Screening for Duchenne muscular dystrophy: an improved screening test for creatine kinase and its application in an infant screening program

Newborn screening and rapid genomic diagnosis of neuromuscular diseases

BackgroundIn recent years, treatments have been approved for certain neuromuscular diseases. In some cases, early pre-symptomatic treatment is necessary for optimal response, and thus newborn screening is critical.ObjectiveTo review the current status of newborn screening programs for neuromuscular diseases and early diagnosis through genetic testing.MethodsFollowing the PRISMA guidelines, a literature search was performed on PubMed for screening of neuromuscular diseases; the search was conducted on literature available as of 1 May 2024.ResultsIncluded were 77 articles on newborn screening for seven diseases: spinal muscular atrophy (19 studies), Duchenne muscular dystrophy (15), Pompe disease (20), X-linked adrenoleukodystrophy (14), Krabbe disease (6), metachromatic leukodystrophy (2), and myotonic dystrophy 1 (1). Ten articles on rapid genomic diagnosis were identified.ConclusionSince 2021, newborn screening programs for neuromuscular diseases have been established, notably in X-linked adrenoleukodystrophy, spinal muscular atrophy, Pompe disease, and Duchenne Muscular Dystrophy. Even in diseases where treatment is currently not life-changing, such as Krabbe disease, new newborn screening programs continue to be implemented, especially in the USA. The use of genetic diagnostic tests does not yet appear to be widespread or at least not widely reported. As new treatments become available, genomic newborn screening programs will need to be rapidly and broadly implemented.

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.

A pilot study of newborn screening for Duchenne muscular dystrophy in Guangzhou

Background

To estimate the overall situation of Duchenne muscular dystrophy (DMD) screening in newborns in Guangzhou, China.

Method

A total of 62553 newborns including 44268 males and 18285 females were screened for DMD by measuring muscle specific creatine kinase isoform (CK-MM) concentrations using the GSP® Neonatal CK-MM kit based on time-resolved immunofluorescence. We recalled positive cases and recollected dried blood spots (DBS) for retest of CK-MM. The newborns with retest positive result were recalled again for serum creatine kinase (CK) and multiplex ligation-dependent probe amplification (MLPA) test. Whole exon sequencing was performed when MLPA test was negative.

Results

Four males were diagnosed with DMD. The incidence of males was 1/11067. No DMD patient was found in female. There were significant differences of CK-MM concentration between male and female newborns. Among gestational age (GA), birth weight (BW) and age at sampling, linear regression analysis showed that CK-MM concentration was much more closely correlated with GA and age at sampling.

Conclusions

CK-MM concentration is affected by gender, GA, BW and age at sampling. The efficiency of DMD screening might be improved by adjusting a multitier cut-off value according to GA and age at sampling. DMD newborn screening should be male priority.

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A total of 62553 newborns including 44268 males and 18285 females were screened for DMD in Guangzhou.

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Four males were diagnosed with DMD. The incidence of males was 1/11067. No DMD patient found in female.

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DMD newborn screening should be male priority.

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The efficiency of DMD screening might be improved by adjusting a multitier cut-off value according to GA and age at sampling.

Creatine kinase-MM concentration in dried blood spots from newborns and implications for newborn screening for Duchenne muscular dystrophy

Introduction/Aims

Creatine kinase‐MM (CK‐MM) is a marker of skeletal muscle damage. Detection of elevated levels of CK‐MM in newborns can enable an early suspicion of the diagnosis of Duchenne muscular dystrophy (DMD) before symptom onset. Our aim was to investigate CK‐MM levels in DMD‐affected and unaffected newborns using an immunoassay that measures CK‐MM concentration in dried blood spots collected for routine newborn screening.

Methods

To validate the assay in our laboratory, CK‐MM measurements and newborn demographic information were collected for 8584 de‐identified specimens and 15 confirmed DMD patients. After analyzing validation data, CK‐MM normal ranges were determined based on age of newborn at specimen collection. Subsequently, the assay was used to measure CK‐MM concentration in 26 135 newborns as part of a consented pilot study to screen for DMD in New York State. Mean and median levels of CK‐MM based on age of collection, in addition to the 2.5th, 50th, 97.5th, and 99.5th percentiles, were recalculated using the validation and screening data sets.

Results

Median CK‐MM within 1 hour of birth was 109 ng/mL, rose to a high of 499 ng/mL at 25 hours of age, and then declined to 200 ng/mL at 2 days of life. The median continued to decline more slowly and then stabilized at approximately 40 ng/mL at 1 week of life.

Discussion

Because of the marked variability and elevated CK‐MM levels observed within the first days of life, it is important to set multiple CK‐MM age‐related cut‐offs when screening for DMD in newborns.

Creatine kinase test diagnostic accuracy in neonatal screening for Duchenne Muscular Dystrophy: A systematic review

OBJECTIVES

to evaluate the accuracy of the creatine kinase test in neonatal screening for Duchenne Muscular Dystrophy.

