Functional assessments used in routine care for duchenne muscular dystrophy in the United States: A survey of certified duchenne care centers

Abstract

Background

Clinical decision-making, disease progression monitoring, and evaluation of novel therapies for patients with Duchenne muscular dystrophy (DMD) rely on functional assessments. This study aimed to evaluate the use of functional assessments in routine DMD care and identify challenges encountered in their administration and documentation.

Methods

A cross-sectional online survey was conducted in 2023 among 36 Certified Duchenne Care Centers (CDCCs) in the United States. Center directors collaborated with multidisciplinary teams to provide single response per center. The survey encompassed functional assessments for ambulatory and non-ambulatory patients, milestones definitions, documentation practices, and perceived barriers.

Results

Twenty-three CDCCs responded to the survey. Nearly half of the centers cared for up to 200 patients with DMD in the previous year, and all used electronic health record systems. Functional assessments were routinely conducted for both ambulatory and non-ambulatory patients, though variability was observed in assessment implementation, standardization procedures, training practices, documentation, and milestone definitions. Consistent use of assessments was reported in ambulatory patients; however, the extent of formal training and use of documented standard operating procedures varied across centers. Definitions of loss of ambulation were heterogeneous and often depended on the assessor’s judgment. The most frequently reported barriers to conducting and documenting functional assessments included limited clinic time, insufficient staff hours, patient and caregiver burden, lack of convenient data-entry tools, and the time required for documentation.

Conclusions

The study provides an overview of functional assessment practices at CDCCs and identifies important opportunities to harmonize assessment implementation, documentation, and milestone definitions across centers.

Introduction

Duchenne muscular dystrophy (DMD) is an X-linked recessive, progressive, and ultimately fatal neuromuscular disorder caused by pathogenic variants in the DMD gene. These variants result in either the absence or the production of a dysfunctional protein dystrophin, which is essential for maintaining muscle integrity.^1–3 Due to its inheritance pattern, the disorder predominantly affects males, with an incidence estimated at approximately 1 in 3,000 to 5,000 male births.^4,5 The clinical characteristics of DMD include progressive muscle weakness, loss of ambulation, respiratory and cardiac complications, and premature mortality. ⁶ Despite advancements in multidisciplinary care, treatments including gene therapy, advanced and proactive respiratory care, and cardiac management, resulting in improved quality of life and extended life expectancy, the progressive nature of the disease necessitates continuous monitoring of functional abilities to inform clinical decisions, optimize care, and assess the efficacy of emerging therapies.

Standardized functional assessments facilitate the provision of consistent and objective measures in disease progression.^7,8 They enable clinicians to monitor changes in motor function, mobility, and independence over time, which is particularly important in patients with DMD given the high variability of its effects among patients. ⁹ Furthermore, these assessments assist in identifying the necessity for interventions such as physical therapy, orthotic devices, or surgical procedures. The loss of ambulation constitutes a critical milestone in DMD, and early detection of declining mobility can prompt the initiation of interventions aimed at prolonging ambulation. ¹⁰ Importantly, selected functional assessments also serve to measure end outcomes in clinical trials, thereby evaluating the efficacy of proposed interventions, especially in the context of emerging disease modifying therapies. ¹¹ The DMD care considerations emphasize the importance of utilizing functional assessments as a component of DMD management. Nonetheless, the selection of appropriate tools should be based on the patient’s age, functional status, specific needs, and the feasibility of administration within clinical settings. ¹⁰

Numerous functional assessments have been developed and validated for application in DMD. These assessments are designed to evaluate various aspects of functional ability, including ambulation and upper-limb function. The 6-Minute Walk Test (6MWT) is used to assess ambulatory function in individuals with DMD by measuring the distance walked in 6 minutes, providing indices of endurance and mobility.^12,13 However, its applicability is limited to ambulatory patients. The North Star Ambulatory Assessment (NSAA) comprises 17 items that assess standing, walking, running, and jumping. The NSAA demonstrates high sensitivity to changes in ambulatory status and has been validated for use in clinical trials.^14–17 The Performance of the Upper Limb (PUL) scale is designed to assess upper-limb function, particularly in patients who have lost ambulation. Patients are required to perform specific upper-limb activities that provide measures of their proximal, mid-level, and distal limb capabilities.^18–20 Several functional tests involve timing patients’ movements, including the time required to walk/run 10 meters (10MWT), rise from the floor (RFS), ascend four stairs, and rise from a chair. These tests evaluate lower-limb function and are routinely employed in clinical practice. The Motor Function Measure (MFM) is designed to assess three primary domains: standing and transfers, axial and proximal motor function, and distal motor function. It is applicable to both ambulatory and non-ambulatory patients, although it may be somewhat cumbersome to administer.^21,22 Lastly, the Brookes and Vignos scales assess lower- and upper-limb function, respectively. Although these scales are less sensitive, their simplicity and ease of administration sustain their continued use in clinical settings.^23,24,25

In our study, we aimed to understand the current use of functional assessments during standard-of-care clinic visits for ambulatory and non-ambulatory DMD patients, as well as the challenges in conducting and documenting such assessments in Certified Duchenne Care Centers (CDCCs).

