Differential item functioning by language on the PROMIS^® physical functioning items for children and adolescents

Area of Science:

• Health Outcomes Research
• Pediatric Health Measurement
• Psychometrics

Background:

• Accurate assessment of physical functioning in children is crucial for evaluating health and guiding interventions.
• The Patient-Reported Outcomes Measurement Information System (PROMIS) offers validated item banks for measuring health status.
• Ensuring cross-language equivalence is vital for equitable application of PROMIS in diverse populations.

Purpose of the Study:

• To evaluate the measurement equivalence of the PROMIS pediatric physical functioning item banks between English and Spanish language versions.
• To determine if self-reports of physical functioning are comparable across linguistic groups in pediatric populations.

Main Methods:

• Utilized large samples of pediatric respondents (N=5091 English, N=605 Spanish) for the PROMIS physical functioning item banks.
• Employed differential item functioning (DIF) analyses to identify items that function differently across language groups.
• Calculated product-moment correlations between scores derived from English and equated Spanish item parameters.

Main Results:

• Differential item functioning (DIF) was identified for 4 upper extremity and 7 mobility items between English and Spanish versions.
• High correlations (0.98 for upper extremity, 0.99 for mobility) were observed between scores using equated parameters.
• Excluding participants with misfit slightly altered DIF results, indicating robustness of the core findings.

Conclusions:

• The PROMIS pediatric physical functioning item banks demonstrate measurement equivalence across English and Spanish language versions.
• Findings support the reliable use of these PROMIS tools for assessing physical functioning in diverse pediatric populations.
• Further research is recommended to replicate these findings in additional samples.