Reliability of the North Star Ambulatory Assessment in a multicentric setting

[Upper limb functional assessment scale for children with Duchenne muscular dystrophy and Spinal muscular atrophy]

Duchenne muscular dystrophy (DMD) and Spinal muscular atrophy (SMA) causes significant disability and progressive functional impairment. Readily available instruments that assess functionality, especially in advanced stages of the disease, are required to monitor the progress of the disease and the impact of therapeutic interventions.

OBJECTIVE

To describe the development of a scale to evaluate upper limb function (UL) in patients with DMD and SMA, and describe its validation process, which includes self-training for evaluators.

PATIENTS AND METHOD

The development of the scale included a review of published scales, an exploratory application of a pilot scale in healthy children and those with DMD, self-training of evaluators in applying the scale using a handbook and video tutorial, and assessment of a group of children with DMD and SMA using the final scale. Reliability was assessed using Cronbach and Kendall concordance and with intra and inter-rater test-retest, and validity with concordance and factorial analysis.

RESULTS

A high level of reliability was observed, with high internal consistency (Cronbach a = 0.97), and inter-rater (Kendall W = 0.96) and intra-rater concordance (r = 0.97 to 0.99). The validity was demonstrated by the absence of significant differences between results by different evaluators with an expert evaluator (F = 0.023, p > .5), and by the factor analysis that showed that four factors account for 85.44% of total variance.

CONCLUSIONS

This scale is a reliable and valid tool for assessing UL functionality in children with DMD and SMA. It is also easily implementable due to the possibility of self-training and the use of simple and inexpensive materials.

Evaluation of muscular changes by ultrasound Nakagami imaging in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most common debilitating muscular disorder. Developing a noninvasive measure for monitoring the progression of this disease is critical. The present study tested the effectiveness of using ultrasound Nakagami imaging to evaluate the severity of the dystrophic process. A total of 47 participants (40 with DMD and 7 healthy controls) were recruited. Patients were classified into stage 1 (presymptomatic and ambulatory), stage 2 (early nonambulatory), and stage 3 (late nonambulatory). All participants underwent ultrasound examinations on the rectus femoris, tibialis anterior, and gastrocnemius. The results revealed that the ultrasound Nakagami parameter correlated positively with functional severity in the patients with DMD. The median Nakagami parameter of the gastrocnemius muscle increased from 0.50 to 0.85, corresponding to the largest dynamic range between normal and stage 3. The accuracy, sensitivity, and specificity of diagnosing walking function were 85.52%, 76.31%, and 94.73%, respectively. The Nakagami parameter of the rectus femoris and gastrocnemius muscles correlated negatively with the 6-minute walking distance in the ambulatory patients. Therefore, changes in the Nakagami parameter for the gastrocnemius muscle are suitable for monitoring disease progression in ambulatory patients and for predicting ambulation loss. Ultrasound Nakagami imaging shows potential for evaluating patients with DMD.

Neck flexor muscle strength and its relation with functional performance in Duchenne muscular dystrophy

AIM

The aim of this study was to investigate the relationship between neck flexor muscle strength and functional performance in children with DMD.

METHODS

A total of 70 children with DMD between Level 1 and 3 according to Brooke Lower Extremity Functional Classification (BLEFC) were included in the study. Children were divided into 2 groups according to neck flexor strength measured by Medical Research Council Scale as Group 1 (3⁻ and below) and Group 2 (3 and above). Functional performance was assessed by 6 Minute Walk Distance (6MWD) and timed performance tests, and ambulatory status by North Star Ambulatory Assessment (NSAA). Correlations between neck flexor strength and performance tests were analyzed by using Spearman's correlation coefficient in non-parametric conditions.

RESULTS

Thirty-six and 34 children were included in Group 1 and 2, respectively. No statistically significant difference was found in BLEFC between groups (z = -1.225, p > 0.05). 6MWD (z = -2.574, p = 0.01) was found to be longer and NSAA (z = -2.565, p = 0.01) was higher in Group 2. Positive, moderate, statistically significant correlations were determined between neck flexor muscle strength and 6MWD (p < 0.01, r = 0.374); NSAA (p < 0.01, r = 0.399) while a negative, weak correlation between neck flexor muscle strength and the duration for standing from supine position (p = 0.02, r = -0.290).

CONCLUSIONS

The results indicate the relationship of neck flexor muscle strength and functional performance in DMD children. It is thought that the approaches to maintain neck flexor muscle strength from the early stages of disease process may support functional activities of daily life with less compensation and effort in DMD.

Developing standardized corticosteroid treatment for Duchenne muscular dystrophy

Despite corticosteroids being the only treatment documented to improve strength and function in boys with Duchenne muscular dystrophy (DMD) corticosteroid prescription is inconsistent and in some countries, corticosteroids are not prescribed. We are conducting a clinical trial that (1) compares the 3 most frequently prescribed corticosteroid regimes; (2) standardizes treatment of DMD complications; and (3) standardizes prevention of corticosteroid side effects. Investigators at 38 sites in 5 countries plan to recruit 300 boys aged 4-7 who are randomly assigned to one of three regimens: daily prednisone; daily deflazacort; or intermittent prednisone (10days on/10days off). Boys are followed for a minimum of 3years to assess the relative effectiveness and adverse event profiles of the different regimens. The primary outcome is a 3-dimensional variable consisting of log-transformed time to rise from the floor, forced vital capacity, and subject/parent satisfaction with treatment, each averaged over all post-baseline visits. The study protocol includes evidence- and consensus-based treatment of DMD complications and of corticosteroid side effects. This study seeks to establish a standard corticosteroid regimen for DMD. Since all new interventions for DMD are being developed as add-on therapies to corticosteroids, defining the optimum regimen is of importance for all new treatments.

Identification of serum protein biomarkers for utrophin based DMD therapy

Despite promising therapeutic avenues, there is currently no effective treatment for Duchenne muscular dystrophy (DMD), a lethal monogenic disorder caused by the loss of the large cytoskeletal protein, dystrophin. A highly promising approach to therapy, applicable to all DMD patients irrespective to their genetic defect, is to modulate utrophin, a functional paralogue of dystrophin, able to compensate for the primary defects of DMD restoring sarcolemmal stability. One of the major difficulties in assessing the effectiveness of therapeutic strategies is to define appropriate outcome measures. In the present study, we utilised an aptamer based proteomics approach to profile 1,310 proteins in plasma of wild-type, mdx and Fiona (mdx overexpressing utrophin) mice. Comparison of the C57 and mdx sera revealed 83 proteins with statistically significant >2 fold changes in dystrophic serum abundance. A large majority of previously described biomarkers (ANP32B, THBS4, CAMK2A/B/D, CYCS, CAPNI) were normalised towards wild-type levels in Fiona animals. This work also identified potential mdx markers specific to increased utrophin (DUS3, TPI1) and highlights novel mdx biomarkers (GITR, MYBPC1, HSP60, SIRT2, SMAD3, CNTN1). We define a panel of putative protein mdx biomarkers to evaluate utrophin based strategies which may help to accelerate their translation to the clinic.

