Estimating a Preference-Based Index from the Clinical Outcomes in Routine Evaluation–Outcome Measure (CORE-OM): Valuation of CORE-6D

tion–Outcome Measure (CORE-OM) is used to evaluate the effectiveness of psychological therapies in people with common mental disorders. The objective of this study was to estimate a preference-based index for this popula-tion using CORE-6D, a health state classification system derived from the CORE-OM consisting of a 5-item emo-tional component and a physical item, and to demonstrate a novel method for generating states that are not orthogo-nal.Methods. Rasch analysis was used to identify 11 emo-tional health states from CORE-6D that were frequently observed in the study population and are, thus, plausible (in contrast, conventional statistical design might generate implausible states). Combined with the 3 response levels of the physical item of CORE-6D, they generate 33 plausi-ble health states, 18 of which were selected for valuation