Value of isolated IgA anti-ß2 -glycoprotein I positivity in the diagnosis of the antiphospholipid syndrome.

OBJECTIVE: To examine the prevalence of isolated IgA anti-ß2 -glycoprotein I (anti-ß2 GPI) positivity and the association of these antibodies, and a subgroup that bind specifically to domain IV/V of ß2 GPI, with clinical manifestations of the antiphospholipid syndrome (APS) in 3 patient groups and to evaluate the pathogenicity of IgA anti-ß2 GPI in a mouse model of thrombosis. METHODS: Patients with systemic lupus erythematosus (SLE) from a multiethnic, multicenter cohort (LUpus in MInorities, NAture versus nurture [LUMINA]) (n = 558), patients with SLE from the Hopkins Lupus Cohort (n = 215), and serum samples referred to the Antiphospholipid Standardization Laboratory (APLS) (n = 5,098) were evaluated. IgA anti-ß2 GPI titers and binding to domain IV/V of ß2 GPI were examined by enzyme-linked immunosorbent assay (ELISA). CD1 mice were inoculated with purified IgA anti-ß2 GPI antibodies, and surgical procedures and ELISAs were performed to evaluate thrombus development and tissue factor (TF) activity. RESULTS: A total of 198 patients were found to be positive for IgA anti-ß2 GPI isotype, and 57 patients were positive exclusively for IgA anti-ß2 GPI antibodies. Of these, 13 of 23 patients (56.5%) in the LUMINA cohort, 17 of 17 patients (100%) in the Hopkins cohort, and 10 of 17 patients (58.9%) referred to APLS had at least one APS-related clinical manifestation. Fifty-four percent of all the IgA anti-ß2 GPI-positive serum samples reacted with domain IV/V of anti-ß2 GPI, and 77% of those had clinical features of APS. Isolated IgA anti-ß2 GPI positivity was associated with an increased risk of arterial thrombosis (P < 0.001), venous thrombosis (P = 0.015), and all thrombosis (P < 0.001). The association between isolated IgA anti-ß2 GPI and arterial thrombosis (P = 0.0003) and all thrombosis (P = 0.0003) remained significant after adjusting for other risk factors for thrombosis. In vivo mouse studies demonstrated that IgA anti-ß2 GPI antibodies induced significantly larger thrombi and higher TF levels compared to controls. CONCLUSION: Isolated IgA anti-ß2 GPI-positive titers may identify additional patients with clinical features of APS. Testing for these antibodies when other antiphospholipid tests are negative and APS is suspected is recommended. IgA anti-ß2 GPI antibodies directed to domain IV/V of ß2 GPI represent an important subgroup of clinically relevant antiphospholipids.

Antiphospholipid antibodies and sub-clinical atherosclerosis in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort.

OBJECTIVE AND DESIGN: Antiphospholipid antibodies (APA) have been associated with clinical cardiovascular disease, but it remains unclear whether APA are associated with sub-clinical atherosclerosis. This study examined the relationship between APA and sub-clinical atherosclerosis, measured as coronary artery calcification (CAC), in participants from the prospective Coronary Artery Risk Development in Young Adults (CARDIA) Study. SUBJECTS AND METHOD: 2,203 black and white participants with sera available from the CARDIA year 7 examination and CAC measured by computed tomography at years 15 or 20 were selected. RESULTS: Anti-ß2-glycoprotein I (anti-ß2-GPI) immunoglobulin (Ig) M, IgG, and IgA were positive in 7.0, 1.4, and 1.8 % of participants, respectively; anti-cardiolipin (aCL) IgM and IgG were positive in 1.5 and 1.0 %, respectively. 9.5 % of participants had CAC score >0 at year 15. Anti-ß2-GPI IgM, IgG, IgA, and aCL IgG positivity were associated with CAC >0 at year 15 after adjustment for traditional cardiovascular risk factors; [odds ratios (95 % confidence intervals) were 1.7 (1.0, 3.1), 6.4 (2.4, 16.8), 5.6 (2.3, 13.2), and 5.1 (1.4, 18.6), respectively]. Anti-ß2-GPI IgG was associated with year 20 CAC >0, and anti-ß2-GPI IgA and aCL IgG were marginally associated. CONCLUSIONS: These findings indicate that APA positivity during young adulthood is a risk factor for subsequent sub-clinical atherosclerosis and might play a role in the pathogenesis of atherosclerosis

New classification of the shared epitope in rheumatoid arthritis: impact on the production of various anti-citrullinated protein antibodies.