Revised Hammersmith Scale for spinal muscular atrophy: A SMA specific clinical outcome assessment tool

Recent translational research developments in Spinal Muscular Atrophy (SMA), outcome measure design and demands from regulatory authorities require that clinical outcome assessments are 'fit for purpose'. An international collaboration (SMA REACH UK, Italian SMA Network and PNCRN USA) undertook an iterative process to address discontinuity in the recorded performance of the Hammersmith Functional Motor Scale Expanded and developed a revised functional scale using Rasch analysis, traditional psychometric techniques and the application of clinical sensibility via expert panels. Specifically, we intended to develop a psychometrically and clinically robust functional clinician rated outcome measure to assess physical abilities in weak SMA type 2 through to strong ambulant SMA type 3 patients. The final scale, the Revised Hammersmith Scale (RHS) for SMA, consisting of 36 items and two timed tests, was piloted in 138 patients with type 2 and 3 SMA in an observational cross-sectional multi-centre study across the three national networks. Rasch analysis demonstrated very good fit of all 36 items to the construct of motor performance, good reliability with a high Person Separation Index PSI 0.98, logical and hierarchical scoring in 27/36 items and excellent targeting with minimal ceiling. The RHS differentiated between clinically different groups: SMA type, World Health Organisation (WHO) categories, ambulatory status, and SMA type combined with ambulatory status (all p < 0.001). Construct and concurrent validity was also confirmed with a strong significant positive correlation with the WHO motor milestones rs = 0.860, p < 0.001. We conclude that the RHS is a psychometrically sound and versatile clinical outcome assessment to test the broad range of physical abilities of patients with type 2 and 3 SMA. Further longitudinal testing of the scale with regards change in scores over 6 and 12 months are required prior to its adoption in clinical trials.

Duchenne Regulatory Science Consortium Meeting on Disease Progression Modeling for Duchenne Muscular Dystrophy

INTRODUCTION

The Duchenne Regulatory Science Consortium (D-RSC) was established to develop tools to accelerate drug development for DMD.  The resulting tools are anticipated to meet validity requirements outlined by qualification/endorsement pathways at both the U.S. Food and Drug Administration (FDA) and European Medicines Administration (EMA), and will be made available to the drug development community. The initial goals of the consortium include the development of a disease progression model, with the goal of creating a model that would be used to forecast changes in clinically meaningful endpoints, which would inform clinical trial protocol development and data analysis.  Methods: In April of 2016 the consortium and other experts met to formulate plans for the development of the model.  Conclusions: Here we report the results of the meeting, and discussion as to the form of the model that we plan to move forward to develop, after input from the regulatory authorities.

Quantitative Ultrasound Assessment of Duchenne Muscular Dystrophy Using Edge Detection Analysis

OBJECTIVES

The purpose of this study was to investigate the ability of quantitative ultrasound (US) using edge detection analysis to assess patients with Duchenne muscular dystrophy (DMD).

METHODS

After Institutional Review Board approval, US examinations with fixed technical parameters were performed unilaterally in 6 muscles (biceps, deltoid, wrist flexors, quadriceps, medial gastrocnemius, and tibialis anterior) in 19 boys with DMD and 21 age-matched control participants. The muscles of interest were outlined by a tracing tool, and the upper third of the muscle was used for analysis. Edge detection values for each muscle were quantified by the Canny edge detection algorithm and then normalized to the number of edge pixels in the muscle region. The edge detection values were extracted at multiple sensitivity thresholds (0.01-0.99) to determine the optimal threshold for distinguishing DMD from normal. Area under the receiver operating curve values were generated for each muscle and averaged across the 6 muscles.

RESULTS

The average age in the DMD group was 8.8 years (range, 3.0-14.3 years), and the average age in the control group was 8.7 years (range, 3.4-13.5 years). For edge detection, a Canny threshold of 0.05 provided the best discrimination between DMD and normal (area under the curve, 0.96; 95% confidence interval, 0.84-1.00). According to a Mann-Whitney test, edge detection values were significantly different between DMD and controls (P < .0001).

CONCLUSIONS

Quantitative US imaging using edge detection can distinguish patients with DMD from healthy controls at low Canny thresholds, at which discrimination of small structures is best. Edge detection by itself or in combination with other tests can potentially serve as a useful biomarker of disease progression and effectiveness of therapy in muscle disorders.

Functional changes in Becker muscular dystrophy: implications for clinical trials in dystrophinopathies

We performed a 1-year longitudinal study of Six Minute Walk Test (6MWT), North Star Ambulatory Assessment (NSAA), and timed function tests in Becker muscular dystrophy (BMD). Skeletal muscle dystrophin was quantified by immunoblot. We grouped deletions ending on exon 45 ("del 45-x", n = 28) or 51 ("del x-51", n = 10); isolated exon 48 deletion ("del 48", n = 10); and other mutations (n = 21). Only patients in the "del 45-x" or "other" groups became non-ambulatory (n = 5, log-rank p = n.s.) or unable to run (n = 22, p < 0.001). All measures correlated positively with dystrophin quantity and negatively with age, and were significantly more impaired in the "del 45-x" and "other" groups. After one year, NSAA score decreased significantly (-0.9 ± 1.6, p < 0.001); in the "del 45-x" group, both NSAA (-1.3 ± 1.7, p = 0.001) and 6MWT (-12 ± 31 m, p = 0.059) decreased. We conclude that patients with "del x-51" or "del 48" mutations have mild or asymptomatic BMD, while "del 45-x" mutations cause comparatively severe weakness, and functional deterioration in 1 year. Furthermore, exon 51 skipping could be more effective than exon 45 skipping in Duchenne muscular dystrophy.

Revised North Star Ambulatory Assessment for Young Boys with Duchenne Muscular Dystrophy

The advent of therapeutic approaches for Duchenne muscular dystrophy (DMD) has highlighted the need to identify reliable outcome measures for young boys with DMD. The aim of this study was to develop a revised version of the North Star Ambulatory Assessment (NSAA) suitable for boys between the age of 3 and 5 years by identifying age appropriate items and revising the scoring system accordingly. Using the scale in 171 controls between the age of 2.9 and 4.8 years, we identified items that were appropriate at different age points. An item was defined as age appropriate if it was completed, achieving a full score, by at least 85% of the typically developing boys at that age. At 3 years (±3months) there were only 8 items that were age appropriate, at 3 years and 6 months there were 13 items while by the age of 4 years all 17 items were appropriate. A revised version of the scale was developed with items ordered according to the age when they could be reliably performed. The application of the revised version of the scale to data collected in young DMD boys showed that very few of the DMD boys were able to complete with a full score all the age appropriate items. In conclusion, our study suggests that a revised version of the NSAA can be used in boys from the age of 3 years to obtain information on how young DMD boys acquire new abilities and how this correlates with their peers.

Treatment with L-citrulline and metformin in Duchenne muscular dystrophy: study protocol for a single-centre, randomised, placebo-controlled trial

Background

Duchenne muscular dystrophy (DMD) is an X-linked recessive disease that affects 1 in 3500–6000 male births. Despite broad research aiming to improve muscle function as well as heart and brain function, sufficient therapeutic efficacy has not yet been achieved and current therapeutic management is still supportive. In a recent pilot trial, oral treatment with l-arginine and metformin showed consistent changes of muscular metabolism both in vitro and in vivo by raising NO levels and expression of mitochondrial proteins in the skeletal muscle tissue of patients with DMD. This randomised, double-blind, placebo-controlled trial aims to demonstrate the superiority of l-citrulline and metformin therapy over placebo in DMD patients with regard to the Motor Function Measure (MFM) D1 subscore (primary endpoint) as well as additional clinical and subclinical tests.

Methods/Design

A total of 40–50 ambulant patients with DMD will be recruited at the outpatient department of the University of Basel Children’s Hospital (Switzerland), as well as from the DMD patient registries of Switzerland, Germany and Austria. Patients will be randomly allocated to one of the two arms of the study and will receive either a combination of l-citrulline and metformin or placebo for 26 weeks. Co-medication with glucocorticoids is allowed. The primary endpoint is the change of the MFM D1 subscore from baseline to week 26 under l-citrulline and metformin therapy. Secondary endpoints will include the motor function measure (MFM) and its items and subscores, the 6-minute walking test, timed function tests and quantitative muscle testing. Furthermore, quantitative muscle MRI assessment to evaluate the muscle fat fraction as well as safety and biomarker laboratory analyses from blood will be included. For comparison, muscle metabolism and mitochondrial function will be analysed in 10–20 healthy age-matched male children.