METHODS

Investigations were carried out in six databases, gray literature and manual search. All studies and data extraction eligibility processes were carried out in paired mode. The methodological stringency of the studies was assessed using the modified QUADAS 2 tool. The performance measures of the test were calculated using the Meta-DiSc software, version 1.4.

RESULTS

11 studies were included, with a total sample of 1,416,123 newborns. The positive likelihood ratio was more than 10 in these studies. On the other hand, the negative likelihood ratio was up to 0.2 in 9/10 studies; however, when considering the upper limit of the confidence interval, only 4/10 studies showed a negative likelihood ratio less than 0.2 and in 6/11 it was greater than 0.5. Specificity was close to 1 in studies. The sensitivity was equal to or greater than 0.81 in 10/11 studies; however, when considering the reliability's minimum interval limit, only 6/10 studies showed sensitivity equal to or greater than 0.7. Ten studies were summarized on a ROC curve indicating good performance (Area under the curve = 0.9980 and Q index = 0.9846).

CONCLUSIONS

the creatine kinase test showed good accuracy in screening for cases of Duchenne Muscular Dystrophy and may be a useful alternative in the early diagnosis of the disease followed by confirmatory genetic testing.

Newborn screening of neuromuscular diseases

Neuromuscular diseases represent an heterogenous group of more than 400 diseases, with a very broad phenotypic spectrum. Given their rarity and complexity, neuromuscular diseases are often diagnosed with a very significant delay after which irreversible muscle damage may limit the efficacy of treatments when available. In this context, neonatal screening could constitute a solution for early detection and treatment. A systematic review of the literature in PubMed up to May 1, 2021, was conducted according to PRISMA guidelines, including classical neuromuscular diseases and diseases with a clear peripheral nervous system involvement (including central nervous system disease with severe neuropathy). We found seven diseases for which newborn screening data were reported: spinal muscular atrophy (9), Duchenne muscular dystrophy (9), Pompe disease (8), X-linked adrenoleukodystrophy (5), Krabbe disease (4), myotonic dystrophy type 1 (1), metachromatic leukodystrophy (1). The future of newborn screening for neuromuscular disorders pass through a global technological switch, from a biochemical to a genetic-based approach. The rapid development of therapy also requires the possibility to quickly adapt the list of treated conditions, to allow innovative therapies to achieve their best efficacy.

Applications of bioluminescence in biotechnology and beyond

Bioluminescent probes have hugely benefited from the input of synthetic chemistry and protein engineering. Here we review the latest applications of these probes in biotechnology and beyond, with an eye on current limitations and future directions.

Population-Wide Duchenne Muscular Dystrophy Carrier Detection by CK and Molecular Testing

Carrier screening of Duchenne muscular dystrophy (DMD) has not been widely evaluated. To identify definite DMD female carriers prior to or in early pregnancy, we studied a large population of reproductive age females and provided informed reproductive options to DMD carriers. 37268 females were recruited from the Hangzhou Family Planning Publicity and Technology Guidance Station/Hangzhou Health Service Center for Children and Women, Hangzhou, China, between October 10, 2017, and December 16, 2018. CK activity was measured with follow-up serum DMD genetic testing in subjects with hyperCKemia, defined as CK > 200 U/L. The calculated upper reference limit (97.5^th percentile) of serum creatine kinase (CK) for females aged 20-50 years in this study was near the reference limit recommended by the manufacturer (200 U/L), above which was defined as hyperCKemia. 427 females (1.2%) harbored initially elevated CK, among which 281 females (response rate of 65.8%) accepted CK retesting. DMD genetic testing was conducted on 62 subjects with sustained serum CK > 200 U/L and 16 females with a family history of DMD. Finally, 6 subjects were confirmed to be DMD definite carriers. The estimated DMD female carrier rate in this study was 1 : 4088 (adjusting for response rate), an underestimated rate, since only 50% to 70% of DMD female carriers manifest elevated serum CK, and carriers in this study may have been missed due to lack of follow-up or inability to detect all DMD pathogenic variants by current genetic testing.

Global epidemiology of Duchenne muscular dystrophy: an updated systematic review and meta-analysis

Background

Duchenne Muscular Dystrophy (DMD) is a rare disorder caused by mutations in the dystrophin gene. A recent systematic review and meta-analysis of global DMD epidemiology is not available. This study aimed to estimate the global overall and birth prevalence of DMD through an updated systematic review of the literature.

Methods

MEDLINE and EMBASE databases were searched for original research articles on the epidemiology of DMD from inception until 1st October 2019. Studies were included if they were original observational research articles written in English, reporting DMD prevalence and/or incidence along with the number of individuals of the underlying population. The quality of the studies was assessed using a STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) checklist adapted for observational studies on rare diseases. To derive the pooled epidemiological prevalence estimates, a meta-analysis was performed using random-effects logistic models for overall and birth prevalence and within two different underlying populations (i.e. all individuals and in males only), separately. Heterogeneity was assessed using Cochran’s Q-test along with its derived measure of inconsistency I².

