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Validation of the shortened Hunter Syndrome-Functional Outcomes for Clinical Understanding Scale (HS-FOCUS)
Maria Mattera1, Margaret K Vernon1, Mireia Raluy-Callado2
1Evidera, 7101 Wisconsin Avenue, Suite 1400, Bethesda, MD, 20814, USA.
Background:
The rare disease, Hunter Syndrome (mucopolysaccharidosis type II; MPS II), characterized by iduronate-2-sulfatase deficiency, has heterogeneous symptoms often including cognitive impairment (CI). To evaluate physical functioning and daily activity limitations of patients with MPS II, the multidomain shortened Hunter Syndrome-Functional Outcomes for Clinical Understanding Scale (HS-FOCUS) questionnaire was previously developed and preliminarily validated. Here we gather data in a dedicated prospective longitudinal observational study using direct responses to the shortened instrument and assess its psychometric properties further.
Methods:
Interview data were collected from eligible self-reporting patients (≥ 12 years of age) or caregivers of patients using respective versions of the instrument at baseline and 2-4 weeks later. Internal consistency, test-retest reliability, convergent and discriminant validity, and validity of known groups were assessed. Participants also completed Child Health Questionnaire (CHQ), Health Utilities Index Mark 3, and Global Impression of Severity (GIS) questionnaires.
Results:
All patients were male, consisting of 31 caregiver-reported patients (aged 3-26 years) and 20 self-reported patients (aged 12-58 years). Most (77.4%) caregiver-reported patients had CI. Both questionnaire versions demonstrated good internal consistency and test-retest reliability; Cronbach's alpha and intra-class correlation coefficients were > 0.70. Spearman's correlations demonstrated good convergent validity with moderate (> 0.3) to high (> 0.6) correlations of the HS-FOCUS total score with physical functioning, role/social-physical, and bodily pain domains of CHQ. The tool also differentiated between MPS II severity levels based on GIS scores.
Conclusions:
The shortened HS-FOCUS questionnaire was found to be a valid and reliable tool to assess the physical functioning impact of MPS II.
Insights
The shortened HS-FOCUS questionnaire effectively measures physical functioning in Hunter Syndrome (MPS II) patients. This validated tool aids in assessing daily activity limitations for individuals with this rare genetic disorder.
Area of Science:
- Rare disease research
- Clinical outcome assessment
- Patient-reported outcomes
Background:
- Hunter Syndrome (mucopolysaccharidosis type II; MPS II) is a rare genetic disorder caused by iduronate-2-sulfatase deficiency.
- Symptoms are heterogeneous, often including cognitive impairment, impacting daily life and physical functioning.
- The shortened Hunter Syndrome-Functional Outcomes for Clinical Understanding Scale (HS-FOCUS) was developed to evaluate these limitations.
Purpose of the Study:
- To further validate the psychometric properties of the shortened HS-FOCUS questionnaire in patients with MPS II.
- To assess the reliability and validity of the HS-FOCUS for evaluating physical functioning and daily activity limitations.
- To gather prospective longitudinal data using the HS-FOCUS instrument.
Main Methods:
- A prospective longitudinal observational study collected interview data from self-reporting patients (≥12 years) and caregivers.
- Data were collected at baseline and a 2-4 week follow-up to assess test-retest reliability.
- Internal consistency, convergent/discriminant validity, and known-groups validity were evaluated using Cronbach's alpha, ICC, and correlation analyses with other validated questionnaires (CHQ, HUI Mark 3, GIS).
Main Results:
- The study included 31 caregiver-reported patients (3-26 years) and 20 self-reported patients (12-58 years); all were male.
- The HS-FOCUS demonstrated good internal consistency (Cronbach's alpha > 0.70) and test-retest reliability (ICC > 0.70).
- Convergent validity was supported by moderate to high correlations with CHQ domains, and the tool differentiated between MPS II severity levels.
Conclusions:
- The shortened HS-FOCUS questionnaire is a valid and reliable instrument for assessing the impact of MPS II on physical functioning.
- The findings support the use of HS-FOCUS in clinical settings to evaluate physical function and daily activity limitations in MPS II patients.
- This validated tool can aid clinicians in understanding the functional consequences of Hunter Syndrome.
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