Discussion

The aim of this study is to test if a 6-month treatment of a combination of l-citrulline and metformin is more effective than placebo in preventing loss of motor function and muscle degeneration in DMD. The MFM D1 subscore is used as a clinical outcome measure and a quantitative muscle MRI assessment as the surrogate outcome measure of fatty muscle degeneration.

Trial registration

ClinicalTrials.gov: NCT01995032. Registered on 20 November 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1503-1) contains supplementary material, which is available to authorized users.

Can Quantitative Muscle Strength and Functional Motor Ability Differentiate the Influence of Age and Corticosteroids in Ambulatory Boys with Duchenne Muscular Dystrophy?

BACKGROUND

In the absence of a curative treatment for Duchenne Muscular Dystrophy (DMD), corticosteroid therapy (prednisone, deflazacort) has been adopted as the standard of care, as it slows the progression of muscle weakness and enables longer retention of functional mobility. The ongoing development of novel pharmacological agents that target the genetic defect underlying DMD offer hope for a significant alteration in disease progression; however, substantiation of therapeutic efficacy has proved challenging. Identifying functional outcomes sensitive to the early, subtle changes in muscle function has confounded clinical trials. Additionally, the alterations in disease progression secondary to corticosteroid therapy are not well described making it difficult to ascertain the benefits of novel agents, often taken concurrently with corticosteroids.

OBJECTIVE

The purpose of this study was to examine outcome responsiveness to corticosteroid therapy and age at the onset of a natural history study of ambulatory boys with DMD.

METHODS

Eighty-five ambulatory boys with DMD (mean age 93 mo, range 49 to 180 mo) were recruited into this study. Fifty participants were on corticosteroid therapy, while 33 were corticosteroid naïve at the baseline assessment. Within each treatment group boys were divided in two age groups, 4 to 7 years and 8 and greater years of age. The Biodex System 3 Pro isokinetic dynamometer was used to assess muscle strength. Motor skills were assessed using the upper two dimensions (standing/walking, running & jumping) of the Gross Motor Function Measure (GMFM 88) and Timed Motor Tests (TMTs) (10-meter run, sit to stand, supine to stand, climb 4-stairs). Two way analysis of variance and Pearson correlations were used for analysis.

RESULTS

A main effect for age was seen in select lower extremity muscle groups (hip flexors, knee extensors and ankle dorsiflexors), standing dimension skills, and all TMTs with significantly greater weakness and loss of motor skill ability seen in the older age group regardless of treatment group. Interaction effects were seen for the walking, running, and jumping dimension of the GMFM with the naïve boys scoring higher in the younger group and boys on corticosteroid therapy scoring higher in the older group. The TMT of climb 4-stairs demonstrated a significant treatment effect with the boys on corticosteroid therapy climbing stairs faster than those who were naïve, regardless of age. Examination of individual items within the upper level GMFM dimensions revealed select motor skills are more informative of disease progression than others; indicating their potential to be sensitive indicators of alterations in disease progression and intervention efficacy. Analysis of the relationship between muscle group strength and motor skill performance revealed differences in use patterns in the corticosteroid versus naïve boys.

CONCLUSION

Significant muscle weakness is apparent in young boys with DMD regardless of corticosteroid treatment; however, older boys on corticosteroid therapy tend to have greater retention of muscle strength and motor skill ability than those who are naive. Quantification of muscle strength via isokinetic dynamometry is feasible and sensitive to the variable rates of disease progression in lower extremity muscle groups, but possibly most informative are the subtle changes in the performance characteristics of select motor skills. Further analysis of longitudinal data from this study will explore the influence of corticosteroid therapy on muscle strength and further clarify its impact on motor performance.

The 6-minute walk test, motor function measure and quantitative thigh muscle MRI in Becker muscular dystrophy: A cross-sectional study

Becker muscular dystrophy (BMD) has an incidence of 1 in 16 000 male births. This cross-sectional study investigated the relation between validated functional scores and quantitative MRI (qMRI) of thigh muscles in 20 ambulatory BMD patients, aged 18.3-60 years (mean 31.2; SD 11.1). Clinical assessments included the motor function measure (MFM) and its subscales, as well as timed function tests such as the 6-minute walk test (6MWT) and the timed 10-m run/walk test. Quantitative MRI of the thigh muscles included the mean fat fraction (MFF) using a 2-point Dixon (2-PD) technique, and transverse relaxation time (T2) measurements. The mean MFM value was 80.4%, SD 9.44 and the D1 subscore 54.5%, SD 19.9. The median 6MWT was 195m, IQR 160-330.2. The median 10-m run/walk test was 7.4 seconds, IQR 6.1-9.3. The mean fat fraction of the thigh muscles was 55.6%, SD 17.4%, mean T2 relaxation times of all muscles: 69.9 ms, SD 14.4. The flexors had the highest MFF and T2 relaxation times, followed by the extensors and the adductors. MFF and global T2 relaxation times were highly negatively correlated with the MFM total, D1-subscore and 6MWT, and positively correlated with the 10 m run/walk test time (p < 0.01). Age was not correlated with MFF, global T2 relaxation time or clinical assessments. Both MFF and T2 measures in the thigh muscle were well correlated with clinical function in BMD and may serve as a surrogate outcome measure in clinical trials.

Clinical utility of serum biomarkers in Duchenne muscular dystrophy

Assessments of disease progression and response to therapies in Duchenne muscular dystrophy (DMD) patients remain challenging. Current DMD patient assessments include complex physical tests and invasive procedures such as muscle biopsies, which are not suitable for young children. Defining alternative, less invasive and objective outcome measures to assess disease progression and response to therapy will aid drug development and clinical trials in DMD. In this review we highlight advances in development of non-invasive blood circulating biomarkers as a means to assess disease progression and response to therapies in DMD.

Constipation in Duchenne Muscular Dystrophy: Prevalence, Diagnosis, and Treatment

OBJECTIVES

To determine the prevalence and clinical characteristics of constipation among patients with Duchenne muscular dystrophy (DMD).

STUDY DESIGN

This cross-sectional prospective study included 120 patients (age range 5-30 years old) with an established diagnosis of DMD. Participants filled out the constipation section of a validated Questionnaire on Pediatric Gastrointestinal Symptoms based on Rome-III Criteria (QPGS-RIII) for the diagnosis of functional constipation as part of a routine clinic visit. We evaluated several potential screening methods for constipation: the Bristol stool form scale, routine physical examination, and fecal load on abdominal radiograph. These methods were compared with the QPGS-RIII in diagnosing functional constipation. Risk factors for the development of functional constipation were determined.

RESULTS

Based on the QPGS-RIII, 46.7% of patients with DMD in this cohort were diagnosed with functional constipation. Prevalence was not affected by age or functional status. None of the screening methods tested were sensitive enough to diagnose functional constipation. Among patients with constipation, only 43.6% received specific treatment for constipation and only one-half of these treated patients reported resolution of constipation.

CONCLUSIONS

This study systematically examined constipation among patients with DMD and provides evidence that constipation among patients with DMD is highly prevalent, underdiagnosed, and undertreated. QPGS-RIII is easy to administer and is an efficient tool to diagnose functional constipation in patients with DMD in a clinic setting.

Health-related quality of life and functional changes in DMD: A 12-month longitudinal cohort study

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At baseline, the PedsQL^TM inventories correlated with almost all the functional measures.

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There was a significant decrease between baseline and 12 months on PedsQL^TM GCS.

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This decrement paralleled with the decrement in the functional outcome measures.

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PedsQL^TM correlates with the level of impairment.

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This correlations were not confirmed when 12 month changes are considered.