Results

A total of 44 studies reporting the global epidemiology of DMD were included in the systematic review and only 40 were included in the meta-analysis. The pooled global DMD prevalence was 7.1 cases (95% CI: 5.0–10.1) per 100,000 males and 2.8 cases (95% CI: 1.6–4.6) per 100,000 in the general population, while the pooled global DMD birth prevalence was 19.8 (95% CI:16.6–23.6) per 100,000 live male births. A very high between-study heterogeneity was found for each epidemiological outcome and for all underlying populations (I² > 90%). The test for funnel plot asymmetry suggested the absence of publication bias. Of the 44 studies included in this systematic review, 36 (81.8%) were assessed as being of medium and 8 (18.2%) of low quality, while no study was assessed as being of high quality.

Conclusions

Generating epidemiological evidence on DMD is fundamental to support public health decision-making. The high heterogeneity and the lack of high quality studies highlights the need to conduct better quality studies on rare diseases.

Genetic and genomic analysis for cocoon yield traits in silkworm

Domestic species provides a powerful model for examining genetic mechanisms in the evolution of yield traits. The domestic silkworm (Bombyx mori) is an important livestock species in sericulture. While the mechanisms controlling cocoon yield are largely unknown. Here, using B. mori and its wild relative B. mandarina as intercross parents, 100 BC₁ individuals were sequenced by restriction site-associated DNA sequencing (RAD-Seq). The linkage map contained 9,632 markers was constructed. We performed high-resolution quantitative trait locus (QTL) mapping for four cocoon yield traits. A total of 11 QTLs were identified, including one yield-enhancing QTL from wild silkworm. By integrating population genomics and transcriptomic analysis with QTLs, some favourable genes were revealed, including 14 domestication-related genes and 71 differentially expressed genes (DEGs) in the fifth-instar larval silk gland transcriptome between B. mori and B. mandarina. The relationships between the expression of two important candidate genes (KWMTBOMO04917 and KWMTBOMO12906) and cocoon yield were supported by quantitative real-time PCR (qPCR). Our results provide some new insights into the molecular mechanisms of complex yield traits in silkworm. The combined method might be an efficient approach for identifying putative causal genes in domestic livestock and wild relatives.

A Historical and Current Review of Newborn Screening for Neuromuscular Disorders From Around the World: Lessons for the United States

BACKGROUND

We aimed to review the history of newborn screening for three neuromuscular disorders (Duchenne muscular dystrophy, Pompe disease, and spinal muscular atrophy [SMA]) to determine best practices.

METHODS

The history of newborn screening for Duchenne muscular dystrophy began in 1975 with the measurement of creatinine kinase on newborn male blood spots from two Midwestern hospitals in the United States. Over the next 40 years, ten programs were implemented around the globe although none currently remain. The first experimental pilot program for Pompe disease began in 2005 in Taiwan. In 2013, Missouri was the first US state to implement Pompe newborn screening before its inclusion in the Recommended Uniform Screening Panel (RUSP) in 2015 by the Advisory Committee on Heritable Disorders in Newborns and Children (United States). In 2008, SMA was reviewed and rejected for inclusion in the RUSP because no treatment existed. With the approval of nusinersen in late 2016, spinal muscular atrophy is being reconsidered for the RUSP.

RESULTS

A condition should meet public health screening criteria to be included in the RUSP. Duchenne muscular dystrophy, Pompe, and SMA challenge traditional screening criteria: Duchenne muscular dystrophy does not present in infancy and lacks effective treatment; Pompe and SMA may not present until adulthood; and safety and efficacy of long-term intrathecal treatment for SMA is unknown. Potential reproductive benefit and improved research recruitment do not justify a public health screening program.

CONCLUSIONS

This review provides lessons that could benefit US public health departments as they consider expanding screening to include neuromuscular disorders like Duchenne muscular dystrophy, Pompe, and SMA.

Screening for Duchenne muscular dystrophy in Germany, 1977-2011: A personal story

EDITOR'S NOTE

This article by Dr. Günter Scheuerbrandt is a fascinating personal account and historical narrative of the birth and development of a screening program for Duchenne Muscular Dystrophy in Germany, beginning 40 years ago. As the author notes, approval of an institutional review board or ethics committee was not required for this type of scientific investigation in one's field at the time this program was begun, but we have removed all personal data from any of the materials presented in here in order to conform to current concepts of ethical publication. This article is about the screening of 528,410, mostly 4-6-week-old, boys in Germany between 1977 and 2011 for high levels of creatine kinase (CK) to identify those with Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). During these 34 years of infant screening, 147 boys with confirmed, probable, and possible DMD (incidence 1:3,600 male births) and 33 boys with confirmed, probable, and possible BMD (incidence 1:15,500 male births) were found. Research reports about DMD were sent to families and pediatricians participating in the screening, and, on request, to families and scientists everywhere. It is hoped that screening programs used as the basis for future therapies will be able to modify the natural history of boys with DMD. New dystrophin mutations will continue to occur, necessitating screening and early therapy. Abstract Submitted for Presentation at the 10th International Society for Neonatal Screening-Asia Pacific Regional Meeting, August 2017, Ulaanbataar, Mongolia. Muscle Nerve 57: 185-188, 2018.

