Differential item functioning in the Patient Reported Outcomes Measurement Information System Pediatric Short Forms...

Area of Science:

• Pediatric Rehabilitation
• Health Outcomes Measurement
• Cerebral Palsy Research

Background:

• Patient-Reported Outcomes Measurement Information System (PROMIS) instruments are widely used to assess health status.
• Cerebral palsy (CP) affects mobility, fatigue, and pain, necessitating accurate outcome measurement.
• Differential item functioning (DIF) can indicate if items function differently across groups, potentially biasing scores.

Purpose of the Study:

• To investigate differential item functioning (DIF) in PROMIS Mobility, Fatigue, and Pain Interference Short Forms (SFs) among children and adolescents with CP.
• To compare item parameter estimates from a CP sample to the original PROMIS calibration sample.

Main Methods:

• Utilized the Graded Response Model to compare item parameter estimates.
• Analyzed data from 303 children and adolescents with CP.
• Employed a two-step item response theory likelihood ratio procedure to detect DIF.

Main Results:

• Significant DIF was found in 4/8 Mobility items, 2/8 Pain Interference items, and 1/10 Fatigue items.
• DIF notably impacted total score estimation for Mobility and Pain Interference, but not Fatigue.
• Identified specific PROMIS scales requiring careful consideration for use in the CP population.

Conclusions:

• Responses to certain PROMIS Mobility and Pain Interference items differ between adolescents with CP and the general population.
• Further investigation, including cognitive interviews, is recommended to understand item interpretation by adolescents with CP.
• Findings may inform the appropriate use and adaptation of PROMIS measures for individuals with CP.