58%) than genetic counselors (56%, P < 0.001 and 39%, P < 0.001, respectively). Both pediatricians and genetic counselors' attitudes toward screening correlate with interest in screening their own children (P < 0.001). Interest in CF screening also correlates with state policy (pediatricians, P < 0.001; genetic counselors, P < 0.025). The correlation of professional recommendations with state policies and personal preferences reinforces the need for systematic evidence-based reviews rather than reliance on stakeholder opinions for developing national guidelines.

Population genetic screening programmes: principles, techniques, practices, and policies

This paper examines the professional and scientific views on the principles, techniques, practices, and policies that impact on the population genetic screening programmes in Europe. This paper focuses on the issues surrounding potential screening programmes, which require further discussion before their introduction. It aims to increase, among the health-care professions and health policy-makers, awareness of the potential screening programmes as an issue of increasing concern to public health. The methods comprised primarily the review of the existing professional guidelines, regulatory frameworks and other documents related to population genetic screening programmes in Europe. Then, the questions that need debate, in regard to different types of genetic screening before and after birth, were examined. Screening for conditions such as cystic fibrosis, Duchenne muscular dystrophy, familial hypercholesterolemia, fragile X syndrome, hemochromatosis, and cancer susceptibility was discussed. Special issues related to genetic screening were also examined, such as informed consent, family aspects, commercialization, the players on the scene and monitoring genetic screening programmes. Afterwards, these questions were debated by 51 experts from 15 European countries during an international workshop organized by the European Society of Human Genetics Public and Professional Policy Committee in Amsterdam, The Netherlands, 19-20, November, 1999. Arguments for and against starting screening programmes have been put forward. It has been questioned whether genetic screening differs from other types of screening and testing in terms of ethical issues. The general impression on the future of genetic screening is that one wants to 'proceed with caution', with more active impetus from the side of patients' organizations and more reluctance from the policy-makers. The latter try to obviate the potential problems about the abortion and eugenics issues that might be perceived as a greater problem than it is in reality. However, it seems important to maintain a balance between a 'professional duty of care' and 'personal autonomy'.

Developmental progress in Duchenne muscular dystrophy: lessons for earlier detection

OBJECTIVE

To address the issue of diagnostic delay in Duchenne Muscular Dystrophy (DMD) using developmental data from a cohort of affected boys detected by newborn screening and data on the diagnostic pathways of a group of boys diagnosed clinically.

DESIGN

Quantitative and semi-qualitative.

SETTING

Primary care.

SUBJECTS

1. Cohort of boys diagnosed by newborn screening (NBS cohort), 2. Group of mothers whose sons were diagnosed clinically (LCD group) Interventions. NBS cohort: (a) Developmental milestones, (b) Griffiths assessment, (c) clinic letters, (d) family case studies. LCD group: semi-structured interview.

MAIN OUTCOME MEASURE

1. The effectiveness of previously proposed strategies for the earlier clinical diagnosis of DMD. 2. Diagnostic pathways of the LCD group. Factors contributing to diagnostic delay in the LCD group.

RESULTS

1. Previously proposed strategies for earlier diagnosis would have had limited effectiveness in detecting the NBS cohort. 2. Diagnostic delay continues because: (a) initial observations are usually non-specific and made by the family, (b) age of presentation and presenting symptoms are highly variable, (c) first concerns are usually expressed to the primary care team who are less likely to recognise the early indicators, (d) early locomotor symptoms could suggest an orthopaedic rather than a paediatric referral.

CONCLUSIONS

The identification and implementation of an effective screening tool to reduce diagnostic delay is more complex than previously portrayed. In the light of this evidence service providers need to ask whether newborn screening is the only feasible solution to diagnostic delay.

Principles and performance: assessing the evidence

Despite the apparent rigour of the systematic review process there are a number of reasons why it may not accurately reflect the true state of current knowledge. For inborn errors of intermediary metabolism in general, the formal quality of literature on treatment is poor, partly because the rarity of the conditions makes systematic study difficult, partly because of the self-evident evidence paradox with treatments that are so obviously life-saving, and partly because of the widespread use of biochemical normalisation as a proxy outcome. In the field of newborn screening there is a paucity of formal trials so that assessment must be either by the 'causal pathway' approach or by reference to screening "criteria". The causal pathway approach may be misleading in that there are discontinuities, for example in projecting from known incidence (clinically diagnosed cases) to the incidence expected on screening. The criteria-based approach suffers from qualitative descriptors, such as "important" and "adequate", with no clear end-points, whilst in the context of neonatal screening some of the Wilson and Jungner criteria conflict with current evidence-based views. These problems are illustrated by reference to two reviews recently produced as part of the UK Health Technology Assessment Programme.

Population newborn screening for inherited metabolic disease: current UK perspectives

Some of the generally accepted criteria for screening programmes are inappropriate for newborn metabolic screening as they ignore the family dimension and the importance of timely genetic information. Uncritical application of such criteria creates special difficulties for screening by tandem mass spectrometry, which can detect a range diseases with widely different natural histories and responsiveness to treatment. Further difficulties arise from increasing demands for direct proof of the effects of screening on long-term morbidity and mortality. The randomized controlled trial is held to be the gold standard, but for ethical and practical reasons it will be impossible to achieve for such relatively rare diseases. This approach also oversimplifies the complex matrix of costs and benefits of newborn metabolic screening. A more workable approach could involve Bayesian synthesis, combining quantitative performance data from carefully designed prospective pilot studies of screening with existing experience of the natural history, diagnosis, and management of the individual disorders concerned.