Reappraisal of OMERACT 8 draft validation criteria for a soluble biomarker reflecting structural damage endpoints in rheumatoid arthritis, psoriatic arthritis, and spondyloarthritis: the OMERACT 9 v2 criteria.

Objectives: A draft set of criteria for the validation of soluble biomarkers reflecting damage endpoints was proposed at OMERACT 8. At OMERACT 9 we aimed to scrutinize the necessity for each of these criteria according to the objectives of the working group.

Methods: The OMERACT 8 draft criteria and the principle objectives of the validation process were clarified at a meeting of the working group in London, December 2007. A new framework was proposed after the following steps were conducted: (A) A systematic review of the literature focusing on the draft criteria and a preselected group of biomarkers (MMP3, CTX-II, RANKL, OPG, CTX-I) followed by a Delphi consensus exercise addressing the importance of individual criteria and identification of omissions in the draft set. (B) Formal debate as well as group discussion centered on the key arguments for inclusion/exclusion of specific criteria. (C) Onsite interactive electronic voting on the importance of specific criteria. The framework was presented and discussed at OMERACT 9 in both breakout and plenary sessions followed by a vote on its acceptance.

Results: The objectives of rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis biomarkers in relation to their predictive validity for damage endpoints was clarified and supported by OMERACT 9 participants. The OMERACT 8 draft validation criteria were reformulated into an essential category focused on criteria addressing the OMERACT Filter elements of discrimination (incorporating truth) and feasibility, and a desirable but nonessential category of other criteria addressing truth. This revised draft set was endorsed by participants at OMERACT 9.

Conclusion: A revised set of validation criteria has been drafted by consensus at OMERACT 9 that focuses on the performance characteristics of biomarker assays, the importance of addressing potential confounders, and the essential requirement for clinical validation studies.