Clinimetric concepts in outcome assessment: the OMERACT filter.

Validation is the process by which the clinical measurement (clinimetric) properties of an assessment procedure are formally evaluated. In the case of outcome measures, this process traditionally establishes the reliability, validity, and responsiveness of the measurement technique. Although the statistical methods used are diverse, the principles to be followed have been well established and are generally accepted. The basic issues are similar and transcend outcome measurement in different medical conditions. In addition to fulfilling clinimetric requirements, outcome measures are required to be practical in their application. The OMERACT group have recently proposed a novel user-friendly paradigm to capture the essential elements of truth, discrimination, and feasibility. This paradigm is termed the OMERACT filter.