Detection and identification of antinuclear antibodies (ANA) in a large and consecutive cohort of serum samples referred for ANA testing

Prevalence of disease-specific antinuclear antibodies in general population: estimates from annual physical examinations of residents of a small town over a 5-year period

The aim of this study was to investigate the types and prevalence of disease-specific antinuclear antibodies (ANAs) and their relationship to rheumatic diseases in the general Japanese population. An immunofluorescence (IF) method was used for the first screening of ANA levels in serum samples obtained from 2181 residents of a small Japanese town. Individuals positive for IF-ANA were then further tested for disease-specific ANAs using eight enzyme immunoassays. Physical status and the presence of illness were determined by means of questionnaires and medical examinations. Based on the result of the IF-ANA assay, the rates of positive samples at 1:40 and 1:160 dilutions were 26.0 and 9.5%, respectively, with females have significantly higher positivity rates than males (P < 0.0001). Among 566 IF-ANA-positive individuals, 100 individuals were found to have 114 disease-specific ANAs. Anti-SSA/Ro, anti-centromere, and anti-U1RNP antibodies were detected in 58, 30, and 11 individuals, respectively, but anti-Sm, anti-Scl-70, and anti-Jo-1 antibodies were undetectable. Questionnaires and medical examinations revealed that among 60 disease-specific ANA-positive individuals that were available for testing, six had Sjögren's syndrome (SS), five were suspected of having SS, and five had rheumatoid arthritis. Surprisingly, 34 (57%) of the disease-specific ANA-positive individuals were clinically healthy. Anti-SSA/Ro, anti-centromere, and anti-U1RNP antibodies were quite frequent among clinically healthy Japanese subjects, although anti-Sm, anti-Scl-70, and anti-Jo-1 antibodies were not. Of the 60 individuals who tested positive for disease-specific ANAs, 30% (18/60) actually manifested systemic rheumatic diseases, while 50% showed no detectable signs or symptoms of rheumatic diseases.

The management of the patient with unexpected autoantibody positivity

Different autoantibodies are often measured simultaneously; this typically occurs when using indirect immunofluorescence on tissue sections or multiplex detection systems and may generate clinically "unexpected" positivities (i.e., without any relation to the disease under investigation). Their number is expected to increase with the development of microarray systems in autoantibody assays. In general, when examining patients with such unexpected findings, it is necessary to take into account that: a) autoantibody positivities are much more frequent than autoimmune diseases; b) the positive predictive value of an autoantibody positivity depends upon the diagnostic accuracy of the test and disease prevalence; c) autoantibodies may be risk factors for autoimmune disease or may also have a pathogenetic role by themselves. In this article we will highlight the possible problems raised by some relatively common situations, related to anti-nuclear, anti-thyroid, anti-phospholipid and anti-tissue transglutaminase autoantibodies. The need for specific strategies is outlined.

Analytical performance of the AtheNA MultiLyte® ANA II assay in sera from lupus patients with multiple positive ANAs

The purpose of this study was to evaluate the precision and accuracy of a commercial multiplexed kit for the measurement of 9 anti-nuclear antibodies (ANAs; anti-SS/A, anti-SS/B, anti-Sm, anti-RNP, anti-Jo-1, anti-Scl-70, anti-dsDNA, anti-Centromere B, and anti-Histone), and to compare these results to a subset of ANAs measured by enzyme-linked immunosorbent assays (ELISA) and immunodiffusion (ID). Sera were obtained from 22 systemic lupus erythematosus (SLE) patients, twelve controls and five others (commercial source) with various autoimmune diseases. ANA results from the AtheNA MultiLyte ANA II Assay (AtheNA) were compared to ELISA results (controls) and patients (ID). The AtheNA interassay coefficients of variation (CVs, N = 39, performed in duplicate; replicated 3x) ranged from 6.2% to 16.7% (mean = 9.8%), while the intra-assay CVs ranged from 5.8% to 14.3% (mean = 10.8%). Compared to results for SLE cases and controls, the sensitivity of AtheNA ranged from 85.7% to 100% (mean = 97.1%), while diagnostic specificity ranged from 16.7% to 100% (mean = 71.6%). There was significant agreement (P values ranging from 0.0001 to 0.03) when analytes coanalyzed by AtheNA and ELISA/ID were evaluated using Cohen's kappa (kappa values ranging from 0.376 to 1.000). No false positive ANA results were observed for either the control or commercial source autoimmune disease sera. These results indicate that the AtheNA assay is a precise and accurate alternative for performing multiple ELISAs or IDs in the diagnosis of autoimmune diseases, especially when the number of sera to be tested is large, such as in clinical screening or epidemiologic studies. It also appears that the AtheNA assay identifies positive ANA specificities which are missed by ID techniques, suggesting that it may have greater analytical sensitivity for some ANAs.