Characterization of a Blood Spot Creatine Kinase Skeletal Muscle Isoform Immunoassay for High-Throughput Newborn Screening of Duchenne Muscular Dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a progressive, lethal X-linked neuromuscular disorder with an average worldwide incidence of 1:5000. Blood spot creatine kinase (CK) enzyme assays previously used in newborn screening programs for DMD are nonspecific because measured CK enzyme activity is attributable to 3 isoenzyme forms of CK (CK-MM, CK-MB, and CK-BB) and it is the CK-MM isoform that is found predominantly in skeletal muscle. CK-MM is increased in boys with DMD owing to muscle damage. We describe a sensitive and specific automated immunoassay for CK-MM to screen for DMD in blood spots.

METHODS

The prototype assay was developed on the PerkinElmer GSP® analyzer to enable high-throughput screening. CK-MM was assayed using a solid phase, 2-site immunofluorometric system. Purified human CK-MM was used to create calibrators and controls.

RESULTS

The limit of blank (LOB), detection (LOD), and quantification (LOQ) values were <1, 3, and 8 ng/mL, respectively. The analytical measurement range was 4–8840 ng/mL. Interassay (n = 40) imprecision was <7% across the analytical range. Cross-reactivity was <5% for CK-MB and 0% for CK-BB. The mean recovery of CK-MM was 101% (range 87%–111%). Blood spots from newborn infants (n = 277) had a mean CK-MM concentration of 155 ng/mL and a 99th centile of 563 ng/mL. The mean blood spot CK-MM concentration from 10 cases of DMD was 5458 ng/mL (range 1217–9917 ng/mL).

CONCLUSIONS

CK-MM can be reliably quantified in blood spots. The development of this CK-MM assay on a commercial immunoassay analyzer would enable standardized and high-throughput newborn blood spot screening of DMD.

Creatine kinase in human erythrocytes: A genetic anomaly reveals presence of soluble brain-type isoform

For maintaining energy homeostasis, creatine kinase (CK) is present at elevated levels in tissues with high and/or fluctuating energy requirements such as muscle, brain, and epithelia, while there is very few CK, if any, in peripheral blood cells. However, an ectopic expression of brain-type creatine kinase (BCK) has been reported for platelets and leukocytes in an autosomal dominant inherited anomaly named CKBE. Here we investigated CK in erythrocytes of CKBE individuals from eight unrelated families. The data revealed a varying but significant increase of CK activity in CKBE individuals as compared to controls, reaching an almost 800-fold increase in two CKBE individuals which also had increased erythrocyte creatine. Immunoblotting with highly specific antibodies confirmed that the expressed CK isoform is BCK. Cell fractionation evidenced soluble BCK, suggesting cytosolic and not membrane localization of erythrocyte CK as reported earlier. These results are discussed in the context of putative CK energy buffering and transfer functions in red blood cells.

Optimization of the firefly luciferase reaction for analytical purposes

The optimization of assays has two purposes: (1) to increase the sensitivity of the assay so that low levels of the analyte can be determined; and (2) to prevent small changes of the reaction conditions from having a large impact on the outcome of the assay. The two purposes are usually equally important, as has been recognized in well-established branches of analytical chemistry, such as clinical chemistry. The firefly luciferase reaction can be used for many types of assays. The way to optimize these assays is not trivial, as there are many parameters to consider. Furthermore, as there are now several types of recombinant luciferases available, one has to decide which is the most suitable for each individual assay. The optimization is influenced by the conditions and requirements under which the assay is performed. Special attention is given to ways to calibrate assays. Examples on optimization are mainly taken from the author's own work during 40 years using assays based on the firefly luciferase reaction.

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.

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.

Clinic-based infant screening for duchenne muscular dystrophy: a feasibility study

Purpose. The purpose of this study was to assess the desirability of Duchenne muscular dystrophy (DMD) screening, the effectiveness of the consent process, and the feasibility of conducting DMD screening in a pediatric office. Methods. Infant males who attended a 12-month routine well-child visit at a participating pediatric clinic were screened for DMD. Parents and providers completed post-screening questionnaires to assess their experiences with and attitudes toward screening. Results. A total of 264 male infants were screened for DMD. Approximately 78% of parents indicated support of voluntary DMD screening and 91% of providers were in favor of screening for DMD. About 75% of parents correctly answered three of five questions testing their knowledge of DMD screening. Conclusion. DMD screening is feasible in a pediatric office when conducted as part of a research study. Infant screening for DMD eventually could be offered in pediatric health care provider offices as an optional public health service outside of newborn screening.