Methods

A cross-sectional survey was administered to CDCCs in the United States (US) via an online questionnaire in 2023 to determine the functional assessments used at the centers and their key challenges in administration. The CDCC program is a unique program of Parent Project Muscular Dystrophy aiming to ensure that all individuals with Duchenne and Becker have access to high quality, comprehensive, and coordinated care and research. CDCCs undergo a rigorous application process and in person evaluation to ensure they meet strict criteria including having experienced Duchenne specialists, offering coordinated care, and providing comprehensive services and treatments in line with the current standards of care.

Survey development and content

The survey was developed by the study team in collaboration with clinical experts in DMD care. The survey was designed to characterize current practices for conducting and documenting functional assessments during routine clinical care at CDCCs in the US. The survey included 28 questions encompassed several major domains, including care center characteristics, current use of motor function assessments in ambulatory and non-ambulatory DMD, definitions and documentation of key milestones, documentation practices, and perceived challenges related to conducting and documenting functional assessments. Questions included single-choice, multiple-choice, ranking, and open-text response formats. Respondents ranked applicable challenges associated with conducting and documenting functional assessments using predefined response options, with opportunities to provide additional free-text comments.

Survey administration

The survey was administered online between September and November 2023 to all 36 CDCCs in the US. Informed consent was obtained electronically prior to survey completion. Center Directors were asked to coordinate with the multidisciplinary clinic team to complete a single survey representing their center. Reminder emails were sent to non-responding centers during the survey period to encourage participation. Only one response per center was included in the analysis, and surveys that were not completed were excluded.

Data analysis

This was a descriptive study; therefore, no inferential statistical analyses or hypothesis testing were performed. Survey responses were summarized using descriptive statistics. Categorical variables were reported as frequencies and proportions. Rankings for challenges related to conducting functional assessments ranged from 1 to 10, and rankings for challenges related to documenting functional assessments ranged from 1 to 5, with lower rankings indicating greater perceived challenges. To visualize the distribution and relative importance of reported challenges across centers, heat maps were generated, with color intensity representing the frequency of each ranking assigned to a given challenge. Analyses were performed using R version 4.3.0, and charts and figures were developed using Microsoft Excel.

Results

Participating centers

Of the 36 CDCCs in the United States, 23 responded to the survey. Nearly half of the participating centers cared for up to 200 DMD patients each during the previous year and most reported that half of their patients were ambulatory. The large majority were pediatric hospitals, though some continued to see small numbers of adult DMD patients. DMD registrational trials were conducted at 87% of the centers, with over half of them having conducted trials for over 8 years, some having as many as 10-15 ongoing trials at the time of the survey. Nearly all CDCCs collected data outside clinical trials, and over half of the centers have researchers working full- or part-time on data entry and management (Table 1).

Table 1.

DMD care center and survey respondent characteristics.

a. Center characteristics
Center characteristics	Centers (N = 23)
Number of DMD patients followed during the past year
11-20 patients	1 (4.3%)
21-50 patients	1 (4.3%)
51-100 patients	9 (39.1%)
101-200 patients	11 (47.8%)
>300 patients	1 (4.3%)
Percentage of DMD patients that were ambulatory at any time during the past year
11-30% ambulatory patients	4 (17.4%)
31-50% ambulatory patients	18 (78.3%)
51-90% ambulatory patients	1 (4.3%)
Center’s participation in registrational clinical trials for DMD
Yes	20 (87.0%)
Number of years center has conducted registrational trials in DMD
No patient yet enrolled in, but study set-up underway	1 (5.0%)
≤2 years	2 (10.0%)
5-6 years	2 (10.0%)
7-8 years	3 (15.0%)
>8 years	12 (60.0%)
Number of currently ongoing registrational trials in DMD at center
1-2 trials	8 (40.0%)
3-4 trials	5 (25.0%)
4-6 trials	2 (10.0%)
7-8 trials	1 (5.0%)
9-10 trials	2 (10.0%)
10-15 trials	2 (10.0%)
No	3 (13.0%)
Whether center collects DMD clinical data for research outside of registrational clinical trials 1	21 (91.3%)
Yes, data routinely collected from all clinic visits are curated for research, with patient consent	11 (52.4%)
Yes, occasionally for specific study protocols (non-registrational)	6 (28.6%)
Yes, other 2	3 (14.3%)
No	1 (4.8%)
Number of research staff responsible for direct data entry and management (full-time and part-time) 1	21 (91.3%)
≤2 research staff	4 (19.0%)
3-6 research staff	11 (52.4%)
7-9 research staff	3 (14.3%)
≥10 research staff	3 (14.3%)
EHR system(s) used 3
Epic	16 (69.6%)
Cerner	7 (30.4%)
Allscripts	2 (8.7%)
PowerChart	1 (4.3%)

