Differential Item Function Analysis of a Scale Measuring Worry About Affording Healthcare in Multiple Sclerosis

Purpose/objective: A measure of worry about affording health care was developed in people with multiple sclerosis (MS) to further the study of how trouble affording health care can affect health. This study examined whether the measure showed bias by gender, age, insurance type, income, and type of MS. Absence of bias would facilitate comparisons between groups in future studies. Research methods/Design: A sample of 433 people with MS completed the 5-item worry about affording health care measure. Demographic information was also collected. To test for bias, we used differential item function analysis with the graded response model of item response theory. We tested for bias from gender, age, insurance type, income, and type of MS.

Results: Differential item function analyses found no significant bias for the worry about affording health care measure when comparing the following groups: men to women; younger than 55 years old to 55 years and older; public insurance to no public insurance; lower income to higher income; and relapsing/remitting MS type to other MS types.

Conclusions/implications: This brief measure of worry about affording health care can be used in future studies without concern for measurement bias on the factors examined here. Future studies should examine the relationship of this worry to adherence to treatment and other factors that may be affected by worries about health care affordability. (PsycINFO Database Record