In Duchenne muscular dystrophy (DMD) little has been reported on the association between clinical outcome measures and patient health-related quality of life (HRQOL) tools. Our study evaluated the relationship between 12 month changes on the Generic Core Scales (GCS), the Multidimensional Fatigue Scale and the Neuromuscular Module of the PedsQL^TM with several outcome measures (6 minute walk test, North Star Ambulatory Assessment and timed items) in ambulatory DMD. Ninety-eight ambulatory DMD in a multicentric setting were included in the study. At baseline, the PedsQL^TM inventories correlated with almost all the functional measures On the Child Self-Report there was a significant decrease between baseline and 12 months on the PedsQL^TM GCS and its first domain, in parallel with the decrement in the functional outcome measures. Correlation between the 12 month changes on the PedsQL^TM inventories and functional measures were almost all negligible. Similar results were obtained on the Parent Proxy-Report.

In conclusion, PedsQL^TM correlates with the level of impairment at baseline, but this does not hold true when 12 month changes are considered. Further studies comparing different tools are needed to better elucidate the complexity of the relationship between HRQOL and functional performances.

The NorthStar Ambulatory Assessment in Duchenne muscular dystrophy: considerations for the design of clinical trials

OBJECTIVE

With the emergence of experimental therapies for Duchenne muscular dystrophy (DMD), it is fundamental to understand the natural history of this disorder to properly design clinical trials. The aims of this study were to assess the effects produced on motor function by different DMD genotypes and early initiation of glucocorticoids.

METHODS

Through the NorthStar Network, standardised clinical data including the NorthStar Ambulatory Assessment score (NSAA) on 513 ambulant UK boys with DMD were analysed from 2004 to 2012. For the analysis of the genetic subpopulation, we also included data from 172 Italian boys with DMD. NSAA raw scores were converted into linear scores.

RESULTS

On the linearised NSAA, we observed an average decline of 8 units/year (4 units on raw NSAA analysis) after age 7. The median age at loss of ambulation (LOA) was 13 years (95% CI 12.1 to 13.5); 2 years prior to LOA, the estimated mean linearised NSAA score was 42/100 (13/34 raw scale). Starting glucocorticoids between 3 and 5 years conferred an additional gain in motor function of 3 units/year (1.3 raw units) up to age 7. When analysing the effect of genotype in the UK and Italian cumulative cohorts, individuals with deletions amenable to exons 44 and 46 skipping declined at a slower rate over 2 years (9 units (4 raw units), p<0.001), while 53 and 51 skippable deletions showed a faster decline of 14 (4.5; p<0.001) and 5 linearised units (2.4 NSAA units; p=0.02), respectively.

CONCLUSIONS

Our study provides a novel insight on the current natural history of DMD, which will be instrumental for the design of future clinical trials.

Where do we stand in trial readiness for autosomal recessive limb girdle muscular dystrophies?

Autosomal recessive limb girdle muscular dystrophies (LGMD2) are a group of genetically heterogeneous diseases that are typically characterised by progressive weakness and wasting of the shoulder and pelvic girdle muscles. Many of the more than 20 different conditions show overlapping clinical features with other forms of muscular dystrophy, congenital, myofibrillar or even distal myopathies and also with acquired muscle diseases. Although individually extremely rare, all types of LGMD2 together form an important differential diagnostic group among neuromuscular diseases. Despite improved diagnostics and pathomechanistic insight, a curative therapy is currently lacking for any of these diseases. Medical care consists of the symptomatic treatment of complications, aiming to improve life expectancy and quality of life. Besides well characterised pre-clinical tools like animal models and cell culture assays, the determinants of successful drug development programmes for rare diseases include a good understanding of the phenotype and natural history of the disease, the existence of clinically relevant outcome measures, guidance on care standards, up to date patient registries, and, ideally, biomarkers that can help assess disease severity or drug response. Strong patient organisations driving research and successful partnerships between academia, advocacy, industry and regulatory authorities can also help accelerate the elaboration of clinical trials. All these determinants constitute aspects of translational research efforts and influence patient access to therapies. Here we review the current status of determinants of successful drug development programmes for LGMD2, and the challenges of translating promising therapeutic strategies into effective and accessible treatments for patients.

Composite biomarkers for assessing Duchenne muscular dystrophy: an initial assessment

BACKGROUND

Compared with individual parameters, composite biomarkers may provide a more effective means for monitoring disease progression and the effects of therapy in clinical trials than single measures. In this study, we built composite biomarkers for use in Duchenne muscular dystrophy by combining values from two objective measures of disease severity: electrical impedance myography and quantitative ultrasound and evaluating how well they correlated to standard functional measures.

METHODS

Using data from an ongoing study of electrical impedance myography and quantitative ultrasound in 31 Duchenne muscular dystrophy and 26 healthy boys aged 2-14 years, we combined data sets by first creating z scores based on the normal subject data and then using simple mathematical operations (addition and multiplication) to create composite measures. These composite scores were then correlated to age and standard measures of function including the 6-minute walk test, the North Star Ambulatory Assessment, and handheld dynamometry.

RESULTS

Combining data sets resulted in stronger correlations with all four outcomes than for either electrical impedance myography or quantitative ultrasound alone in six of eight instances. These improvements reached statistical significance (P < 0.05) in several cases. For example, the correlation coefficient for the composite measure with the North Star Ambulatory Assessment was 0.79 but was only 0.66 and 0.67 (respectively) for gray scale level and electrical impedance myography separately.

CONCLUSIONS

Arithmetically derived composite scores can provide stronger correlations to functional measures than isolated biomarkers. Longitudinal study of such composite markers in Duchenne muscular dystrophy clinical trials is warranted.

Quantitative muscle ultrasound in Duchenne muscular dystrophy: a comparison of techniques

INTRODUCTION

Muscle pathology in Duchenne muscular dystrophy (DMD) can be quantified using ultrasound by measuring either the amplitudes of sound-waves scattered back from the tissue [quantitative backscatter analysis (QBA)] or by measuring these backscattered amplitudes after compression into grayscale levels (GSL) obtained from the images.

METHODS

We measured and compared QBA and GSL from 6 muscles of 25 boys with DMD and 25 healthy subjects, aged 2-14 years, with age and, in DMD, with function (North Star Ambulatory Assessment).

RESULTS

Both QBA and GSL were measured reliably (intraclass correlation ≥ 0.87) and were higher in DMD than controls (P < 0.0001). In DMD, average QBA and GSL measured from superficial regions of muscle increased (rho ≥ 0.47, P < 0.05) with both higher age and worse function; in contrast, GSL measured from whole regions of muscle did not.

CONCLUSIONS

QBA and GSL measured from superficial regions of muscle can similarly quantify muscle pathology in DMD.

Development and Reliability of the Functional Evaluation Scale for Duchenne Muscular Dystrophy, Gait Domain: A Pilot Study

BACKGROUND AND PURPOSE

The progression of Duchenne muscular dystrophy (DMD) results in the emergence of multiple and varied synergies to compensate muscle weakness and to deal with the demands of the functional tasks (e.g. gait). No functional evaluation instrument for individuals with DMD allows the detailed description (subjective qualitative evaluation) and compensatory movement scoring (objective quantitative evaluation) exclusively of gait. For this reason, clinicians and therapists face difficulties in assessment and decision-making of this functional activity. This study aimed to elaborate the gait domain of the Functional Evaluation Scale for DMD (FES-DMD-GD) and test its intra-rater and inter-rater reliabilities and its relationship with age and timed motor performance.

METHOD

We listed all the compensatory movements observed in 102 10-m gait videos of 51 children with DMD. Based on this report, the FES-DMD-GD was created and submitted to the review of 10 experts. After incorporating the experts suggestions, three examiners scored the videos using the FES-DMD-GD. The intra-rater and inter-rater reliabilities was calculated. Spearman correlation tests investigated the relationships between FES-DMD-GD and age and timed motor performance (p < 0.05).