OBJECTIVE: HLA-DR [shared epitope (SE)] alleles have recently been re-classified into S1, S2, S3P and S3D groups. S2 and S3P have been associated with increased risk for RA. We assessed the impact of S1, S2, S3P and S3D alleles on anti-citrullinated protein antibody (ACPA) production. Instead of comparing allele-carriers to non-carriers, we studied each allele group individually, using the X/X (non-SE) genotype as reference. METHODS: Serum and genomic DNA samples of 91 RA patients and 78 healthy controls were obtained. Various ACPAs and IgM RF were determined by ELISA. HLA-DRB1 genotyping and subtyping was performed by PCR. HLA-DRB1 alleles were re-classified as described above. Correlations between SE and ACPAs were determined. RESULTS: Not only S2 and S3P, but, to a lesser extent, S1 and S3D alleles also predisposed to anti-cyclic citrullinated peptide (CCP) production (P < 0.0001, P = 0.004, P = 0.01 and P = 0.027, respectively), with the following hierarchy of association: S2+S3P > S1+S3D > X/X. Similar associations were observed for anti-citrullinated vimentin. Anti-citrullinated fibrinogen (CF) exerted a different association pattern with the strongest correlation with S1 alleles [odds ratio (OR) 16.00; P = 0.05]. In addition, HLA-DRB1*15 alleles may represent a special predisposing effect for anti-CF antibody production. Finally, in this study, RF production was associated only with the HLA-DRB1*0401 SE allele (P = 0.04). CONCLUSIONS: Our approach of comparing individual S allele carriers with X/X genotype patients allowed us to perform unequivocal analyses and demonstrate new associations. Thus, novel subgroups of RA could be identified with potential relevance for prognosis and therapy.

Myth and reality: practical test system for the measurement of anti-DNA antibodies in the diagnosis of systemic lupus erythematosus (SLE).

The myth persists that only the labor intensive Farr radioimmunoassay and Crithidia luciliae immunofluorescence (CL-IFA) are systemic lupus erythematosus (SLE)-specific tests. We compared them to ELISA with bacteriophage lambda DNA (EL-dsDNA) and denatured calf thymus DNA (EL-ssDNA). By percentile ranking, the specificity cut-off level was set both out of clinical context (SOCC) on 100 blood bank donors, and in clinical context (SICC) on 100 patients with either rheumatoid arthritis or scleroderma (50/50). Clinical sensitivity was calculated on 100 random SLE patients. At 95% SICC, the sensitivity of Farr, CL-IFA, EL-dsDNA, and EL-ssDNA was similar (95%CI): 76% (66-84), 76% (66-84), 63% (53-72), and 75% (65-83), respectively; 87% of the patients were positive by at least one method and 55%by all methods. At 99% SICC, the sensitivity was also similar (95% CI): 57% (47-67), 47% (37-57), 58% (47-67), and 43% (33-53), respectively. The areas under ROC curve were similar (95% CI) when patients were used as controls for specificity. At 99% SOCC, EL-ssDNA identified 89% positive, 2 negative but positive by another method at 95% SICC, and 9 negative (i.e. 89/2/9), followed by CL-IFA (80/6/14), Farr (76/12/12), and EL-dsDNA (64/23/13). Thus, at relatively low cost and easy automation, under the same conditions of specificity, the two ELISA tests combined were at least as good, if not superior, to CL-IFA or Farr: they showed similar clinical sensitivity and also identified more patients with anti-DNA antibodies.

Association of Rheumatoid Factors With Subclinical and Clinical Atherosclerosis in African American Women: The Multiethnic Study of Atherosclerosis.

OBJECTIVE: Although the association between rheumatoid arthritis (RA) and cardiovascular disease (CVD) is established, the exact mechanism is unknown. We tested the hypothesis that RA-related autoantibodies are independent risk factors for subclinical atherosclerosis and subsequent clinical CVD events. METHODS: The Multi-Ethnic Study of Atherosclerosis (MESA) is a community-based cohort study prospectively collecting CVD outcome and risk factor data in middle-aged to elderly multiethnic participants since 2000. Rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP2) by enzyme-linked immunosorbent assay, and coronary artery calcium (CAC) by computed tomography, were measured at MESA baseline in 6,532 participants who were followed for 10.3 years for coronary heart disease (CHD) end points (myocardial infarction, cardiac arrest, CHD death) and CVD end points (included CHD end points, stroke, stroke death). Multivariable logistic regression and Cox regression assessed associations between RF/anti-CCP and CAC or CVD end points. RESULTS: IgM RF, IgA RF, anti-CCP, and either RF isotype predictors were positive in 15.8%, 8.7%, 2.0%, and 20.6%, respectively. A total of 12.2% had CAC ≥300, 7.1% had CHD end points, and 10.2% had CVD end points. IgA RF and anti-CCP were associated with CAC ≥300 in African American women (odds ratio [OR] 2.4 [95% confidence interval (95% CI) 1.2-5.1] and OR 4.1 [95% CI 1.3-12.7], respectively). RA-related autoantibodies were also associated with clinical CVD events in African American women (anti-CCP: OR 5.3 [95% CI 2.4-12.0]; either RF isotype: OR 2.4 [95% CI 1.4-4.0]). There was a trend for association between autoantibodies and CAC in white women. No associations were found in men. CONCLUSION: RA-related autoantibodies are associated with subclinical and clinical atherosclerosis in African American women from a community-based non-RA cohort, indicating autoimmune factors may play a role in the pathogenesis of atherosclerosis.

