Although relationships between biomarkers and various disease activity measures were assessed during the development process, the DAS28-CRP was chosen as the reference for final algorithm training because of its established validation against the DAS28-ESR [6], a disease activity measure shown to predict RA outcomes in clinical trials [49], and because measurement of CRP is more readily standardized than ESR in banked samples from multiple studies and sites. The gene discussed is CRP; the disease is rheumatoid arthritis.