High levels of brain-type creatine kinase activity in human platelets and leukocytes: a genetic anomaly with autosomal dominant inheritance

The ectopic expression in peripheral blood cells of the brain-type creatine kinase (CKB) is an autosomal dominant inherited anomaly named CKBE (MIM ID 123270). Here, we characterized the CK activity in serum, platelets (PLT) and leukocytes (WBC) of 22 probands (from 8 unrelated families) and 10 controls. CK activity was measured by standard UV-photometry. Expression of the CKB gene was analyzed by real-time PCR and Western blotting. DNA sequencing including bisulfite treatment was used for molecular analysis of the CKB gene. Serum CK levels were comparable between probands and controls. CKBE probands revealed significantly higher CK activity in PLT (3.7 ± 2.7 versus 179.2 ± 83.0 U/10(12) PLT; p<0.001) and WBC (0.4 ± 0.3 versus 2.6 ± 2.1 U/10(9) WBC; p=0.004). Inhibitory anti-CKM antibodies did not affect CK activity indicating that the CK activity is generated exclusively by the CK-BB isoenzyme. CKB mRNA and protein levels were significantly higher in PLT and WBC from probands compared to controls. Re-sequencing of the entire CKB gene and methylation analysis of a CpG island revealed no alteration in CKBE probands. The genetic basis of CKBE remains unclear, however, we propose that a de-methylated CKB gene is inherited that leads to high CKB expression levels in myeloic precursor cells in the bone marrow.

Reconsidering reproductive benefit through newborn screening: a systematic review of guidelines on preconception, prenatal and newborn screening

The expansion of newborn screening (NBS) has been accompanied by debate about what benefits should be achieved and the role of parental discretion in their pursuit. The opportunity to inform parents of reproductive risks is among the most valued additional benefits gained through NBS, and assumes prominence where the primary goal of identifying a treatable condition is not assured. We reviewed 53 unique guidelines addressing prenatal, preconception and newborn screening to examine: (1) how generating reproductive risk information is construed as a benefit of screening; and (2) what conditions support the realization of this benefit. Most preconception and prenatal guidelines - where generating reproductive risk information is described as a primary benefit - required that individuals be given a 'cascade of choices', ensuring that each step in the decision-making process was well informed, from deciding to pursue information about reproductive risks to deciding how to manage them. With the exception of three guidelines, NBS policy infrequently attended to the potential for reproductive benefits; further, most guidelines that acknowledged such benefits construed voluntarism narrowly, without attention to the choices attendant on receiving reproductive risk information. This review suggests that prenatal and preconception guidance identifies a coherent framework to support the pursuit of reproductive benefits through population screening programmes. Interestingly, attention to reproductive benefits is increasing among NBS guidance, yet reflection on how such benefits ought to be pursued remains limited. Traditional norms for NBS may require reconsideration where the remit of screening exceeds the primary goal of clinical benefits for infants.

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.

Duchenne muscular dystrophy: issues in expanding newborn screening

PURPOSE OF REVIEW

To illustrate potential risks and benefits of disease screening for newborns using the example of Duchenne muscular dystrophy.

RECENT FINDINGS

There is a wide range in the reported positive predictive value for screening male newborns for Duchenne muscular dystrophy by the creatine kinase level on dried blood spots. Some parental anxiety is associated with both early detection and false-positive screening results. No data are available about the impact of the diagnosis on the child, including the impact of early initiation of therapy. Studies suggest that few parents change their future reproductive planning based on identification of Duchenne muscular dystrophy through screening. Few data are available regarding the cost of newborn screening for Duchenne muscular dystrophy, and there are insufficient data to evaluate the cost-effectiveness of Duchenne muscular dystrophy screening.

SUMMARY

Available data are insufficient to recommend routine newborn screening for Duchenne muscular dystrophy. Understanding the gaps in knowledge provides insight into the evidence needed to recommend newborn screening for Duchenne muscular dystrophy. Studies are needed to evaluate the potential risks and benefits of screening, including the associated incremental costs.

Pediatricians' attitudes toward expanding newborn screening

OBJECTIVE

Traditional population screening focuses on conditions for which early treatment prevents severe morbidity and mortality. The classic example in pediatrics is newborn screening for phenylketonuria, which began in the 1960s. In 1968, Wilson and Jungner delineated 10 criteria that would justify population screening. These criteria have been reaffirmed by many newborn screening task forces as the standard for adding conditions to newborn screening programs. Today, however, some newborn screening programs are expanding to include conditions that may not meet all of the traditional screening criteria. Little is known about pediatricians' attitudes toward expanding screening. We examine the attitudes of pediatricians and pediatric subspecialists toward screening for cystic fibrosis (CF), Duchenne muscular dystrophy (DMD), fragile X, and type 1 diabetes.

METHODS

A cross-sectional survey was conducted of 600 pediatricians, including those who are members of the section of genetics, endocrinology, pulmonology, and neurology of the American Academy of Pediatrics. For each condition, pediatricians were queried about (1) testing high-risk infants, (2) newborn screening, and (3) population screening or testing beyond the newborn period. Demographic data were also collected.

