Rheumatoid arthritis (RA) is a prototypical autoimmune arthritis affecting nearly 1% of the world population and is a significant cause of worldwide disability. Though prior studies have demonstrated the appearance of RA-related autoantibodies years before the onset of clinical RA, the pattern of immunologic events preceding the development of RA remains unclear. To characterize the evolution of the autoantibody response in the preclinical phase of RA, we used a novel multiplex autoantigen array to evaluate development of the anti-citrullinated protein antibodies (ACPA) and to determine if epitope spread correlates with rise in serum cytokines and imminent onset of clinical RA. To do so, we utilized a cohort of 81 patients with clinical RA for whom stored serum was available from 1–12 years prior to disease onset. We evaluated the accumulation of ACPA subtypes over time and correlated this accumulation with elevations in serum cytokines. We then used logistic regression to identify a profile of biomarkers which predicts the imminent onset of clinical RA (defined as within 2 years of testing). We observed a time-dependent expansion of ACPA specificity with the number of ACPA subtypes. At the earliest timepoints, we found autoantibodies targeting several innate immune ligands including citrullinated histones, fibrinogen, and biglycan, thus providing insights into the earliest autoantigen targets and potential mechanisms underlying the onset and development of autoimmunity in RA. Additionally, expansion of the ACPA response strongly predicted elevations in many inflammatory cytokines including TNF-α, IL-6, IL-12p70, and IFN-γ. Thus, we observe that the preclinical phase of RA is characterized by an accumulation of multiple autoantibody specificities reflecting the process of epitope spread. Epitope expansion is closely correlated with the appearance of preclinical inflammation, and we identify a biomarker profile including autoantibodies and cytokines which predicts the imminent onset of clinical arthritis.

Objective. To evaluate levels of biomarkers in preclinical rheumatoid arthritis (RA) and to use elevated biomarkers to develop a model for the prediction of time to future diagnosis of seropositive RA.Methods. Stored samples obtained from 73 military cases with seropositive RA prior to RA diagnosis and from controls (mean 2.9 samples per case; samples collected a mean of 6.6 years prior to diagnosis) were tested for rheumatoid factor (RF) isotypes, anti-cyclic citrullinated peptide (anti-CCP) antibodies, 14 cytokines and chemokines (by bead-based assay), and C-reactive protein (CRP).Results. Preclinical positivity for anti-CCP and/or >2 RF isotypes was >96% specific for future RA. In preclinical RA, levels of the following were positive in a significantly greater proportion of RA cases versus controls: interleukin-1␣ (IL-1␣), IL-1␤, IL-6, IL-10, IL-12p40, IL-12p70, IL-15, fibroblast growth factor 2, flt-3 ligand, tumor necrosis factor ␣, interferon-␥-inducible 10-kd protein, granulocyte-macrophage colony-stimulating factor, and CRP. Also, increasing numbers of elevated cytokines/chemokines were present in cases nearer to the time of diagnosis. RA patients who were >40 years old at diagnosis had a higher proportion of samples positive for cytokines/chemokines 5-10 years prior to diagnosis than did patients who were <40 years old at diagnosis (P < 0.01). In regression modeling using only case samples positive for autoantibodies highly specific for future RA, increasing numbers of cytokines/chemokines were predictive of decreased time to diagnosis, and the predicted time to diagnosis based on cytokines/chemokines was longer in older compared with younger cases.Conclusion. Levels of autoantibodies, cytokines/ chemokines, and CRP are elevated in the preclinical period of RA development. In preclinical autoantibodypositive cases, the number of elevated cytokines/ chemokines is predictive of the time of diagnosis of future RA in an age-dependent manner.Multiple studies have demonstrated that levels of disease-related biomarkers may be elevated prior to the onset of symptomatic rheumatoid arthritis (RA). These biomarkers include rheumatoid factor (RF) and antibodies to citrullinated protein antigens, as well as secre-

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Objective Anti-carbamylated protein (anti-CarP) antibodies could further elucidate early RA pathogenesis and predict clinical disease. We compared diagnostic accuracy of anti-CarP antibodies for future RA to other RA-related antibodies in military personnel. Methods Stored pre-RA diagnosis serum samples from 76 RA cases were tested for anti-CarP Fetal Calf Serum (FCS), anti-CarP Fibrinogen (Fib), anti-CCP2, RF-Neph, and RF-isotypes (IgM, IgG, and IgA). Positivity for all antibodies was determined as ≥2SD of log-transformed means from controls. Relationships between autoantibodies and future RA were assessed in prediagnosis serum for all RA cases compared to controls using sensitivity, specificity, and logistic regression. Differences in diagnostic accuracy between antibody combinations were assessed using comparisons of area under the curves (AUCs). Results Anti-CarP-FCS was 26% sensitive and 95% specific for future RA, where anti-CarP-Fib was 16% sensitive and 95% specific for future RA. Anti-CarP-FCS positivity was associated with future RA, while anti-CarP-Fib trended towards association. The antibody combination of anti-CCP2 and/or ≥2 RFs (RF-Neph and/or RF-isotypes) resulted in an AUC of 0.72 for future RA, where the AUC was 0.71 with the addition of anti-CarP-FCS to this prior combination. Conclusion Adding anti-CarP-FCS to antibody combinations did not improve AUC. However, anti-CarP-FCS was associated with future onset of RA, and was present in prediagnosis serum in ~10% of RA cases negative for anti-CCP2, but positive for RF.

