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Updated: Oct 11, 2025
Measuring the Functional Abilities of Children Aged 3-6 Years Old with Observational Methods and Computer Tools
Published on: June 20, 2020
Analysis of cognitive ability and adaptive behavior assessment tools used in an observational study of patients with
Karen S Yee1, Yanyu Wu2, Magdalena Harrington3,4
1Takeda Development Center Americas, Inc., Cambridge, MA, USA. karen.yee@takeda.com.
Background:
Mucopolysaccharidosis II (MPS II) is a rare lysosomal storage disease characterized by cognitive impairment in most patients. This post hoc analysis evaluated changes in cognitive function, adaptive behavior and functional outcomes in patients with neuronopathic MPS II over time. Fifty-five children with MPS II were enrolled in a 24-month observational study (NCT01822184). The Differential Ability Scales, second edition (DAS-II; early years battery for ages 2 years 6 months to 6 years 11 months, school age battery for ages 7 years to 17 years 11 months), Vineland Adaptive Behavior Scales, second edition (VABS-II) and the Hunter Syndrome-Functional Outcomes for Clinical Understanding Scale (HS-FOCUS) were performed at baseline and 3-month intervals over 2 years. A subgroup of 38 children with a DAS-II General Conceptual Ability (GCA) score of 55-85 (below average-very low abilities) at any time during the study were included in this analysis.
Results:
Mean (standard deviation [SD]) early years DAS-II GCA score decreased from 73.4 (15.7, n = 22) at baseline to 62.7 (34.9, n = 6) at month 24. For the six patients with early years GCA assessments at baseline and month 24, mean (SD) GCA scores decreased from 72.3 (21.3) at baseline to 62.7 (34.9) at month 24. School age GCA scores were stable over 2 years: mean (SD) 72.4 (11.8, n = 10) at baseline; 74.3 (12.3, n = 8) at month 24. Mean (SD) VABS-II Adaptive Behavior Composite (ABC) scores were stable throughout the study (baseline, 81.8 [11.8, n = 36]; month 24, 81.0 [10.2, n = 13]). Some associations between items and domains of HS-FOCUS (p < 0.05) and DAS-II GCA and VABS-II ABC scores were shown, but there was no clear pattern of changes in HS-FOCUS over 2 years.
Conclusions:
The DAS-II measured changes in cognitive function over 2 years in younger patients with MPS II, whereas cognitive function in older patients remained stable. Further research is required to confirm the content validity of the DAS-II in different patient populations with MPS II. The VABS-II and HS-FOCUS were not sensitive tools for measuring behavioral and functional changes over 2 years. These findings may inform selection of appropriate cognitive and behavioral assessment tools for future studies.
Insights
Cognitive function declined in younger patients with Mucopolysaccharidosis II (MPS II) over two years, while older patients remained stable. Current behavioral and functional tools may not be sensitive enough for tracking changes in MPS II patients.
Area of Science:
- Neurology
- Genetics
- Pediatrics
Background:
- Mucopolysaccharidosis II (MPS II), a rare lysosomal storage disease, often presents with cognitive impairment.
- Neuronopathic MPS II specifically affects cognitive function, necessitating longitudinal assessment.
- This study focuses on evaluating cognitive, behavioral, and functional changes in children with neuronopathic MPS II.
Purpose of the Study:
- To assess changes in cognitive function, adaptive behavior, and functional outcomes in children with neuronopathic MPS II over a 24-month period.
- To evaluate the utility of specific assessment tools in tracking these changes.
- To identify potential patterns of decline or stability in cognitive and functional measures.
Main Methods:
- A 24-month observational study (NCT01822184) enrolled 55 children with MPS II.
- Cognitive function was assessed using the Differential Ability Scales, second edition (DAS-II).
- Adaptive behavior was measured with the Vineland Adaptive Behavior Scales, second edition (VABS-II), and functional outcomes with the Hunter Syndrome-Functional Outcomes for Clinical Understanding Scale (HS-FOCUS).
Main Results:
- Younger patients (early years battery) showed a decrease in DAS-II General Conceptual Ability (GCA) scores over 24 months.
- Older patients (school age battery) exhibited stable DAS-II GCA scores.
- Vineland Adaptive Behavior Scales, second edition (VABS-II) scores remained stable, and the Hunter Syndrome-Functional Outcomes for Clinical Understanding Scale (HS-FOCUS) did not show clear patterns of change.
Conclusions:
- The DAS-II detected cognitive changes in younger MPS II patients, while older patients' cognition remained stable.
- The VABS-II and HS-FOCUS demonstrated limited sensitivity for measuring 2-year changes in behavior and function.
- Findings suggest careful selection of assessment tools for future MPS II studies is crucial.