DMD, Duchenne Muscular Dystrophy; EHR, electronic health record.

¹Data are not available for 2 centers. Proportions of subitems are calculated based on the centers that answered this question.

²One center collects data for registries; one center collects data for quality assurance purpose; one center is unsure.

³Participants are allowed to select more than one response; therefore, the total proportions may exceed 100%.

Key assessments and standardization

Functional assessments for patients with DMD are routinely conducted at most centers; however, variability was observed in the specific assessments used, their frequency of administration, and the degree of standardization. Among ambulatory DMD patients, assessments such as the NSAA, 10MWT, RFS, and the Brooke upper-extremity rating scale are routinely performed in more than 50% of visits (Figure 1(a)). However, the extent of formal training and use of documented standard operating procedures (SOPs) varied across centers; while some centers reported having documented training and SOPs in place, others relied on examiner-specific subjective judgment or had no formal training guidelines (Figure 1(b)).

Figure 1.

Use and standardization of motor function assessments in ambulatory and non-ambulatory DMD across participating CDCCs. Panels (A) and (C) show the frequency with which individual motor function assessments are performed during routine care in ambulatory and non-ambulatory patients, respectively. Panels (B) and (D) show the reported degree of standardization and training for each assessment. This figure highlights variability across centers in both the frequency of assessment administration and the degree of standardization and training.

Definitions of key clinical milestones, such as “loss of ambulation,” are heterogeneous across centers and often depend on the assessor’s judgment. Only one-third of centers reported using a standard definition for loss of ambulation, with common criteria including the inability to complete a 10MWT. Brooke and, to a lesser extent, PUL 2.0 are the predominant measures in both ambulatory and non-ambulatory upper-body assessments.

Similar variability was observed for assessments in non-ambulatory DMD. Assessments such as head lifting, transfer to sitting, and the Brooke Scale are performed at the minimum standard of care (Figure 1(c)). Only 34.8% of centers have documented training and SOPs in place for these assessments, while the remainder relied on less formal approaches or reported no standardized training (Figure 1(d)).

Challenges in functional data collection

The survey identified several barriers to both conducting and documenting functional assessments (Figures 2 and 3). For documentation, the lack of convenient tools for data-entry was most frequently ranked as a top barrier, followed by insufficient staff time and the time-consuming nature of documentation. Documentation of standardized or quantitative assessments not being incorporated into routine workflows was also commonly ranked among the more important barriers, whereas lack of perceived added value for patient care was generally assigned lower-priority rankings (Figure 2).

Figure 2.

Ranked barriers to documenting functional assessments during routine DMD care. Heatmap showing how participating centers ranked 5 predefined barriers to documentation from most impactful (Rank 1) to least impactful (Rank 5). Reported barriers include a lack of convenient digital tools for data entry, insufficient staff time and workload constraints, the absence of standardized quantitative assessment documentation in routine workflow, and low perceived added value for patient care. “Other” category captures additional site-specific concerns not encompassed by the predefined barrier categories. Warmer colors indicate higher counts of centers selecting a barrier for a given rank, with darker intensity corresponding to greater frequency.

Figure 3.

Ranked barriers to conducting functional assessments during routine DMD care. Heatmap showing how participating centers ranked 10 predefined barriers to assessment administration from most impactful (Rank 1) to least impactful (Rank 10). Barriers evaluated include limited patient time during routine visits, lack of staff hours, physical or emotional burden on patients or caregivers, insufficient funding or equipment, limited provider training, inconvenient access to assessment measures, redundancy with clinical tests, exclusion of assessments from standard workflows, and perceived lack of added value. “Other” includes respondent-specified barriers not listed among predefined categories. Warmer colors indicate higher counts of centers selecting a barrier for a given rank, with darker intensity corresponding to greater frequency.

