The Turkish Multiple Sclerosis Walking Scale (MSWS-12v2T): Is It the Same Measure as the Original Version? (P3.136)

OBJECTIVE: Here, we develop a Turkish version of the MSWS-12v2, test its measurement properties, and its measurement equivalence compared with the original English version. BACKGROUND: International clinical trials require patient-reported rating scales to be available in many languages that ensure cross-cultural measurement equivalence. This is a stringent requirement. DESIGN/METHODS: A recommended approach generated the Turkish version (MSWS-12v2T): a panel of bi-lingual people performed forward ( English to Turkish) and backward (Turkish to English) translations, and resolved discrepancies. A two-stage psychometric evaluation followed: standard Rasch measurement theory analysis of data from 127 Turkish people with MS ; examination of item performance equivalence across Turkish and English (n=150) people (differential item functioning, DIF). RESULTS: Rasch measurement theory analyses supported MSWS-12v2T’s reliability and validity. However, compared with the original English MSWs-12v2, 8 items had significant DIF implying cross-cultural differences in item perception. Items were removed, sequentially in DIF magnitude order, to determine whether item DIF was real or compensatory. DIF was not detected after four items were removed. CONCLUSIONS: Although MSWS-12v2T appears reliable and valid there were cultural differences in people’s responses to four items (standing, stairs, balance, walking). Whilst post hoc analyses can “correct for” these differences to ensure measurement equivalence, qualitative research is required to explain why Turkish people perceive these four tasks as more difficult. Importantly, findings indicate the standard approach to producing “valid”scale translations - forward and backward translation to achieve linguistic equivalence - doesn’t guarantee measurement equivalence. This could undermine inferences from international clinical trials. Study Supported by: Gen Pharmaceuticals Disclosure: Dr. Dib has received personal compensation for activities with Gen Pharmaceuticals as an employee. Dr. Dib has received research support from Gen Pharmaceuticals. Dr. Tamam has nothing to disclose. Dr. Terzi has nothing to disclose. Dr. Hobart has received personal compensation for activities with Acorda Therapeutics, Bayer Schering, Biogen Idec, Merck Serono, Novartis, and Teva Neuroscience. Dr. Hobart has received research support from Biogen Idec, Novartis, and Merck Serono.