Clinical features and prognosis of patients with idiopathic inflammatory myopathies and anti-Jo-1 antibodies

The idiopathic inflammatory myopathies are a heterogeneous group of diseases that can involve various systems. Antibodies directed against aminoacyl-tRNA synthetases, such as anti-Jo-1 antibodies, are strongly associated with a syndrome which consists of myositis, interstitial lung disease (ILD), arthritis and Raynaud's phenomenon. Forty-one patients with various forms of idiopathic inflammatory myopathies were assessed: 14 patients with anti-Jo-1 antibodies and 27 patients without anti-Jo-1 antibodies as a control group. We retrospectively analysed clinical symptoms, treatment and outcome in both groups. Patients with anti-Jo-1 antibodies more often had ILD (64.2 vs. 11.1%), arthritis (64.2 vs. 18.1%) and Raynaud's phenomenon (38 vs. 0%). Patients without the anti-Jo-1 antibody presented worse muscle strength and more frequently myalgia (37 vs. 21%), cutaneous rash (18.5 vs. 7%), heliotrope rash (29% vs. 7%) and periungueal changes (22 vs. 0%) than the anti-Jo-1-positive patients. Outcome was good in both groups. Improvement was achieved in the 14 (100%) Jo-1 positive patients, and in 25 (92.5%) controls. Two (7.5%) patients from control group achieved remission.

Evaluation of a standard immunofluorescence assay and a new flow cytometric method for the detection of autoreactive antibodies in dogs with tumours

The major purpose of the presented study was to develop and to evaluate a flow cytometry-based assay (IIFC) for the determination of autoreactive antibodies in sera from canine cancer patients. A blinded study demonstrated the poor reproducibility of the standard, slide-based and microscopically evaluated indirect immunofluorescence test (IIF), especially with sera displaying a cytoplasmic reactivity. In the IIFC, the intra assay coefficient of variance ranged between 5% and 11%, the inter assay variance between 8% and 25%. The IIFC resulted in significantly less positive results among canine cancer patients (16%) than the IIF (40%). The latter results were due to low titered sera indicating that the standard assay may lead to a high proportion of false positive results. The limitation of the IIFC is that no conclusions can be made about the sub cellular localization of the fluorescence. However, this cytometry-based assay makes a more objective and standardized detection of canine autoreactive antibodies possible.

[Auto-antibodies to anti-ENA SSA/RO (52 and 60 kDa): an auto-immunity laboratory's experience]

PURPOSE

Anti-SSA/Ro and anti-SSB/La autoantibodies are frequently encountered in SLE or SGS where anti-SSA subtypes 52 and 60 kDa seems to be differently found in connection with the disease type: anti-SSA/Ro 60 kDa more frequently found in SLE and anti-SSA/Ro 52 kDa in SGS. We try to find if it was interesting in identifying these specificities for all anti-ENA screening.

METHOD

The study included 162 patients' sera found anti-SSA 52 and/or anti-SSA 60 and/or anti-SSB positive among 1600 screening tests from the different hospital's services. We used two assays: first, dotblot (Innolia-Ana Update INGEN) as a screening test and second, an Elisa (ENA-LISA BMD) as confirmation. Thirty-eight control sera were found negative with dotblot.

RESULTS

Only one subtype of anti-SSA (52 or 60 kD) or anti-SSB was found for 55 sera (44 anti-SSA 52, 10 anti-SSA 60, 1 anti-SSB) and 107 sera were found positive for two or more (73 anti-SSA 52 + 60 and 34 anti-SSA 52 or 60 with another anti-ENA). While anti-SSA 60 kDa alone or not was always positive with the Elisa test, neither anti-SSA 52 alone was anti-SSA Elisa's positive. Diseases associations results show a greater linking of anti-SSA 60 kDa with SLE, a frequent linking of combined reactivity anti-SSA 52/60 in SLE and SGS and a greater spreading of anti-SSA 52 kDa alone among pathological groups, showing an autoimmune disease's linking in 68%. Among SGS, 29% had only anti-SSA 52 kDa.

CONCLUSION

We suggest screening specific tests for identifying anti-SSA/Ro 52 kDa reactivity which are missed by routine testing (tests using animal's antigens) and could represent an additional serum marker in Connective Tissue Diseases.