For assessment administration, limited time available during routine visits was ranked as the greatest challenge by 8 centers, followed by insufficient staff hours and the inconvenience of data entry. Physical and emotional burden on patients and caregivers, lack of funding for training and equipment, and limited access to assessment apparatus were also commonly reported barriers. In contrast, exclusion of assessments from routine workflows and lack of perceived added value for patient care were generally assigned lower-priority rankings (Figure 3).

Assessments when patients struggle

Approximately one-third of participating centers reported that functional assessments are relatively commonly not conducted when a patient is expected to struggle significantly or is very likely to be unable to perform the assessment. However, 56.5% of centers reported that assessments are almost always attempted except in rare circumstances (Figure 4, left panel). When assessments are not conducted, most centers reported that specific reasons for non-assessment were always or almost always documented in the medical record (16 centers), while four centers reported that results or notes were usually left blank or that the non-attempt was not documented and three centers reported other documentation practices (Figure 4, right panel).

Figure 4.

Center practices when functional assessments are not performed. Left: Responses describing whether functional assessments are conducted when a patient is expected to struggle significantly or be unable to complete the assessment. Right: Responses describing how instances in which a functional assessment is not conducted are documented in the medical record.

Discussion

Functional outcome measures are central to clinical decision making, trial readiness, and real-world evidence generation in DMD; however, their utility depends on consistent application and shared definitions. Our findings highlight that, despite widespread use of established tools for functional assessments and alignment with recommended standard-of-care assessments, ¹ substantial variability persists across centers. This variability included differences in the subset of assessments routinely administered and the definitions and operational criteria used for clinically important milestones, particularly loss of ambulation. Variation across centers in the subset of routinely used functional assessments may reflect the wide range of available measures in DMD as well as center-specific historical practices and clinician preferences. Given the time required for staff training and assessment administration, centers must select only a subset of measures. Some degree of center-level variation may therefore be clinically appropriate. Nevertheless, variation in functional assessment selection, administration procedures, and assessor training may reduce the comparability of functional data collected across centers or over time. Such variation may also complicate interpretation when patients transition between centers or when data from multiple centers are combined for quality-improvement or research purposes. The variability observed in definitions of key milestones has additional implications. Loss of ambulation may be defined according to different criteria, such as inability to do a 10 meter walk test, inability to take any independent steps, or based on NSAA item 2. Consequently, patients with similar functional abilities could be classified differently across centers. Inconsistent milestone definitions may affect estimates of the timing and frequency of clinically important events and limit the comparability of clinical records and multicenter datasets. Establishing consensus-based core assessments, along with clear definitions and standardized operational criteria for key functional milestones, represents an important opportunity to improve data harmonization and may enhance the value of functional assessment data for multicenter clinical care and future research.

The results indicate several opportunities to improve the conduct and documentation of functional assessments in routine DMD care. Consistent with the barriers reported by participating centers, there is a need for more efficient clinical workflows, improved data-entry tools, and increased resources to support staff training and assessment equipment. Implementing electronic data-entry tools or applications could streamline the process and reduce staff workload. Also, increasing the documentation of key milestones, such as loss of ambulation, with standardized definitions would improve the consistency and reliability of data across centers. An additional opportunity identified is more consistent documentation of the reasons why functional assessments are not performed. Although most centers reported routinely documenting specific reasons for non-assessment, a sizable minority did not. More consistent documentation of non-assessment and loss of functional ability could improve longitudinal patient monitoring and may enhance the usefulness of clinical data for future quality improvement and research. Additionally, while the full NSAA is routinely conducted at most CDCCs, a shortened version may be helpful at other centers to reduce the burden on patients and staff. The development of the 6-item NSAA proxy, which has been validated across various subpopulations, offers a promising solution for simplifying motor function assessments without compromising accuracy for the total score, enabling benchmarking of real-world outcomes against those measured with the full NSAA in clinical trials. Reducing the burden on both patients and staff will be critical to improving the quality and consistency of functional data collection. However, it is important to acknowledge the dual function of assessment time. While administration time was frequently cited as a barrier, the time invested in conducting assessments also serves a direct therapeutic purpose. The systematic observation required for each assessment serves to identify specific functional deficits that can directly inform rehabilitation goals and physiotherapy interventions. At the studied care centers, and in the US generally, functional data are primarily documented in medical records to support direct patient care, care management, and quality assessment (e.g., chart audits). In contrast to countries such as the UK and France, the US does not have a comprehensive national DMD registry. Clinical data captured in US electronic health records, especially at CDCCs, therefore play an important secondary role for use in research subject to data quality and appropriate ethics approvals.