RESULTS

The FES-DMD-GD was composed of three phases and had 14 items to quantify compensatory movements on gait. Intra-class correlation coefficients ranged from acceptable (0.74) to excellent (0.99). FES-DMD-GD correlated to age and timed motor performance.

CONCLUSION

This pilot version of FES-DMD-GD showed reliability and correlated to age and timed motor performance.

The 6 minute walk test and performance of upper limb in ambulant duchenne muscular dystrophy boys

The Performance of Upper Limb (PUL) test was specifically developed for the assessment of upper limbs in Duchenne muscular dystrophy (DMD). The first published data have shown that early signs of involvement can also be found in ambulant DMD boys. The aim of this longitudinal Italian multicentric study was to evaluate the correlation between the 6 Minute Walk Test (6MWT) and the PUL in ambulant DMD boys. Both 6MWT and PUL were administered to 164 ambulant DMD boys of age between 5.0 and 16.17 years (mean 8.82). The 6 minute walk distance (6MWD) ranged between 118 and 557 (mean: 376.38, SD: 90.59). The PUL total scores ranged between 52 and 74 (mean: 70.74, SD: 4.66). The correlation between the two measures was 0.499. The scores on the PUL largely reflect the overall impairment observed on the 6MWT but the correlation was not linear. The use of the PUL appeared to be less relevant in the very strong patients with 6MWD above 400 meters, who, with few exceptions had near full scores. In patients with lower 6MWD the severity of upper limb involvement was more variable and could not always be predicted by the 6MWD value or by the use of steroids. Our results confirm that upper limb involvement can already be found in DMD boys even in the ambulant phase.

Suitability of North Star Ambulatory Assessment in young boys with Duchenne muscular dystrophy

The aim of this study was to establish the suitability of the North Star Ambulatory Assessment for use in young boys with Duchenne muscular dystrophy. We studied 147 typically developing and 144 boys affected by Duchenne muscular dystrophy between the ages of 3 and 5 years. More than 85% of the typically developing boys by the age of 4 years had full scores on all the items with total scores ≥33/34. Before the age of 4 years more than 15% of the typically developing boys did not achieve full scores on all the items. Some items, such as standing on one leg, showed significant improvement with age. In contrast, other activities were rarely achieved even in the older boys. Even if there was a progressive increase in scores with age, both total and individual item scores in Duchenne were still far from those obtained in the typically developing children of the same age. Our findings suggest that the North Star Ambulatory Assessment can be reliably used at least from the age of 4 years. Longitudinal natural history data studies are needed to assess possible changes over time and the possible effect of early steroids.

Long term natural history data in ambulant boys with Duchenne muscular dystrophy: 36-month changes

The 6 minute walk test has been recently chosen as the primary outcome measure in international multicenter clinical trials in Duchenne muscular dystrophy ambulant patients. The aim of the study was to assess the spectrum of changes at 3 years in the individual measures, their correlation with steroid treatment, age and 6 minute walk test values at baseline. Ninety-six patients from 11 centers were assessed at baseline and 12, 24 and 36 months after baseline using the 6 minute walk test and the North Star Ambulatory Assessment. Three boys (3%) lost the ability to perform the 6 minute walk test within 12 months, another 13 between 12 and 24 months (14%) and 11 between 24 and 36 months (12%). The 6 minute walk test showed an average overall decline of -15.8 (SD 77.3) m at 12 months, of -58.9 (SD 125.7) m at 24 months and -104.22 (SD 146.2) m at 36 months. The changes were significantly different in the two baseline age groups and according to the baseline 6 minute walk test values (below and above 350 m) (p<0.001). The changes were also significantly different according to steroid treatment (p = 0.01). Similar findings were found for the North Star Ambulatory Assessment. These are the first 36 month longitudinal data using the 6 minute walk test and North Star Ambulatory Assessment in Duchenne muscular dystrophy. Our findings will help not only to have a better idea of the progression of the disorder but also provide reference data that can be used to compare with the results of the long term extension studies that are becoming available.

Magnetic resonance imaging and spectroscopy assessment of lower extremity skeletal muscles in boys with Duchenne muscular dystrophy: a multicenter cross sectional study

Introduction

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder that results in functional deficits. However, these functional declines are often not able to be quantified in clinical trials for DMD until after age 7. In this study, we hypothesized that ¹H₂O T₂ derived using ¹H-MRS and MRI-T₂ will be sensitive to muscle involvement at a young age (5–7 years) consistent with increased inflammation and muscle damage in a large cohort of DMD subjects compared to controls.

Methods

MR data were acquired from 123 boys with DMD (ages 5–14 years; mean 8.6 SD 2.2 years) and 31 healthy controls (age 9.7 SD 2.3 years) using 3-Tesla MRI instruments at three institutions (University of Florida, Oregon Health & Science University, and Children’s Hospital of Philadelphia). T₂-weighted multi-slice spin echo (SE) axial images and single voxel ¹H-MRS were acquired from the lower leg and thigh to measure lipid fraction and ¹H₂O T₂.

Results

MRI-T₂, ¹H₂O T₂, and lipid fraction were greater (p<0.05) in DMD compared to controls. In the youngest age group, DMD values were different (p<0.05) than controls for the soleus MRI-T₂, ¹H₂O T₂ and lipid fraction and vastus lateralis MRI-T₂ and ¹H₂O T₂. In the boys with DMD, MRI-T₂ and lipid fraction were greater (p<0.05) in the oldest age group (11–14 years) than the youngest age group (5–6.9 years), while ¹H₂O T₂ was lower in the oldest age group compared to the young age group.

Discussion

Overall, MR measures of T₂ and lipid fraction revealed differences between DMD and Controls. Furthermore, MRI-T₂ was greater in the older age group compared to the young age group, which was associated with higher lipid fractions. Overall, MR measures of T₂ and lipid fraction show excellent sensitivity to DMD disease pathologies and potential therapeutic interventions in DMD, even in the younger boys.

Safety and efficacy of drisapersen for the treatment of Duchenne muscular dystrophy (DEMAND II): an exploratory, randomised, placebo-controlled phase 2 study

BACKGROUND

Duchenne muscular dystrophy is caused by dystrophin deficiency and muscle deterioration and preferentially affects boys. Antisense-oligonucleotide-induced exon skipping allows synthesis of partially functional dystrophin. We investigated the efficacy and safety of drisapersen, a 2'-O-methyl-phosphorothioate antisense oligonucleotide, given for 48 weeks.

METHODS

In this exploratory, double-blind, placebo-controlled study we recruited male patients (≥5 years of age; time to rise from floor ≤7 s) with Duchenne muscular dystrophy from 13 specialist centres in nine countries between Sept 1, 2010, and Sept 12, 2012. By use of a computer-generated randomisation sequence, we randomly allocated patients (2:2:1:1; block size of six; no stratification) to drisapersen 6 mg/kg or placebo, each given subcutaneously and either continuously (once weekly) or intermittently (nine doses over 10 weeks). The primary endpoint was change in 6-min walk distance (6MWD) at week 25 in patients in the intention-to-treat population for whom data were available. Safety assessments included renal, hepatic, and haematological monitoring and recording of adverse events. This trial is registered with ClinicalTrials.gov, number NCT01153932.

