Article

Quality of Life Research

, Volume 18, Issue 3, pp 359-370

First online:

Measuring global physical health in children with cerebral palsy: illustration of a multidimensional bi-factor model and computerized adaptive testing

  • Stephen M. HaleyAffiliated withHealth and Disability Research Institute, Boston University School of Public Health Email author 
  • , Pengsheng NiAffiliated withHealth and Disability Research Institute, Boston University School of Public Health
  • , Helene M. DumasAffiliated withResearch Center for Children with Special Health Care Needs, Franciscan Hospital for Children
  • , Maria A. Fragala-PinkhamAffiliated withResearch Center for Children with Special Health Care Needs, Franciscan Hospital for Children
  • , Ronald K. HambletonAffiliated withDepartment of Educational Policy, Research and Administration, Center for Educational Assessment, University of Massachusetts
  • , Kathleen MontpetitAffiliated withDepartment of Occupational Therapy, Shriners Hospital for Children
  • , Nathalie BilodeauAffiliated withDepartment of Occupational Therapy, Shriners Hospital for Children
  • , George E. GortonAffiliated withMotion Lab, Shriners Hospital for Children
  • , Kyle WatsonAffiliated withMotion Analysis Lab, Shriners Hospital for Children
    • , Carole A. TuckerAffiliated withPhysical Therapy Department, College of Health Professions, Temple University

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Abstract

Purpose

The purposes of this study were to apply a bi-factor model for the determination of test dimensionality and a multidimensional CAT using computer simulations of real data for the assessment of a new global physical health measure for children with cerebral palsy (CP).

Methods

Parent respondents of 306 children with cerebral palsy were recruited from four pediatric rehabilitation hospitals and outpatient clinics. We compared confirmatory factor analysis results across four models: (1) one-factor unidimensional; (2) two-factor multidimensional (MIRT); (3) bi-factor MIRT with fixed slopes; and (4) bi-factor MIRT with varied slopes. We tested whether the general and content (fatigue and pain) person score estimates could discriminate across severity and types of CP, and whether score estimates from a simulated CAT were similar to estimates based on the total item bank, and whether they correlated as expected with external measures.

Results

Confirmatory factor analysis suggested separate pain and fatigue sub-factors; all 37 items were retained in the analyses. From the bi-factor MIRT model with fixed slopes, the full item bank scores discriminated across levels of severity and types of CP, and compared favorably to external instruments. CAT scores based on 10- and 15-item versions accurately captured the global physical health scores.

Conclusions

The bi-factor MIRT CAT application, especially the 10- and 15-item versions, yielded accurate global physical health scores that discriminated across known severity groups and types of CP, and correlated as expected with concurrent measures. The CATs have potential for collecting complex data on the physical health of children with CP in an efficient manner.

Keywords

Bi-factor model Computerized adaptive testing Item response theory