The survey findings suggest that many CDCCs have infrastructure that could support future real-world data studies. Nearly all participating centers reported collecting clinical data outside registrational trials, and over half employed dedicated research staff responsible for clinical data entry and management, suggesting active engagement in both clinical care and research. Most CDCCs use EHR systems, with Epic being the most widely used, and they gather clinical data for research outside clinical trials. The widespread use of electronic health records, collection of clinical data outside registrational trials, and availability of dedicated research staff suggest that many CDCCs have infrastructure that may facilitate future observational research. However, the survey did not evaluate the quality, completeness, or suitability of these data for research purposes. The variability in assessment implementation, documentation practices, and milestone definitions identified in this survey highlights the importance of improving standardization before such data can be more consistently used across centers for quality improvement or research. When standardized tests and definitions are applied consistently, targeted studies based on chart reviews or electronic health record data from CDCCs may provide valuable insights into DMD progression and treatment outcomes. However, the extent to which current data practices support such research applications requires further evaluation.

The study has several limitations that should be considered when interpreting the generalizability of the findings. The results are based on centers that responded voluntarily; although the response rate is high, it is not fully representative of other non-participating CDCCs or non-CDCCs. Data were self-reported by the CDCC team without external verification, introducing a possibility of subjective interpretation of survey items, and variability in how centers interpret terms such as “routine care” or “standard of care visit”. The survey also did not collect patient-level or assessor-level data, preventing assessment of how functional assessments vary by age, disease stage, or clinical complexity, or other factors that could impact the feasibility and appropriateness of specific tools, or across different physiotherapists or care teams. Finally, the study did not evaluate how differences in staffing models, clinic workflows, or EHR capabilities directly influence functional assessment practices, limiting the ability to identify causal drivers of variability. Future surveys of non-CDCCs would be valuable to understand DMD care delivery and use of functional assessments more broadly. While our survey focused on functional assessments and documentation at US CDCCs, a recent survey of care centers in the UK evaluated comprehensively evaluated standard of care delivery from the clinician and patients/caregivers’ perspectives. ²⁶ Similar comprehensive and multi-perspective surveys would be valuable in the US as well.

Assessment practices in DMD may be evolving in response to newer treatments, including the need for closer monitoring associated with therapies such as AAV-mediated gene therapy. These advances may influence the frequency, type, and context of functional and safety assessments in clinical care. ²⁷ However, we note that the core challenges highlighted by our survey, such as variability in access to assessments, burden on patients and families, and differences in implementation across centers, are unlikely to have fundamentally changed. While specific practices may continue to adapt, we believe the overarching themes and barriers identified remain highly relevant in the current (2025–2026) landscape.

Conclusion

The study provides a contemporary overview of functional assessment practices at CDCCs in the US and identifies important opportunities to improve consistency across centers. Although the majority of CDCCs routinely conduct critical assessments for both ambulatory and non-ambulatory DMD patients, variability was observed in assessment implementation, standardization procedures, training practices, documentation, and definitions of key functional milestones across centers. Greater standardization of core functional assessments, documentation practices, and milestone definitions, together with improvements in clinical workflows, data-entry tools, staffing resources, and training, may improve the consistency and comparability of functional assessment data across centers. The widespread use of EHR systems and routine clinical data collection at CDCCs may provide a foundation for future real-world data studies, though addressing the variability identified in this survey will further increase this Potential. These findings indicate what functional data are likely to be collectable from medical records at CDCCs and provide prioritization for future efforts to harmonize functional assessment practices and documentation across CDCCs, supporting more consistent clinical care and future research initiatives in DMD.

Appendix.

Abbreviations

4SC

Timed 4-stair climb

6MWD

6-minute walk distance

10MWT

Timed 10-meter walk/run

30FtWT

Timed 30-foot walk/run

100MWT

Timed 100-meter walk/run

DMDDuchenne Muscular DystrophyMFM

Duchenne Muscular DystrophyMFMMotor function measurement

NSAA

North Star Ambulatory Assessment

RFS

Timed rise from supine

SOP

Standard operating procedure

STS

Timed sit to stand

CDCC

Certified Duchenne Care Centers

PPMD

Parent Project Muscular Dystrophy

Brooke

Brooke upper extremity rating scale

EK

Egan Klassification scale

PUL 1.2

Performance of the upper limb 1.2

PUL 2.0

Performance of the upper limb 2.0.

Ethical considerations

This article does not contain any studies with human or animal participants.

Consent to participate

A waiver of the informed consent process and HIPAA was requested and approved, as this research involved no more than minimal risk to the subjects.

Data Availability Statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on request.*