Short developmental milestone risk assessment tool to identify Duchenne muscular dystrophy in primary care

BACKGROUND

In patients without a family history, Duchenne muscular dystrophy (DMD) is typically diagnosed at around 4-5 years of age. It is important to diagnose DMD during infancy or toddler stage in order to have timely access to treatment, opportunities for reproductive options, prevention of potential fatal reactions to inhaled anesthetics, awareness of a child's abilities needed for good parenting, and opportunities for enrolment in clinical trials.

METHOD

We aimed to develop a short risk assessment tool based on developmental milestones that may contribute to the early detection of boys with DMD in primary care. As part of the case-control 4D-DMD study (Detection by Developmental Delay in Dutch boys with DMD), data on developmental milestones, symptoms and therapies for 76 boys with DMD and 12,414 boys from a control group were extracted from the health records of youth health care services and questionnaires. Multiple imputation, diagnostic validity and pooled backward logistic regression analyses with DMD (yes/no) as the dependent variable and attainment of 26 milestones until 36 months of age (yes/no) as the independent variable were performed. Descriptive statistics on symptoms and therapies were provided.

RESULTS

A tool with seven milestones assessed at specific ages between 12 and 36 months resulted in a sensitivity of 79% (95CI:67-88%), a specificity of 95.8% (95%CI:95.3-96.2), and a positive predictive value of 1:268 boys. Boys with DMD often had symptoms (e.g. 43% had calf muscle pseudohypertrophy) and were referred to therapy (e.g. 59% for physical therapy) before diagnosis.

DISCUSSION

This tool followed by the examination of other DMD-related symptoms could be used by youth health care professionals during day-to-day health assessments in the general population to flag children who require further action.

CONCLUSIONS

The majority of boys (79%) with DMD can be identified between 12 and 36 months of age with this tool. It increases the initial a priori risk of DMD from 1 in 5,000 to approximately 1 in 268 boys. We expect that other neuromuscular disorders and disabilities can also be found with this tool.

Early developmental milestones in Duchenne muscular dystrophy

AIM

To investigate the differences in attainment of developmental milestones between young males with Duchenne muscular dystrophy (DMD) and young males from the general population.

METHOD

As part of the case-control 4D-DMD study (Detection by Developmental Delay in Dutch boys with Duchenne Muscular Dystrophy), data on developmental milestones for 76 young males with DMD and 12 414 young males from a control group were extracted from the health care records of youth health care services. The characteristics of DMD were acquired from questionnaires completed by parents. Logistic regression analyses were performed with milestone attainment (yes/no) as the dependent variable and DMD (yes/no) as the independent variable, with and without adjustment for age at visit.

RESULTS

The mean number of available milestones was 43 (standard deviation [SD]=13, range: 1-59) in the DMD group and 40 (SD=15, range: 1-60) in the control group. The presence of developmental delay was evident at 2 to 3 months of age, with a higher proportion of young males with DMD failing to attain milestones of gross/fine motor activity, adaptive behaviour, personal/social behaviour, and communication (range age-adjusted odds ratios [ORs]=2.3-4.0, p<0.01). Between 12 and 36 months of age, differences in the attainment of developmental milestones concerning gross motor activity increased with age (range age-adjusted ORs=10.3-532, p<0.001). We also found differences in developmental milestones concerning fine motor activity, adaptive behaviour, personal/social behaviour, and communication between 12 and 48 months of age (range age-adjusted ORs=2.5-9.7, p<0.01).

INTERPRETATION

We found delays in the attainment of motor and non-motor milestones in young males with DMD compared to the control group. Such delays were already evident a few months after birth. Developmental milestones that show a delay in attainment have the potential to aid the earlier diagnosis of DMD.