RESULTS

A total of 232 (43%) of 537 eligible pediatricians returned surveys. More than 75% support testing high-risk infants for all conditions except type 1 diabetes. CF was the only condition for which >50% supported newborn screening. Newborn screening was preferred over screening older infants for all conditions except fragile X. Subspecialty affiliation did not have a significant impact with respect to attitudes about testing high-risk children, newborn screening, or screening beyond infancy. We analyzed the data by the number of patients with the queried condition under the physician's care and by the number of affected family members. Neither aspect was significant. We also analyzed the data by gender, by year of residency graduation, and by geographic location. None of these factors revealed significant differences in responses. For each condition, 8% to 41% of physicians would personally choose to test their own infant. We found that physicians' opinion about what they would want for their own children correlated with their attitude about population newborn screening. Those who would personally choose testing of their own infants were highly likely to support newborn screening for CF (98%), DMD (94%), and fragile X (98%), but only 78% of those who would personally opt for newborn screening of type 1 diabetes would also endorse population-based screening. This was statistically significant for each condition. Those who would choose not to test their own infants were significantly less likely to support newborn screening of the general population. One third of those who did not want to test their own newborns for CF supported population screening, whereas only one fifth supported DMD and fragile X population screening. For type 1 diabetes, 98% of those who would not personally choose newborn testing did not want it offered as a population screening program.

CONCLUSIONS

Most physicians support diagnostic genetic testing of high-risk children but are less supportive of expanding newborn screening, particularly for conditions that do not meet the Wilson and Jungner criteria. Willingness to expand newborn screening does not correlate with professional characteristics but rather with personal interest in testing of their own children.

Should children and adolescents undergo genetic testing?

Genetic testing comes in many shapes and sizes. The decision to undergo genetic testing must involve consideration of the medical, psychosocial, and reproductive benefits and risks of testing. The evaluation of risks and benefits varies significantly both between and within families. Pediatricians should keep up with the rapid advances in genetic medicine and the myriad of tests that are being developed and marketed. They also need to be familiar with the psychosocial risks and benefits that these new tests generate for individuals, families and communities. In some situations, genetic testing is merely another diagnostic tool; in other situations, genetic testing offers information about the risks for future diseases. Pediatricians need to be knowledgeable about tests that are indicated clinically and their potential psychosocial implications to best serve children, adolescents, and their families.

Rapid time-resolved immunofluorometric assay for the measurement of creatine kinase in serum and whole blood samples

A rapid and simple immunochemical method was developed for the assessment of the creatine kinase (MM) isoenzyme [CK(MM)], a protein marker linked with animal welfare and meat quality. The one-step time-resolved immunofluorometric assay produced quantitative results from serum or whole blood samples in 20 min. The analytical limit of detection (mean + 2s) for the immunoassay was 17 ng/mL (n = 6), and the functional limit of detection for the analysis of porcine whole blood samples was 426 ng/mL (n = 24). The working range of the method was linear up to 50 micro g/mL, and the within-assay precision varied between 2.1 and 10.9%. The analysis of porcine serum samples showed that the results from the immunoassay method and colorimetric CK enzyme activity determination were highly correlated (r(2) = 0.965, n = 17, p < 0.001). The practicability of the assay was demonstrated by the analysis of 300 porcine whole blood samples in a slaughterhouse environment.

Use of firefly luciferase in ATP-related assays of biomass, enzymes, and metabolites

The kinetics of ATP reagents not affected by product inhibition or other forms of inactivation of luciferase during the measurement time has been clarified. Under these conditions the decay rate of the light emission expressed as percentage per minute is a measure of luciferase activity and can be given as the rate constant k (min-1), directly reflecting the degradation of ATP in the luciferase reaction. Three types of reagents with different analytical characteristics and different application possibilities have been identified. Stable light-emitting reagents are suitable for measurements of ATP down to 1000 amol. This is the only type of reagent suitable for monitoring ATP-converting reactions, i.e., assays of enzymes or metabolites, assays of oxidative phosphorylation, photophosphorylation, and so on. A higher luciferase activity resulting in a slow decay of the light emission by approximately 10% per minute (k = 0.1 min-1) gives a reagent suitable for measurements down to 10-100 amol. The slow decay of light emission allows use of manual luminometers without reagent dispensers. A further increase of the luciferase activity resulting in a decay rate of approximately 235% per min (k = 2.35 min-1) and only 10% of the light emission remaining after 1 min is suitable for measurements down to 1 amol corresponding to half a bacterial cell. With this type of flash reagent the total light emission can be calculated from two measurements of the light intensity on the decay part of the light emission curve. This new measure is not affected by moderate variations in luciferase activity, but only by changes in quantum yield and self-absorption of the light in the sample. Flash-type reagents require the use of reagent dispensers. The stringent requirements for ATP-free cuvettes, pipette tips, and contamination-free laboratory techniques make it unlikely that flash reagents would be useful in nonlaboratory surroundings. A potential application for this type of reagent is sterility testing. In general, it is concluded that one should select the ideal ATP reagent carefully for each application. Obviously the reagents used in a particular application do not have to match the decay rates given earlier exactly. However, various applications of the ATP technology and the properties of manual and automatic luminometers fall quite nicely into categories corresponding to the properties of the three reagents described. The rapidly growing interest in ATP technology has already resulted in the development of a greater variety of luminometers, from hand-held instruments to high-throughput systems. The continuation of efforts in both reagent and instrument development will undoubtedly result in many new applications.