Objective To compare commonly-available tests for antibodies to citrullinated protein antigens (ACPAs) for diagnostic accuracy and assay agreement in established rheumatoid arthritis (RA) and subjects at elevated risk for RA. Methods ELISA testing for anti-cyclic citrullinated peptide (anti-CCP) antibodies was performed using CCP2 (Axis-Shield) and CCP3.1 (IgA/IgG INOVA) in the following subjects: 1) probands with established RA (N=340) from the Studies of the Etiology of RA (SERA), 2) first degree relatives (FDRs) without RA (family members of SERA RA probands; N=681), 3) Department of Defense Serum Repository (DoDSR) RA cases with pre-diagnosis samples (N=83; 47/83 also had post-diagnosis samples), and 4) blood-donor and DoDSR controls (N=283). Results In established RA, CCP2 was more specific (99.2% vs. 93.1%, p<0.01), but less sensitive (58.7% vs. 67.4%, p=0.01) than CCP3.1, with specificity of CCP3.1 increasing to 97.2% if levels ≥3 times the standard cut-off level were considered. In all subjects, at standard cut-off levels, CCP3.1 positivity was more prevalent. In DoDSR cases, CCP2 was more specific than CCP3.1 for a future diagnosis of RA, and higher CCP levels trended towards greater specificity for disease onset within 2 years. At standard cut-off levels, assay agreement was good in established RA (kappa=0.76), but poor in FDRs without inflammatory arthritis (kappa=0.25). Conclusion Anti-CCP assays differ to an extent that may be meaningful in diagnosing RA in patients with inflammatory arthritis, and in evaluating the natural history of RA development in subjects at-risk for future RA. Mechanisms underlying these differences in test performance need further investigation.

As the rheumatology field is moving toward very early identification of RA and possible screening for individuals at maximum risk of RA in populations with a low pretest probability, an autoantibody profile of triple positivity for ACPAs, RF, and anti-CarP provides interesting information that might help identify individuals at risk of developing RA.

Objective To evaluate patterns of elevations of isotypes of rheumatoid factor (RF) and anti–citrullinated protein antibodies (ACPAs) pre–rheumatoid arthritis (RA) diagnosis and post–RA diagnosis. Methods Using the Department of Defense Serum Repository we identified 214 RA cases and 210 matched controls. Up to 3 pre–RA diagnosis and 1 post–RA diagnosis serum samples per subject were tested for RF and for IgA, IgG, and IgM ACPAs. The timing and trajectories of elevations of autoantibodies were evaluated. Results Autoantibody levels were elevated in cases versus controls a mean of 17.9 years before RA diagnosis for IgG ACPA, 14.2 years for IgA‐RF, 7.2 years for IgM‐RF, 6.2 years for IgA ACPA, and 5.0 years for both IgM ACPA and IgG‐RF (P < 0.01 for all comparisons). There were similar relationships for positive or negative autoantibody status, with cases first showing positivity for IgG ACPA 1.9 years pre‐RA and for IgA‐RF 1.7 years pre‐RA, followed by the other isotypes. Only IgA ACPA positivity was significantly increased in post–RA diagnosis samples (19% 0–2 years pre‐RA versus 39% >2 years post–RA diagnosis; P = 0.04). All autoantibody levels demonstrated an early initial elevation, a period of stability, then an increase immediately before RA diagnosis. A pre‐RA endotype of early elevation of autoantibodies was associated with increased use of biologic therapy, and a higher prevalence of sicca symptoms and lung disease post–RA diagnosis. Conclusion Differences in patterns of elevations of autoantibody isotypes have implications for understanding the pathophysiology of RA development. These include understanding what factors drive initial autoantibody elevations compared to what factors (including mucosal) drive later increases in autoantibody levels and a transition to clinically apparent RA, and how pre‐RA endotypes may influence post–RA diagnosis phenotypes.

Objective To examine serum autoantibodies to malondialdehyde–acetaldehyde (MAA) prior to rheumatoid arthritis (RA) diagnosis. Methods Concentrations of anti‐MAA antibody isotypes, anti–cyclic citrullinated peptide 2 (anti–CCP‐2), and IgM rheumatoid factor (IgM‐RF) were evaluated before and after RA diagnosis in samples from cases (n = 214) and controls (n = 210). The timing of elevations in autoantibody concentrations relative to RA diagnosis was explored using separate mixed models for each antibody and/or isotype. Associations between prediagnosis autoantibody concentrations in RA patients were examined using mixed effects linear regression models. Results Concentrations of IgG (log2 difference 0.34) and IgA (log2 difference 0.43) anti‐MAA antibodies in RA patients diverged from controls at 3.0 years and 2.3 years prior to diagnosis, respectively (P < 0.05 for both). There was no evidence of case–control divergence for IgM anti‐MAA antibody concentration. Anti–CCP‐2 and IgM‐RF concentrations diverged between RA patients and controls beginning at 17.6 years and 7.2 years prior to RA diagnosis, respectively. All 3 anti‐MAA antibody isotypes (IgA, IgM, and IgG) were significantly associated with anti–CCP‐2 antibody and RF concentrations prior to diagnosis (β = 0.22–0.27 for IgM‐RF; β = 0.44–0.93 for anti–CCP‐2) (P < 0.001). Conclusion IgG and IgA anti‐MAA autoantibodies are elevated prior to RA diagnosis but appear later in the preclinical course than anti–CCP‐2 or RF. These findings suggest that MAA formation and anti‐MAA immune responses could play a role in the transition from subclinical autoimmunity to clinically apparent arthritis.