Purpose: To evaluate the equivalence of the PROMIS® wave 1 physical functioning item bank, by age (50 years
or older versus 18-49).
Materials and methods: A total of 114 physical functioning items with 5 response choices were administered to English- (n=1504) and Spanish-language (n=640) adults. Item frequencies, means and standard deviations, itemscale correlations, and internal consistency reliability were estimated. Differential Item Functioning (DIF) by age was evaluated.
Results: Thirty of the 114 items were flagged for DIF based on an R-squared of 0.02 or above criterion. The
expected total score was higher for those respondents who were 18-49 than those who were 50 or older.
Conclusions: Those who were 50 years or older versus 18-49 years old with the same level of physical functioning responded differently to 30 of the 114 items in the PROMIS® physical functioning item bank. This study yields essential information about the equivalence of the physical functioning items in older versus younger individuals.
Author: Paz, S. H., Spritzer, K. L., Morales, L. S., & Hays, R. D. (2013).
Source: Primary Health Care, 3, 131.https://www.iomcworld.org/open-access/age-related-differential-item-functioning-for-the-patient-reported-outcomes-information-system-(promise)-physical-functioning-items-2167-1079.1000131.pdf