Fig. 3

Multiplex positivity in anti-CCP-2-negative RA patients is not RA-specific. a Percentage of anti-CCP-2-negative RA patients (n = 279) in the EAC who are positive (n = 86) or negative (n = 193) in the multiplex array. b Pie diagram summarizes the percentage of multiplex-positive (n = 37, grey) and -negative (n = 98, white) anti-CCP-2-negative non-RA/UA patients (n = 135). Bar diagram plots the number of patients who are multiplex-positive and -negative with different diagnoses. c-d ACR 1987 criteria were used to calculate the sensitivity and specificity for RA of the anti-CCP-2 test (c) and of the multiplex array (d) by comparing patients who fulfilled the ACR 1987 criteria with patients who did not (UA patients or patients with a different form of arthritis). ACR American College of Rheumatology, CCP cyclic citrullinated peptide, EAC Leiden Early Arthritis Clinic, LR likelihood ratio, MCTD mixed connective-tissue disease, RA rheumatoid arthritis, UA undifferentiated arthritis