Protocol of the COSMIN study: COnsensus-based Standards for the selection of health Measurement INstruments

An international Delphi study will be performed to reach consensus on which and how measurement properties should be assessed, and on criteria for good measurement properties. Two sources of input will be used for the Delphi study: (1) a systematic review of properties, standards and criteria of measurement properties found in systematic reviews of measurement instruments, and (2) an additional literature search of methodological articles presenting a comprehensive checklist of standards and criteria. The Delphi study will consist of four (written) Delphi rounds, with approximately 30 expert panel members with different backgrounds in clinical medicine, biostatistics, psychology, and epidemiology. The final checklist will subsequently be field-tested by assessing the inter-rater reproducibility of the checklist.Since the study will mainly be anonymous, problems that are commonly encountered in face-to-face group meetings, such as the dominance of certain persons in the communication process, will be avoided. By performing a Delphi study and involving many experts, the likelihood that the checklist will have sufficient credibility to be accepted and implemented will increase.Choosing the appropriate health status measurement instrument for a specific purpose is a difficult and time-consuming task. The choice depends on the proposed use of the instrument, the concept to be measured, the readability of the questions, the requirements and costs associated with the use of the instrument, the burden on the subjects, and, last but not least, the measurement properties of the instruments. The measurement properties concern internal consistency, reproducibility, content and construct validity, responsiveness, and interpretability. Kirshner and Guyatt distinguished three kinds of health status measures, i.e. discriminative, predictive and evaluative measures [1]. Not all measurement properties are equally important for each purpose. For example, responsiveness is only importa