Integration of patient and provider assessments of mobility and self-care resulted in unidimensional item-response theory scales

ObjectiveThe objective of this study was to develop a questionnaire that could integrate patient and provider items on mobility and self-care into unidimensional scales. The instrument should be suitable for various measurement models (patient and provider data PAT–PRO], only patient data PAT], only provider data PRO]).Study Design and SettingThe existing instruments, MOSES-Patient and MOSES-Provider, were integrated into the MOSES-Combi and completed by a total of 1,019 neurology, cardiac, or musculoskeletal patients and/or their physicians (MOSES = acronym for “mobilty and self-care”).ResultsAfter selection of 18 items, all 12 scales of the MOSES-Combi (87 items) were largely unidimensional, met the standards for a 1-parameter item-response theory (IRT) model, were sufficiently reliable, and showed no differential item functioning (DIF) for age or gender. The person parameters set in the PAT–PRO measurement model show at least moderate, but usually substantial, agreement with those set in the PRO and PAT measurement models.ConclusionThe advantages of the MOSES-Combi are that it can be used for various measurement models and is suitable for studying agreement between patient and provider assessments because of its psychometric properties (same scaling for patient and provider items). Integration of various data sources in an IRT scale can be extended to other assessments.