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.

Importance of lower limb surgery in Duchenne muscular dystrophy

A total of 123 patients with Duchenne muscular dystrophy (DMD) was surgically treated during two different periods of their course by hip and knee release, aponeurectomy of the iliotibial band and z-shaped Achilles' tendon lengthening. In 57 patients (group I) this was carried out prophylactically as retractions of the lower limb joints were just beginning at the age of 6.4 +/- 1.43 years and in 66 patients (group II) as mild contractures of the joints at the end of walking ability were already manifest with an average age of 9.27 +/- 1.86 years. The average follow-up was 3.7 +/- 1.2 years in both groups. To be able to assess the interindividual course of both groups, we defined "joint and motor quotients", which allowed a complex assessment of joint function and motoric capacity. In addition, both groups were compared with a control group (natural history) consisting of 100 non-operated DMD patients. In both groups a significant release of the contractures could be obtained primarily. Patients in group I showed a much better long-term effect than those in group II. The motor quotient in group I was significantly better over the whole follow-up period (P < 0.001) than in group II or the control group. The prolongation of walking ability by about 2 years compared with the natural history is in our opinion not the central goal of this surgical treatment concept of lower limbs in DMD, but rather the additionally achieved prolongation of an assisted standing ability with the lower limbs free from contractures and deformities.(ABSTRACT TRUNCATED AT 250 WORDS)

Cost-effectiveness of neonatal screening for Duchenne muscular dystrophy--how does this compare to existing neonatal screening for metabolic disorders?

Costs of screening a series of 18,152 newborn males for Duchenne muscular dystrophy (DMD) in Canada were evaluated. The final aim of neonatal screening for DMD is the avoidance of additional cases in the families identified. Total costs to avoid one case of DMD were estimated at Cdn. $172,000, while the incremental costs were found to be $83,000. Reagent costs, test sensitivity, efficacy of screening and compliance with genetic advice were identified as factors crucial for cost-effectiveness. Costs of neonatal screening for DMD are compared with costs of neonatal screening for inborn metabolic disorders. It is found that the two programmes are similar in costs. Earlier predictions of inordinate costs of screening for DMD are refuted.

Experience with screening newborns for Duchenne muscular dystrophy in Wales

OBJECTIVES

To assess the acceptability of screening newborn boys for Duchenne muscular dystrophy.

DESIGN

Screening is offered on the basis of informed consent in response to an information sheet entitled "A new test for baby boys--Do you want it?" The programme includes a prospective long term evaluation of family responses to early diagnosis and a comparison of their experiences and perceptions with those families who have undergone the later traditional clinical diagnosis.

SETTING

All maternity units throughout Wales. Samples obtained through screening programme for phenylketonuria and congenital hypothyroidism.

SUBJECTS

Those families whose son had a positive screening test.

MAIN OUTCOME MEASURES

Creatine kinase activity. Venous blood test to confirm positive result. Molecular genetic mutation analysis. Muscle biopsy and dystrophin analysis. Qualitative measure of satisfaction among affected families.

RESULTS

34,219 Boys have been screened and nine affected families have been identified. Eight families were very positive about the programme. Three chose not to complete the diagnostic process.

CONCLUSION

The programme should continue to permit a full evaluation of the issues involved and should serve as a model for other initiatives within the community for genetic disease.

Epidemiology of neuromuscular disorders in the under-20 population in Bologna Province, Italy

A retrospective epidemiological survey of the principal neuromuscular disorders was undertaken in the population under the age of 20 yr in Bologna city and province. The incidence of Duchenne muscular dystrophy (DMD) proved to be 25.8 x 10(-5), that is, comparable with the outcome of neonatal screening studies. The incidence of spinal muscular atrophy (SMA) was very high (11.2 x 10(-5), probably the result of our greater awareness and recognition of this disorder. The prevalence of neuromuscular disorders in the 0-19 yr population is 1.5 times that in the general population; that of DMD is 28 x 10(-5) vs 6.3 x 10(-5) and that of the SMA 6.5 x 10(-5) vs 1.2 x 10(-5). Our results indicate that neuromuscular disorders, particularly DMD and SMA I and II, have a much higher prevalence in the first two decades of life than is generally thought. Awareness of the higher prevalence of neuromuscular disorders among the under-20s is essential to the adequate planning of medical services.