FINDINGS

We recruited 53 patients: 18 were given continuous drisapersen, 17 were given intermittent drisapersen, and 18 were given placebo (continuous and intermittent groups combined). At week 25, mean 6MWD had increased by 31·5 m (SE 9·8) from baseline for continuous drisapersen, with a mean difference in change from baseline of 35·09 m (95% CI 7·59 to 62·60; p=0·014) versus placebo. We recorded no difference in 6MWD changes from baseline between intermittent drisapersen (mean change -0·1 [SE 10·3]) and placebo (mean difference 3·51 m [-24·34 to 31·35]) at week 25. The most common adverse events in drisapersen-treated patients were injection-site reactions (14 patients given continuous drisapersen, 15 patients given intermittent drisapersen, and six given placebo) and renal events (13 for continuous drisapersen, 12 for intermittent drisapersen, and seven for placebo), most of which were subclinical proteinuria. None of the serious adverse events reported (one for continuous, two for intermittent, and two for placebo) resulted in withdrawal from the study.

INTERPRETATION

Continuous drisapersen resulted in some benefit in 6MWD versus placebo at week 25. The safety findings are similar to those from previous studies. Ambulation improvements in this young population with early-stage Duchenne muscular dystrophy are encouraging but need to be confirmed in larger studies.

FUNDING

GlaxoSmithKline, Prosensa Therapeutics BV (a subsidiary of Prosensa Holding NV).

Measurement properties of gait-related outcomes in youth with neuromuscular diagnoses: a systematic review

BACKGROUND

Sound measurement properties of outcome tools are essential when evaluating outcomes of an intervention, in clinical practice and in research.

PURPOSE

The purpose of this study was to review the evidence on reliability, measurement error, and responsiveness of measures of gait function in children with neuromuscular diagnoses.

DATA SOURCES

The MEDLINE, CINAHL, EMBASE, and PsycINFO databases were searched up to June 15, 2012.

STUDY SELECTION

Studies evaluating reliability, measurement error, or responsiveness of measures of gait function in 1- to 18-year-old children and youth with neuromuscular diagnoses were included.

DATA EXTRACTION

Quality of the studies was independently rated by 2 raters using a modified COnsensus-based Standards for the selection of health status Measurement INstruments (COSMIN) checklist. Studies with a fair quality rating or better were considered for best evidence synthesis.

DATA SYNTHESIS

Regarding the methodological quality, 32 out of 35 reliability studies, all of the 13 measurement error studies, and 5 out of 10 responsiveness studies were of fair or good quality. Best evidence synthesis revealed moderate to strong evidence for reliability for several measures in children and youth with cerebral palsy (CP) but was limited or unknown in other diagnoses. The Functional Mobility Scale (FMS) and the Gross Motor Function Measure (GMFM) dimension E showed limited positive evidence for responsiveness in children with CP, but it was unknown or controversial in other diagnoses. No information was reported on the minimal important change; thus, evidence on measurement error remained undetermined.

LIMITATIONS

As studies on validity were not included in the review, a comprehensive appraisal of the best available gait-related outcome measure per diagnosis is not possible.

CONCLUSIONS

There is moderate to strong evidence on reliability for several measures of gait function in children and youth with CP, whereas evidence on responsiveness exists only for the FMS and the GMFM dimension E.

Circulating Muscle-specific miRNAs in Duchenne Muscular Dystrophy Patients

Noninvasive biomarkers with diagnostic value and prognostic applications have long been desired to replace muscle biopsy for Duchenne muscular dystrophy (DMD) patients. Growing evidence indicates that circulating microRNAs are biomarkers to assess pathophysiological status. Here, we show that the serum levels of six muscle-specific miRNAs (miR-1/206/133/499/208a/208b, also known as myomiRs) were all elevated in DMD patients (P < 0.01). The receiver operating characteristic curves of circulating miR-206, miR-499, miR-208b, and miR-133 levels reflected strong separation between Becker's muscular dystrophy (BMD) and DMD patients (P < 0.05). miR-206, miR-499, and miR-208b levels were positively correlated with both age and type IIc muscle fiber content in DMD patients (2–6 years), indicating that they might represent the stage of disease as well as the process of regeneration. miR-499 and miR-208b levels were correlated with slow and fast fiber content and might reflect the ratio of slow to fast fibers in DMD patient (>6 years). Fibroblast growth factor, transforming growth factor-β, and tumor necrosis factor-α could affect the secretion of myomiRs, suggesting that circulating myomiRs might reflect the effects of cytokines and growth factors on degenerating and regenerating muscles. Collectively, our data indicated that circulating myomiRs could serve as promising biomarkers for DMD diagnosis and disease progression.

Discovery of serum protein biomarkers in the mdx mouse model and cross-species comparison to Duchenne muscular dystrophy patients

It is expected that serum protein biomarkers in Duchenne muscular dystrophy (DMD) will reflect disease pathogenesis, progression and aid future therapy developments. Here, we describe use of quantitative in vivo stable isotope labeling in mammals to accurately compare serum proteomes of wild-type and dystrophin-deficient mdx mice. Biomarkers identified in serum from two independent dystrophin-deficient mouse models (mdx-Δ52 and mdx-23) were concordant with those identified in sera samples of DMD patients. Of the 355 mouse sera proteins, 23 were significantly elevated and 4 significantly lower in mdx relative to wild-type mice (P-value < 0.001). Elevated proteins were mostly of muscle origin: including myofibrillar proteins (titin, myosin light chain 1/3, myomesin 3 and filamin-C), glycolytic enzymes (aldolase, phosphoglycerate mutase 2, beta enolase and glycogen phosphorylase), transport proteins (fatty acid-binding protein, myoglobin and somatic cytochrome-C) and others (creatine kinase M, malate dehydrogenase cytosolic, fibrinogen and parvalbumin). Decreased proteins, mostly of extracellular origin, included adiponectin, lumican, plasminogen and leukemia inhibitory factor receptor. Analysis of sera from 1 week to 7 months old mdx mice revealed age-dependent changes in the level of these biomarkers with most biomarkers acutely elevated at 3 weeks of age. Serum analysis of DMD patients, with ages ranging from 4 to 15 years old, confirmed elevation of 20 of the murine biomarkers in DMD, with similar age-related changes. This study provides a panel of biomarkers that reflect muscle activity and pathogenesis and should prove valuable tool to complement natural history studies and to monitor treatment efficacy in future clinical trials.

Cross-sectional evaluation of electrical impedance myography and quantitative ultrasound for the assessment of Duchenne muscular dystrophy in a clinical trial setting

BACKGROUND

Electrical impedance myography and quantitative ultrasound are two noninvasive, painless, and effort-independent approaches for assessing neuromuscular disease. Both techniques have potential to serve as useful biomarkers in clinical trials in Duchenne muscular dystrophy. However, their comparative sensitivity to disease status and how they relate to one another are unknown.

METHODS

We performed a cross-sectional analysis of electrical impedance myography and quantitative ultrasound in 24 healthy boys and 24 with Duchenne muscular dystrophy, aged 2 to 14 years with trained research assistants performing all measurements. Three upper and three lower extremity muscles were studied unilaterally in each child, and the data averaged for each individual.

RESULTS

Both electrical impedance myography and quantitative ultrasound differentiated healthy boys from those with Duchenne muscular dystrophy (P < 0.001 for both). Quantitative ultrasound values correlated with age in Duchenne muscular dystrophy boys (rho = 0.45; P = 0.029), whereas electrical impedance myography did not (rho = -0.31; P = 0.14). However, electrical impedance myography phase correlated with age in healthy boys (rho = 0.51; P = 0.012), whereas quantitative ultrasound did not (rho = -0.021; P = 0.92). In Duchenne muscular dystrophy boys, electrical impedance myography phase correlated with the North Star Ambulatory Assessment (rho = 0.65; P = 0.022); quantitative ultrasound revealed a near-significant association (rho = -0.56; P = 0.060). The two technologies trended toward a moderate correlation with one another in the Duchenne muscular dystrophy cohort but not in the healthy group (rho = -0.40; P = 0.054 and rho = -0.32; P = 0.13, respectively).