Relationship between rheumatoid factor isotypes and IgG anti-cyclic citrullinated peptide antibodies.

OBJECTIVE: To validate in a general patient population (GPP) the clinical value of measuring rheumatoid factor (RF) isotypes in relationship to IgG anti-cyclic citrullinated peptide (CCP) antibodies (CCP2 and CCP3). METHODS: Serum samples were obtained as follows: 1021 GPP, for whom RF was ordered for diagnosis, 137 with rheumatoid arthritis (RA), 100 healthy blood donors (HBD), and 50 with systemic lupus erythematosus. Turbidimetry and ELISA were utilized for RF screening, and individual RF isotypes and IgG anti-CCP antibodies were measured by ELISA; RF IgG was measured after pepsin digestion. RESULTS: We validated the generally accepted 90%-98% positive predictive value (PPV) and about 68% sensitivity of the anti-CCP2 test on our diagnosed cohorts as 96% (95% CI 89-99) and 65% (95% CI 56-73), respectively. The 282 RF IgM+ specimens identified in the GPP were subdivided into 3 subsets: (1) 83 as RF IgM+ IgG+ IgA+ with 63% (95% CI 51-73) anti-CCP2+ (i.e., sensitivity similar to the RA cohort); (2) 50 as RF IgM+ IgG- IgA+ with significantly fewer anti-CCP2+ (22%; 95% CI 12-36); and (3) about half as IgM+ IgG- IgA- with just 3% (95% CI 1-8) anti-CCP2+, i.e., not significantly different from the 1% (95% CI 0-5) in HBD. Thus, the chance for a specimen in the GPP to be anti-CCP2+ (i.e., to come from an RA patient) was increased by 7- and 21-fold, respectively, by identifying RF IgA and IgG in addition to IgM. About one-third of anti-CCP- RA patients in our cohort were RF IgM+ IgG+ IgA+, reflected as 3.4% in the anti-CCP2- GPP. The agreement between anti-CCP2 and anti-CCP3 was significantly higher for RF+ RA and GPP patients, 86% (95% CI 78-93) and 83% (95% CI 73-91), respectively, than for the RF- RA (27%; 95% CI 6-61), RF- GPP (4%; 95% CI 0-19), and non-RA controls. Anti-CCP2 but not anti-CCP3 significantly distinguished the HBD from the GPP (95% CI). CONCLUSION: Measurement of the 3 isotypes of RF may increase by 7- to 21-fold the chance of making the serologic diagnosis of RA; a testing algorithm is proposed. The anti-CCP antibody response appears significantly less peptide-specific in the presence of IgM RF than in its absence.

Information on diagnosis and management of systemic lupus erythematosus derived from the routine measurement of 8 nuclear autoantibodies.

OBJECTIVE: To determine the value of routine measurement of a panel of 8 nuclear autoantibodies (ANA/8) for the diagnosis and management of patients with systemic lupus erythematosus (SLE). METHODS: To estimate disease sensitivity of ANA/8, we studied 25 patients with new SLE and 114 with new and established SLE. To estimate disease specificity, 100 patients with other autoimmune rheumatic diseases were included. We used computerized statistical analysis of the level of 8 ANA in relation to clinical activity determined as Systemic Lupus Activity Measure disease activity scores (DAS). Data were collected retrospectively from the charts of 114 patients with 698 visits and evaluated by multiple and piece-wise linear regression analysis (PWLRA) and correlation and cluster analyses. RESULTS: The disease sensitivity of the 3 types of SLE profiles identified was 100% for new SLE patients (n = 25) and 87% for mixed SLE patients; the disease specificity was 98%. Autoantibody levels of anti-ssDNA, dsDNA, and Scl-70 were the best individual correlates of general and organ-specific DAS. Twenty-four percent (R2) of the variability in the general DAS was explained by the multiple regression (R = 0.49), with significant contribution made by anti-Scl-70 (beta = 0.39), dsDNA (beta = 0.17), Sm (beta = 0.10), and SSA (beta = 0.08). PWLRA indicated that for 68% of the 698 clinical presentations (average 6/patient), the observed DAS and the predicted DAS from autoantibody levels were both low and clustered; they were partially discrepant for the remaining 32%, which was explained by the relatively high correlation of DAS with prior changes in autoantibody levels (R = 0.6). The changes in DAS and in anti-dsDNA levels were significantly predicted by the multiple regression at one prior visit, with anti-ssDNA as the main contributor. CONCLUSION: The ANA/8 profile showed ~ 100% sensitivity and ~ 98% specificity for SLE and correlated with contemporary and subsequent changes in DAS and autoantibody levels. Among autoantibodies of this profile, anti-ssDNA (ssDNA) was the most sensitive indicator of SLE and the main contributor to prediction of subsequent changes in DAS.