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Objective To evaluate the diagnostic accuracy of anticarbamylated protein antibodies (CarP), alone and in combination with traditional biomarkers (rheumatoid factor [RF] and anticitrullinated peptide antibodies [ACPA]), in established rheumatoid arthritis (RA). Methods A commercially available enzyme‐linked immunosorbent assay (ELISA) kit was used to assess CarP concentrations in serum samples of 200 established RA and 206 controls (115 healthy donors and 55 patients with other rheumatic diseases). Main outcome measures were sensitivity, specificity, and area under the curve (AUC; 95% confidence interval [CI]). Difference in accuracy was evaluated by comparison of the respective AUCs. Results A serum CarP cut‐off of 1.47 ng/ml or more differentiated patients with RA from controls with 30% sensitivity, 97.1% specificity, and good accuracy (AUC[95%CI] = 0.83[0.79‐0.86], P < 0.0001). However, it showed moderate diagnostic accuracy in seronegative RA patients: sensitivity 17.9%, specificity 96.9%, and AUC (95% CI) = 0.69 (0.63‐0.75). The diagnostic accuracy of CarP_ACPA and CarP_RF combinations was significantly superior to that of ACPA and RF alone (P < 0.0001 and P = 0.015, respectively), but not to that of ACPA_RF combination (P = 0.089) In addition, the CarP_ACPA_RF combination did not improve the diagnostic accuracy of the ACPA_RF combination (AUC mean difference [95% CI] = 0.006 [−0.001 to 0.015], P = 0.10). The number of positive autoantibodies (0, 1, 2, or 3) was not significantly associated with moderate‐severe disease (Disease Activity Score‐28 [DAS‐28] > 3.2) in adjusted multiple regression analysis. Conclusion CarP has good diagnostic accuracy in established RA but not in seronegative RA. The addition of CarP to ACPA and RF alone or in combination does not significantly enhance the diagnostic accuracy of ACPA_RF combination.

A capillary electrophoresis method was developed to detect and measure hydroxychloroquine (HCQ) and its active metabolite desethyl hydroxychloroquine (DHCQ) in whole blood in patients with rheumatoid arthritis. The best separation in terms of peak area reproducibility, migration time, peak shape, and resolution of adjacent peaks was obtained in a 60 cm, 75 µm i.d. uncoated fused-silica capillary using a background electrolyte mixture of an aqueous 55 mmol/L TRIS solution brought to pH 2.6 with phosphoric acid and methanol (85:15) and a voltage and a temperature of separation of 20 kV and 30 °C, respectively. Analytes were separated in less than 12 min, with excellent linearity (R 2 ≥ 0.999) in the concentration range of 0.5-8 µmol/L. The recovery of analytes spiked in whole blood was 99-101% for HCQ and 98-99% for DHCQ. Analysis of five samples from patients with rheumatoid arthritis receiving HCQ 400 mg daily yielded mean steady-state concentrations of 2.27 ± 1.61 and 1.54 ± 0.55 μmol/L for HCQ and DHCQ, respectively, with a HCQ to DHCQ ratio of 1.40 ± 0.77.