CONCLUSIONS

Electrical impedance myography and quantitative ultrasound are complementary modalities for the assessment of boys with Duchenne muscular dystrophy; further study and application of these two modalities alone or in combination in a longitudinal fashion are warranted.

Vibration therapy tolerated in children with Duchenne muscular dystrophy: a pilot study

BACKGROUND

Duchenne muscular dystrophy is an X-linked recessive muscular dystrophy. Clinical management primarily involves rehabilitation strategies aimed at preserving functional mobility as long as possible. Side-alternating vibration therapy is a rehabilitation intervention that has shown promise in a number of different neuromuscular disorders, and has the potential to preserve strength, functional mobility, and bone mass. There has been little research regarding the tolerance to side-alternating vibration therapy in muscle diseases such as Duchenne muscular dystrophy.

METHODS

Four patients were recruited for a pilot study assessing the safety and tolerance of side-alternating vibration therapy in individuals with Duchenne muscular dystrophy. All patients participated in a 4-week training period involving side-alternating vibration therapy sessions three times per week. Serum creatine kinase was measured, and adverse effects reviewed at each session with functional mobility assessed before and after the training period.

RESULTS

All patients tolerated the training protocol well, and there were no major changes in functional mobility. One patient had a transient increase in creatine kinase during the study; however, levels of this enzyme were stable overall when comparing the pretraining and posttraining values. Some patients reported subjective improvement during the training period.

CONCLUSIONS

Side-alternating vibration therapy is well tolerated in children with Duchenne muscular dystrophy and may have potential to improve or maintain functional mobility and strength in these patients.

The reliability of the Leeds Movement Performance Index (LMPI): a new tool for neurological physiotherapy

BACKGROUND

Measuring movement performance in people with neurological damage requires a tool that reflects physiotherapy assessment and clinical reasoning. The Leeds Movement Performance Index (LMPI) was previously developed by a group of neurological physiotherapists to fulfill these requirements.

OBJECTIVE

To assess the reliability of the LMPI for use in neurological physiotherapy practice.

METHODS

Twelve senior neurological physiotherapists were trained to use the LMPI and then asked to measure the movement performance of five patients whose movement had been previously video-recorded for this purpose. A retest session was completed after two weeks. Data were analysed to establish internal and external reliability.

RESULTS

Internal reliability was assessed using Cronbach's alpha coefficient, applied to the entire scale (0.862) and to each item (range 0.795-0.892). External (inter-rater) reliability was assessed by a calculation of the intraclass correlation coefficient for scores awarded by multiple raters (0.959), with individual item reliability ranging from 0.874 to 0.968. External (test-retest) reliability was assessed by calculating the Spearman's rank correlation coefficient between scores obtained on two testing occasions (0.792) with values of individual items ranging from 0.397 to 0.674. A variance components analysis partitioned variance into components arising from between-patient variability (55.2%) between-therapist variability (7.8%) and between-testing variability (2.8%).

CONCLUSIONS

RESULTS indicate that the LMPI is a reliable measurement tool when used by senior neurological physiotherapists.

Rasch analysis of clinical outcome measures in spinal muscular atrophy

INTRODUCTION

Trial design for SMA depends on meaningful rating scales to assess outcomes. In this study Rasch methodology was applied to 9 motor scales in spinal muscular atrophy (SMA).

METHODS

Data from all 3 SMA types were provided by research groups for 9 commonly used scales. Rasch methodology assessed the ordering of response option thresholds, tests of fit, spread of item locations, residual correlations, and person separation index.

RESULTS

Each scale had good reliability. However, several issues impacting scale validity were identified, including the extent that items defined clinically meaningful constructs and how well each scale measured performance across the SMA spectrum.

CONCLUSIONS

The sensitivity and potential utility of each SMA scale as outcome measures for trials could be improved by establishing clear definitions of what is measured, reconsidering items that misfit and items whose response categories have reversed thresholds, and adding new items at the extremes of scale ranges.

Detecting meaningful change using the North Star Ambulatory Assessment in Duchenne muscular dystrophy

AIM

Clinician-reported outcome instruments such as the North Star Ambulatory Assessment (NSAA) need to be able to detect clinically important change to be suitable for clinical trials. However, in Duchenne muscular dystrophy (DMD), identifying changes in function is not straightforward. In this study, we use Rasch-transformed data to examine the responsiveness and minimal important difference (MID) of the NSAA in males with DMD receiving different corticosteroid regimes.

METHOD

NSAA data were examined from 198 males (mean age at assessment was 8 y 6 mo [SD 2 y 6 mo] range 4 y-18 y; 805 assessments). Responsiveness was assessed using mean score changes (using Rasch-transformed data) between adjacent pairs of age groups, pairwise squared t-values from paired samples t-tests, and an effect size calculation. The MID was assessed using the effect size calculation and 0.5 standard deviation (SD) of mean score differences.

RESULTS

Our findings revealed a difference in change scores over time between the two corticosteroid regimes. Mean NSAA person estimates were higher in the daily prednisolone group. The mean MID (0.5 SD) was 8.8 and 6.9 for the daily group and intermittent group respectively.

INTERPRETATION

This study, based on Rasch-transformed NSAA data, provides an initial basis for the interpretation of clinical change in DMD over time and between corticosteroid regimes. Our proposed MIDs can be mapped back to differences in specific item content across the range of the NSAA.

Development of the Performance of the Upper Limb module for Duchenne muscular dystrophy

AIM

An international Clinical Outcomes Group consisting of clinicians, scientists, patient advocacy groups, and industries identified a need for a scale to measure motor performance of the upper limb. We report the steps leading to the development of the Performance of the Upper Limb (PUL), a tool specifically designed for assessing upper limb function in ambulant and non-ambulant patients with Duchenne muscular dystrophy (DMD).

METHOD

The development of the PUL followed a number of steps, from the systematic review and a preliminary study exploring the suitability of the existing measures, to the application of a pilot version in a multicentric setting, with Rasch analysis of the preliminary results, leading to a revised pro forma.

RESULTS

The PUL was specifically designed for DMD, with a conceptual framework reflecting the progression of weakness and natural history of functional decline in DMD. Modern psychometric methods were used to create a scale with robust internal reliability, validity, and hierarchical scalability; males with DMD and their families were involved iteratively throughout the process of the clinician-reported outcome assessment tool development to establish clinical meaningfulness and relevance of individual PUL items to activities of daily living.

INTERPRETATION

The module was developed using innovative approaches and will be useful for designing clinical trials.

Quantitative muscle MRI as an assessment tool for monitoring disease progression in LGMD2I: a multicentre longitudinal study

BACKGROUND

Outcome measures for clinical trials in neuromuscular diseases are typically based on physical assessments which are dependent on patient effort, combine the effort of different muscle groups, and may not be sensitive to progression over short trial periods in slow-progressing diseases. We hypothesised that quantitative fat imaging by MRI (Dixon technique) could provide more discriminating quantitative, patient-independent measurements of the progress of muscle fat replacement within individual muscle groups.

OBJECTIVE

To determine whether quantitative fat imaging could measure disease progression in a cohort of limb-girdle muscular dystrophy 2I (LGMD2I) patients over a 12 month period.

METHODS

32 adult patients (17 male;15 female) from 4 European tertiary referral centres with the homozygous c.826C>A mutation in the fukutin-related protein gene (FKRP) completed baseline and follow up measurements 12 months later. Quantitative fat imaging was performed and muscle fat fraction change was compared with (i) muscle strength and function assessed using standardized physical tests and (ii) standard T1-weighted MRI graded on a 6 point scale.

RESULTS

There was a significant increase in muscle fat fraction in 9 of the 14 muscles analyzed using the quantitative MRI technique from baseline to 12 months follow up. Changes were not seen in the conventional longitudinal physical assessments or in qualitative scoring of the T₁w images.