Utility of age, gender, ANA titer and pattern as predictors of anti-ENA and -dsDNA antibodies

Monovariate and multivariate analyses including logistic regression were performed to determine associations among predicting variables [age, gender, immunofluorescence pattern, and anti-nuclear antibody (ANA) titer] and anti-extractable nuclear antigen (ENA) and -dsDNA antibodies (Abs) in 1089 patients with positive fluorescent ANA (FANA) test results. Samples with high titer ANAs had an increased frequency of anti-ENA and -dsDNA Abs. The receiver operating (ROC) curves of the ANA titer for anti-ENA Abs had a larger under the curve area compared to the ROC curve for anti-dsDNA Abs, indicating that ANA titer is better for predicting anti-ENA Abs than anti-dsDNA Abs. There was no relation noticed between immunofluorescence patterns and anti-ENA and -dsDNA Abs except an increased frequency of anti-dsDNA Abs found in samples with a homogeneous pattern. Probability calculations on the basis of the ANA pattern and the titer showed that samples with low titer ANAs (1:160 or less) had low probabilities for anti-ENA Abs (0.002-0.009) regardless of immunofluorescence patterns. However, samples with a homogeneous pattern at any titers including low titers had high probabilities for anti-dsDNA Abs. A decreased frequency of anti-dsDNA Abs as measured by Crithidia assay was noticed in samples from patients aged 50 or older. In contrast, no association was noticed between age and anti-ENA Abs. There was no female preponderance found in the presence of anti-ENA and -dsDNA Abs. In conclusion, our study shows that the ANA titer but not the immunofluorescence pattern is useful in predicting anti-ENA Abs. In contrast, both the ANA titer and the immunofluorescence pattern help in predicting anti-dsDNA Abs. Samples with low titer ANAs (1:160 or less) may not need a further test for anti-ENA Abs unless an ANA-associated disease is highly suspected. However, a test for anti-dsDNA Abs should be considered in samples with a homogeneous pattern at any titer including low titers.

Diagnostic associations in a large and consecutively identified population positive for anti-SSA and/or anti-SSB: the range of associated diseases differs according to the detailed serotype

OBJECTIVE

To determine the diagnostic distribution in a consecutive anti-SSA and/or anti-SSB positive population.

METHODS

A total of 15 937 serum samples from 10 550 consecutive patients were analysed for antinuclear antibodies (ANAs) on HEp-2 cells. Serum samples positive for ANAs were analysed by immunodiffusion and line immunoassay with recombinant SSA-Ro52, natural SSA-Ro60, and recombinant SSB.

RESULTS

Among ANA positive patients in whom clinical information was available, 181 consecutive patients with anti-SSA and/or anti-SSB antibodies were identified, Disease associations were systemic lupus erythematosus (SLE) (45.3%), primary Sjögren's syndrome (pSS) (14.4%), scleroderma (8.8%), RA (7.7%), cutaneous lupus (7.7%), and dermatomyositis (2.2%). The ratio of diagnoses differed according to the anti-SSA/anti-SSB serotype. Scleroderma and dermatomyositis were enriched among mono-Ro52 reactive serum samples (34.2% and 10.5% respectively). Single reactivity towards Ro60 or anti-Ro60 with anti-Ro52 predisposed for SLE (80.0% and 52.2% respectively). Triple reactivity towards Ro52, Ro60, and SSB was primarily linked with SLE (55.8%) followed by pSS (20.9%). Anti-SSA on immunodiffusion increased the chance for SLE (62.8%), whereas isolated anti-SSB reactivity on immunodiffusion was less indicative for SLE (14.3%) and predisposed more for cutaneous lupus (23.8%) and pSS (33.3%).

CONCLUSION

The diagnostic range associated with anti-SSA or anti-SSB reactivity differs significantly according to the detailed serotype defined by line immunoassay and immunodiffusion.

Detection of Specific Antinuclear Reactivities in Patients with Negative Anti-nuclear Antibody Immunofluorescence Screening Tests

Background: For detection of anti-nuclear antibodies (ANAs) and antibodies to extractable nuclear antigens (ENAs), samples frequently are screened with indirect immunofluorescence (IIF); further determination of anti-ENA antibodies is performed only when the result is positive. However, because anti-ENA reactivities are found in samples with low fluorescence intensities, we determined anti-ENA antibodies in samples with negative IIF and thus calculated the sensitivity of IIF for specific ANAs.

Methods: We collected 494 samples consecutively referred by rheumatologists for routine ANA testing. IIF on HEp-2 and HEp-2000 (HEp-2 cells transfected with Ro60 cDNA) and line immunoassay (LIA) for the detection of specific ANAs were performed on all samples.

Results: Fluorescence intensities and patterns on HEp-2 were strongly correlated with those on HEp-2000 [Spearman ρ = 0.852 (P &lt;0.001) and 0.838 (P &lt;0.001), respectively]. Sixty-eight of 494 samples were positive on LIA, of which only 72% (confidence interval, 68–76%) were detected with HEp-2 and 75% (confidence interval, 70–78%) with HEp-2000. Of 291 samples negative on both substrates, 12 were positive on LIA. Connective tissue diseases were diagnosed in four of these patients and suspected in at least three others.

Conclusion: The HEp-2 and HEp-2000 substrates perform comparably for fluorescence intensities and patterns and for detecting specific ANAs, but some patients with negative IIF show reactivity on LIA. We recommend testing for fine reactivities, regardless of the IIF result, when the clinical suspicion for rheumatic connective tissue disease is high.