Three years' experience with neonatal screening for Duchenne/Becker muscular dystrophy: gene analysis, gene expression, and phenotype prediction

Neonatal screening for Duchenne/Becker Muscular dystrophy (DMD/BMD) was begun as a pilot program on January 1, 1986. The aim of this program was to reduce the incidence of this X-linked recessive degenerative neuromuscular disease. The neonatal detection of a boy with DMD allows early identification of carriers and genetic counselling. This may avert the birth of other affected males born prior to clinical diagnosis of DMD in the propositus at about age 5 years. Between January 1, 1986, and December 31, 1988, we identified and characterized a cohort of 8 asymptomatic infant boys with grossly elevated levels of creatine kinase, an active primary dystrophic process of muscle and complete dystrophin deficiency. Five of 8 males have detectable DNA alterations involving the DMD/BMD locus. Based on current hypotheses, characterization of dystrophin expression of this cohort allows us to predict a DMD phenotype in all 8 boys. To date, no additional males with DMD have been born in these families. Prospective follow-up will allow us to test the validity of dystrophin testing in predicting the clinical course and impact of this program on reproductive decision making in these families.

Population frequencies of inherited neuromuscular diseases--a world survey

A survey of the world literature, involving over 150 reported studies, of the population frequencies of various inherited neuromuscular diseases has been carried out. Data are presented for the commoner forms of muscular dystrophy (Duchenne, Becker, facioscapulohumeral, limb girdle), myotonic dystrophy and congenital myotonias, proximal spinal muscular atrophies, and the hereditary motor and sensory neuropathies. A conservative estimate of the overall prevalence among both sexes is around 286 x 10(-6), that is 1 in 3500 of the population may be expected to have a disabling inherited neuromuscular disease presenting in childhood or in later life. If severe disorders manifest only in infancy and early childhood (e.g. Werdnig-Hoffmann disease and severe congenital muscular dystrophy) and the rare forms of dystrophy and myopathy are also included, then the overall prevalence could well exceed 1 in 3000.

Dystrophin: a clinical perspective

Dystrophin, the protein product of the gene related to Duchenne and Becker muscular dystrophies, is a large cytoskeletal protein associated with the muscle fiber membrane. Recently identified dystrophin-related myopathies affecting animals can serve as experimental models for human disease. Immunologic detection of dystrophin in clinical muscle biopsies provides a direct biochemical test for both Duchenne and Becker muscular dystrophies. Applications of dystrophin testing include improved diagnostic accuracy, carrier detection, fetal diagnosis, and evaluation of asymptomatic male infants identified as a result of neonatal screening for increased serum creatine kinase levels. Identification of dystrophin has brought us to the point of addressing rational therapies.

Screening for Duchenne muscular dystrophy

A programme was introduced in Wales to screen all 18 month old boys who were not yet walking for raised creatine kinase activity within the existing community developmental screening programme. During an 18 month period 25 229 such boys were identified of whom 19 930 (79%) had a Denver developmental screening test and 338 (1.7%) of these were not walking. Two hundred and five of those who did not walk (61%) had creatine kinase activity assayed and two cases of Duchenne muscular dystrophy were detected. We conclude that screening boys of 18 months who do not walk is worthwhile if the opportunity arises, but that a population based screening programme of this type is not justified as detection rates will be unacceptably low.

Early diagnosis and secondary prevention of Duchenne muscular dystrophy

A total of 33 young boys (mean age 3.4 years) with Duchenne muscular dystrophy and 21 normal controls (mean age 3.5 years) were assessed using the Griffiths's mental development scales and the Reynell language scales. The boys with Duchenne muscular dystrophy were significantly developmentally delayed when compared with the control group. The developmental delay was most pronounced in locomotor function and language. There was no significant difference in social class distribution. Early diagnosis of Duchenne muscular dystrophy is of vital importance if secondary cases within families are to be prevented. While diagnosis is still unacceptably late in most cases, it can be improved if all boys with this pattern of developmental delay are screened for Duchenne muscular dystrophy by measurement of creatine kinase activity.

Some studies of the Duchenne and autosomal recessive types of muscular dystrophy

The prevalence of Duchenne muscular dystrophy in the North of England (population 3.07 million) was 4.0 x 10(-5) in 1968, 3.6 x 10(-5) in 1979 and at least 2.3 x 10(-5) in 1988. The incidence in males was 31.2, 22.4 and at least 17.8 x 10(-5) in successive decades since 1952. Thirty-five percent of cases over the last 35 years have been preventable; but recently major additional educational programmes and routine screening tests for presymptomatic cases would have been required to improve prevention. The mortality has not changed in the last 20 years. Previously published criteria for the diagnosis of autosomal recessive muscular dystrophy in childhood have been tested prospectively. Seven new children fitting these criteria and 6 other girls with muscular dystrophy are described. Only 5 appear to have the autosomal recessive disease. Two boys had DNA deletions and 2 girls were severely manifesting carriers of the Duchenne gene.