Testing patient-reported outcome measurement equivalence in multinational clinical trials: An exemplar using the 12-item Multiple Sclerosis Walking Scale:

BackgroundAlthough multinational clinical trials frequently use patient-reported outcomes to measure efficacy, measurement equivalence across cultures and languages, a scientific requirement, is rarely tested. Clinically accessible accounts are rare; exemplars are needed.ObjectiveTo develop and test a Turkish version of the Multiple Sclerosis Walking Scale (MSWS-12v2) as a clinical exemplar for examining measurement equivalence.MethodsThe MSWS-12v2 Turkish (MSWS-12v2T) was developed using recognised methods for linguistic equivalence. Rasch measurement theory was used to examine measurement performance (multiple tests of targeting, scale performance, and person measurement) and measurement equivalence (differential item functioning). UK data (n = 3310) were used for comparisons and differential item functioning testing.ResultsOne hundred and twenty-four people from two Turkish centres completed the MSWS-12v2T. Rasch measurement theory evidence supported MSWS-12v2T as reliable (person separation = 0.96) an...