TY - JOUR T1 - “ACPA” in Rheumatoid Arthritis: From Population-based Data to Personalized Medicine JF - The Journal of Rheumatology JO - J Rheumatol SP - 733 LP - 735 DO - 10.3899/jrheum.150281 VL - 42 IS - 5 AU - HENRI A. MÉNARD Y1 - 2015/05/01 UR - http://www.jrheum.org/content/42/5/733.abstract N2 - Rheumatoid arthritis (RA) is a clinical diagnosis, as illustrated by the probabilistic approach adopted in the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria for RA, where diagnosis/classification is based on accumulating a score ≥ 0.61,2. Although that level of probability can be reached using clinical criteria only, when those are insufficient, RA-associated autoantibodies become a determining factor. Proper interpretation of the serology data thus becomes imperative to prevent circular clinical reasoning.The 2010 RA criteria introduced 2 new serology items. First, based on their apparent very high (> 95%) specificity and positive predictive value (PPV) in early and established RA cohorts3, anticitrullinated protein antibodies (“ACPA”) have been added to rheumatoid factor (RF). Second, based on their incremental association with severity and prognosis, antibody titers in both systems, whether absent, low, or high, have been given incremental weight in the scoring system. In the final revision of the ACR/EULAR RA criteria, a detail escaped the attention of the coauthors (including me)1,2. ACPA stands for “anticitrullinated protein antibodies.” Strictly speaking, the ACPA criteria were based exclusively on the anticyclic citrullinated peptide assay (anti-CCP) literature. Hence, the ACPA acronym in the criteria should refer to anticitrullinated peptide/protein antibodies2 depending on which one is used in a particular communication. It is important to emphasize this distinction because ACPA-peptide … Address correspondence to Dr. H.A. Ménard, Division of Rheumatology, McGill University Health Center, 1650 Cedar Ave., Montreal, Québec H3G 1A4, Canada. E-mail: henri.a.menard{at}muhc.mcgill.ca ER -