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

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.

Appendix: Global Physical Health Scale

• How often is your child’s neck stiff?

• How often is your child’s body stiff?

• How often is at least one of your child’s arms stiff?

• How often is at least one of your child’s legs stiff?

• How often does your child have trouble holding his/her head up when he/she is physically tired?

• How often does your child get physically tired when sitting in a chair or wheelchair at home or at school for more than 1 h?

• How often does your child have trouble changing positions because he/she is physically tired?

• How often does your child have trouble with transfers because he/she is physically tired?

• How often does your child have trouble standing for 5 min because he/she is physically tired?

• How often does your child have trouble walking because he/she is physically tired?

• How often does your child have trouble climbing a flight of 8–12 steps because he/she is physically tired?

• How often does your child have trouble running because he/she is physically tired?

• How often does your child have trouble playing games or sports with other children because he/she is physically tired?

• How often does your child trip and fall because he/she is physically tired?

• How often does your child have difficulty getting around by him/herself because he/she is physically tired?

• How often does your child have difficulty with school activities because he/she is physically tired?

• How often does your child have difficulty concentrating on homework, reading, or quiet activities because he/she is physically tired?

• How often does your child need time during the day to rest?

• How often does your child have difficulty doing activities after a day of school because he/she is physically tired?

• How often does your child miss school because he/she is physically tired?

• How often does physical pain make falling asleep at night hard for your child?

• How often does physical pain wake up your child at night?

• How often does your child have physical pain when sitting in a chair or wheelchair?

• How often does your child have physical pain with transfers?

• How often does your child have physical pain when changing positions?

• How often does your child have physical pain when standing?

• How often does your child have physical pain when moving around?

• How often does your child have physical pain when climbing one flight of 8–12 steps?

• How often does your child have physical pain when running?

• For this question, “playing games and sports” means activities that children play with other children such as tag, basketball or bowling. How often does your child have physical pain when playing games or sports?

• How often does your child have physical pain when riding in a car, bus or train?

• How often does your child miss school because of physical pain?

• How often does your child participate in indoor recreational activities without getting physically tired?

• How often is your child physically active?

• How often does your child’s physical pain interfere with wearing his/her braces or splints?

• How often does your child’s physical pain interfere with using his/her adaptive equipment?

• How often does your child drool when sitting quietly?

• How often does your child drool with activity?

• Rating scale: Always; Often; Sometimes; Rarely; Never; Not Applicable