Objective: To evaluate the diagnostic accuracy of anticarbamylated protein antibodies (CarP), alone and in combination with traditional biomarkers (rheumatoid factor [RF] and anticitrullinated peptide antibodies [ACPA]), in established rheumatoid arthritis (RA)., Methods: A commercially available enzyme-linked immunosorbent assay (ELISA) kit was used to assess CarP concentrations in serum samples of 200 established RA and 206 controls (115 healthy donors and 55 patients with other rheumatic diseases). Main outcome measures were sensitivity, specificity, and area under the curve (AUC; 95% confidence interval [CI]). Difference in accuracy was evaluated by comparison of the respective AUCs., Results: A serum CarP cut-off of 1.47 ng/ml or more differentiated patients with RA from controls with 30% sensitivity, 97.1% specificity, and good accuracy (AUC[95%CI] = 0.83[0.79-0.86], P < 0.0001). However, it showed moderate diagnostic accuracy in seronegative RA patients: sensitivity 17.9%, specificity 96.9%, and AUC (95% CI) = 0.69 (0.63-0.75). The diagnostic accuracy of CarP&#95;ACPA and CarP&#95;RF combinations was significantly superior to that of ACPA and RF alone ( P < 0.0001 and P = 0.015, respectively), but not to that of ACPA&#95;RF combination ( P = 0.089) In addition, the CarP&#95;ACPA&#95;RF combination did not improve the diagnostic accuracy of the ACPA&#95;RF combination (AUC mean difference [95% CI] = 0.006 [-0.001 to 0.015], P = 0.10). The number of positive autoantibodies (0, 1, 2, or 3) was not significantly associated with moderate-severe disease (Disease Activity Score-28 [DAS-28] > 3.2) in adjusted multiple regression analysis., Conclusion: CarP has good diagnostic accuracy in established RA but not in seronegative RA. The addition of CarP to ACPA and RF alone or in combination does not significantly enhance the diagnostic accuracy of ACPA&#95;RF combination., (© 2019, The Authors. ACR Open Rheumatology published by Wiley Periodicals, Inc. on behalf of American College of Rheumatology.)

Endogenous retroviruses (HERV) are believed to be pathogenic in several autoimmune diseases. Among them, HERV-K viruses have been reported recently to be involved in the pathogenesis of rheumatoid arthritis (RA). In this study we have explored the role of humoral immune response against HERV-K as a potential pathogenetic mechanism in RA. Four different peptides from the extracellular portion of the env protein of HERV-K (env-su 19-37 , env-su 109-126 , env-su 164-186 , env-su 209-226 ) were selected by bioinformatic analysis on the basis of their putative immunogenicity. Indirect enzyme-linked immunosorbent assay (ELISA) was then carried out to quantify antibodies against those peptides on blood samples of 70 consecutive RA patients and 71 healthy controls (HC). Differences between the two groups were analysed using the Mann-Whitney test. Potential correlations between RA laboratory, clinical descriptors and immunoglobulin (Ig)G levels were explored by bivariate regression analysis. Serum autoantibodies against one of four tested peptides of HERV-K (env-su 19-37 ) were significantly higher in RA than in HC (19 versus 3%, P = 0·0025). Subgroup analysis showed no association between anti-HERV-K peptide humoral response and clinical, serological and clinimetric RA disease descriptors. Serum from RA patients in our series reacted significantly against HERV-K env-su 19-37 peptide in comparison to the general population suggesting a role for the HERV-K- related, secondary antigenic-driven immune response in the pathogenesis of RA. Further studies are needed to confirm these results and to explore the role of this HERV-K surface peptide as a potential therapeutic target., (© 2017 British Society for Immunology.)

Objective: To investigate whether levels of asymmetric dimethylarginine (ADMA), as a measure of endothelial dysfunction, are higher in patients with rheumatoid arthritis compared with healthy control subjects. The relationships between ADMA and surrogate measures of arterial stiffness were evaluated., Methods: Patients with rheumatoid arthritis and healthy control subjects were recruited. ADMA was quantified via enzyme-linked immunosorbent assay. Arterial stiffness was evaluated using pulse wave analysis., Results: There was no significant difference in plasma ADMA concentration between patients with rheumatoid arthritis (n = 30) and healthy controls (n = 30). Aortic augmentation pressure was significantly higher in patients than in controls. C-reactive protein and Health Assessment Questionnaire score were independent predictors of arterial stiffness in patients. There was no relationship between ADMA concentration and aortic augmentation pressure in the study population as a whole., Conclusions: Arterial stiffness appears to be increased in rheumatoid arthritis and independently associated with systemic inflammation and physical disability. ADMA concentration was not increased in this small group of patients with rheumatoid arthritis compared with healthy controls; nor was it associated with arterial stiffness., (© The Author(s) 2016.)