CONCLUSIONS

Quantitative muscle MRI, using the Dixon technique, could be used as an important longitudinal outcome measure to assess muscle pathology and monitor therapeutic efficacy in patients with LGMD2I.

The 6-Minute Walk Test and Person-Reported Outcomes in Boys with Duchenne Muscular Dystrophy and Typically Developing Controls: Longitudinal Comparisons and Clinically-Meaningful Changes Over One Year

Introduction: Data is currently lacking anchoring a 30-meter longitudinal change in walking ability by 6-minute walk test (6MWT) in Duchenne muscular dystrophy as a minimal clinically important difference and “clinically meaningful” person-reported outcomes (PROs) at differing levels of ambulatory ability. Methods: We describe correlation between measures, 1-year change in measures, and correlation of 1-year changes between measures for the six-minute walk test (6MWT), 10-meter run/walk velocity, PedsQL and POSNA Pediatric Outcomes Data Collection Instrument (PODCI) in 24 4-12 year old. ambulatory DMD and 36 typical controls, and determine if minimal clinically important differences (MCID) of PROs contribute to different estimates of 6-minute walk distance (6MWD) change at differing levels of ability. Results: PedsQL total and physical function and PODCI global, transfer/mobility and sports/physical function PROs demonstrated significant differences between DMD and controls (p<0.00001). In DMD, 6MWD and 10-meter run/walk velocity were correlated with PODCI domain scores, with the transfer/mobility scale showing the strongest relationship (r=0.79 and r=0.76). In DMD, 6MWD distance and 10-meter run/walk velocity weakly correlated with PedsQL domain scores. In DMD, 6MWD, 10-meter run/walk velocity, and PODCI global and transfer and basic mobility demonstrated significant one-year change and exceeded the amount of change representing MCID. In DMD, 6MWD change highly correlated with change in PODCI global and PODCI transfer/mobility scores (r=0.76 and r=0.93). PODCI global and PODCI transfer/mobility scales provided the best estimates of 6MWT performance. A “meaningful” 4.5 point change in a low PODCI transfer / basic mobility score of 30 to 34.5 was associated with a 5.6m 6MWD change from 150.3 to 155.9m. At PODCI levels closer to normative levels for healthy controls, the change in 6MWD distance associated with a “meaningful” change in PODCI scores was almost 46m. Discussion: At lower levels of function, smaller increases in 6MWD result in meaningful change in quality of life (QoL) instrument scores. At higher levels of function, larger increases may be necessary to achieve the same QoL change score.

The cooperative international neuromuscular research group Duchenne natural history study--a longitudinal investigation in the era of glucocorticoid therapy: design of protocol and the methods used

Contemporary natural history data in Duchenne muscular dystrophy (DMD) is needed to assess care recommendations and aid in planning future trials.

METHODS

The Cooperative International Neuromuscular Research Group (CINRG) DMD Natural History Study (DMD-NHS) enrolled 340 individuals, aged 2-28 years, with DMD in a longitudinal, observational study at 20 centers. Assessments obtained every 3 months for 1 year, at 18 months, and annually thereafter included: clinical history; anthropometrics; goniometry; manual muscle testing; quantitative muscle strength; timed function tests; pulmonary function; and patient-reported outcomes/health-related quality-of-life instruments.

RESULTS

Glucocorticoid (GC) use at baseline was 62% present, 14% past, and 24% GC-naive. In those ≥6 years of age, 16% lost ambulation over the first 12 months (mean age 10.8 years).

CONCLUSIONS

Detailed information on the study methodology of the CINRG DMD-NHS lays the groundwork for future analyses of prospective longitudinal natural history data. These data will assist investigators in designing clinical trials of novel therapeutics.

Motor and cognitive assessment of infants and young boys with Duchenne Muscular Dystrophy: results from the Muscular Dystrophy Association DMD Clinical Research Network

Therapeutic trials in Duchenne Muscular Dystrophy (DMD) exclude young boys because traditional outcome measures rely on cooperation. The Bayley III Scales of Infant and Toddler Development (Bayley III) have been validated in developing children and those with developmental disorders but have not been studied in DMD. Expanded Hammersmith Functional Motor Scale (HFMSE) and North Star Ambulatory Assessment (NSAA) may also be useful in this young DMD population. Clinical evaluators from the MDA-DMD Clinical Research Network were trained in these assessment tools. Infants and boys with DMD (n = 24; 1.9 ± 0.7 years) were assessed. The mean Bayley III motor composite score was low (82.8 ± 8; p ≤ .0001) (normal = 100 ± 15). Mean gross motor and fine motor function scaled scores were low (both p ≤ .0001). The mean cognitive comprehensive (p=.0002), receptive language (p ≤ .0001), and expressive language (p = .0001) were also low compared to normal children. Age was negatively associated with Bayley III gross motor (r = -0.44; p = .02) but not with fine motor, cognitive, or language scores. HFMSE (n=23) showed a mean score of 31 ± 13. NSAA (n = 18 boys; 2.2 ± 0.4 years) showed a mean score of 12 ± 5. Outcome assessments of young boys with DMD are feasible and in this multicenter study were best demonstrated using the Bayley III.

The cooperative international neuromuscular research group Duchenne natural history study: glucocorticoid treatment preserves clinically meaningful functional milestones and reduces rate of disease progression as measured by manual muscle testing and other commonly used clinical trial outcome measures

introduction: Glucocorticoid (GC) therapy in Duchenne muscular dystrophy (DMD) has altered disease progression, necessitating contemporary natural history studies.

METHODS

The Cooperative Neuromuscular Research Group (CINRG) DMD Natural History Study (DMD-NHS) enrolled 340 DMD males, ages 2-28 years. A comprehensive battery of measures was obtained.

RESULTS

A novel composite functional "milestone" scale scale showed clinically meaningful mobility and upper limb abilities were significantly preserved in GC-treated adolescents/young adults. Manual muscle test (MMT)-based calculations of global strength showed that those patients <10 years of age treated with steroids declined by 0.4 ± 0.39 MMT unit/year, compared with -0.4 ± 0.39 MMT unit/year in historical steroid-naive subjects. Pulmonary function tests (PFTs) were relatively preserved in steroid-treated adolescents. The linearity and magnitude of decline in measures were affected by maturational changes and functional status.

CONCLUSIONS

In DMD, long-term use of GCs showed reduced strength loss and preserved functional capabilities and PFTs compared with previous natural history studies performed prior to the widespread use of GC therapy.

24 month longitudinal data in ambulant boys with Duchenne muscular dystrophy

Objectives

The aim of the study was i) to assess the spectrum of changes over 24 months in ambulant boys affected by Duchenne muscular dystrophy, ii) to establish the difference between the first and the second year results and iii) to identify possible early markers of loss of ambulation.

Methods

One hundred and thirteen patients (age range 4.1–17, mean 8.2) fulfilled the inclusion criteria, 67 of the 113 were on daily and 40 on intermittent steroids, while 6 were not on steroids. All were assessed using the 6 Minute Walk Test (6MWT), the North Star Ambulatory Assessment (NSAA) and timed test.

Results

On the 6MWT there was an average overall decline of −22.7 (SD 81.0) in the first year and of −64.7 (SD 123.1) in the second year. On the NSAA the average overall decline was of −1.86 (SD 4.21) in the first year and of −2.98 (SD 5.19) in the second year. Fourteen children lost ambulation, one in the first year and the other 13 in the second year of the study. A distance of at least 330 meters on the 6MWT, or a NSAA score of 18 at baseline reduced significantly the risk of losing ambulation within 2 years.

Conclusions

These results can be of help at the time of using inclusion criteria for a study in ambulant patients in order to minimize the risk of patients who may lose ambulation within the time of the trial.