Differential item functioning in the Patient Reported Outcomes Measurement Information System Pediatric Short Forms in a sample of children and adolescents with cerebral palsy.
OBJECTIVE
The present study examined the Patient Reported Outcomes Measurement Information System (PROMIS) Mobility, Fatigue, and Pain Interference Short Forms (SFs) in children and adolescents with cerebral palsy (CP) for the presence of differential item functioning (DIF) relative to the original calibration sample.


METHODS
Using the Graded Response Model we compared item parameter estimates generated from a sample of 303 children and adolescents with CP (175 males, 128 females; mean age 15y 5mo) to parameter estimates from the PROMIS calibration sample, which served as the reference group. DIF was assessed in a two-step process using the item response theory-likelihood ratio-differential item functioning detection procedure.


RESULTS
Significant DIF was identified for four of eight items in the PROMIS Mobility SF, for two of eight items in the Pain Interference Scale, and for one item out of 10 on the Fatigue Scale. Impact of DIF on total score estimation was notable for Mobility and Pain Interference, but not for Fatigue.


CONCLUSIONS
Results suggest differences in the responses of adolescents with CP to some items on the PROMIS Mobility and Pain Interference SFs. Cognitive interviews about the PROMIS items with adolescents with varying degrees of mobility limitations would provide better understanding of how they are interpreting and selecting responses to the PROMIS items and thus help guide selection of the most appropriate way to address this issue.
Department of Occupational Therapy, Boston University College of Health and Rehabilitation Sciences: Sargent College, Boston, MA, USA. wjcoster@bu.edu.
Wendy J
WJ
Coster
Health and Disability Research Institute, Boston University School of Public Health, Boston, MA, USA.
Pengsheng
P
Ni
Health and Disability Research Institute, Boston University School of Public Health, Boston, MA, USA.
Mary D
MD
Slavin
Department of Physical Therapy, College of Health Sciences, University of Delaware, Newark, DE, USA.
Pamela A
PA
Kisala
College of Education and Human Development, University of Delaware, Newark, DE, USA.
Ratna
R
Nandakumar
Department of Occupational Therapy, Thomas Jefferson University, Philadelphia, PA, USA.
Mary Jane
MJ
Mulcahey
Department of Physical Therapy, College of Health Sciences, University of Delaware, Newark, DE, USA.|Kessler Foundation Research Center, West Orange, NJ, USA.
David S
DS
Tulsky
Health and Disability Research Institute, Boston University School of Public Health, Boston, MA, USA.
Alan M
AM
Jette
D000293:Adolescent; D002547:Cerebral Palsy / Q000150:complications*; D002648:Child; D005221:Fatigue / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008491:Medical Informatics Applications; D051346:Mobility Limitation; D017063:Outcome Assessment, Health Care / Q000379:methods / Q000592:standards*; D010146:Pain / Q000209:etiology*; D000071066:Patient Reported Outcome Measures; D010372:Pediatrics; D011594:Psychometrics / Q000295:instrumentation