Antibodies to extractable nuclear antigens. Has technological drift affected clinical interpretation?

The axis of complement C1 and nucleolus in antinuclear autoimmunity

Antinuclear autoantibodies (ANA) are heterogeneous self-reactive antibodies that target the chromatin network, the speckled, the nucleoli, and other nuclear regions. The immunological aberration for ANA production remains partially understood, but ANA are known to be pathogenic, especially, in systemic lupus erythematosus (SLE). Most SLE patients exhibit a highly polygenic disease involving multiple organs, but in rare complement C1q, C1r, or C1s deficiencies, the disease can become largely monogenic. Increasing evidence point to intrinsic autoimmunogenicity of the nuclei. Necrotic cells release fragmented chromatins as nucleosomes and the alarmin HMGB1 is associated with the nucleosomes to activate TLRs and confer anti-chromatin autoimmunogenecity. In speckled regions, the major ANA targets Sm/RNP and SSA/Ro contain snRNAs that confer autoimmunogenecity to Sm/RNP and SSA/Ro antigens. Recently, three GAR/RGG-containing alarmins have been identified in the nucleolus that helps explain its high autoimmunogenicity. Interestingly, C1q binds to the nucleoli exposed by necrotic cells to cause protease C1r and C1s activation. C1s cleaves HMGB1 to inactive its alarmin activity. C1 proteases also degrade many nucleolar autoantigens including nucleolin, a major GAR/RGG-containing autoantigen and alarmin. It appears that the different nuclear regions are intrinsically autoimmunogenic by containing autoantigens and alarmins. However, the extracellular complement C1 complex function to dampen nuclear autoimmunogenecity by degrading these nuclear proteins.

What does it mean if a patient is positive for anti-Jo-1 in routine hospital practice? A retrospective nested case-control study

Background:  It is widely believed that patients bearing auto-antibodies to histidyl tRNA synthetase (anti-Jo-1) very likely have a connective tissue disease including myositis and interstitial lung disease.  The value of positive tests in low disease prevalence settings such as those tested in routine care is unknown.  We sought to determine the value of anti-Jo-1 auto-antibodies in routine practice. Methods: Our study was a nested case control study within a retrospective cohort of all patients tested for anti-ENA our hospital, from any hospital department, between January 2013 and December 2014.  Data was extracted from electronic records of anti-Jo-1 positive patients and randomly selected ENA negative patients (ratio of 1:2), allowing for a minimum follow up of at least 12 months after first testing. Results: 4009 samples (3581 patients) were tested.  Anti-ENA was positive in 616 (17.2%) patients, 40 (1.1%) were anti-Jo-1 positive. Repeat ENA testing was done for 350/3581 (9.8%) patients (428 of 4009 (10.7%) samples) and in 7/40 (17.5%) of anti-Jo-1 positive patients. The median interval between the first and second request was 124 days (inter-quartile range 233 days).  The frequencies of interstitial lung disease (ILD), myositis and Raynaud's were comparable for anti-Jo-1 positive patients (n=40) and 80 randomly selected ENA negative controls.  Positive tests led to additional diagnostic testing in the absence of clinical disease.  Sensitivity of Jo-1 for ILD was 50% (CI 19-81%), specificity 68% (CI 59-77%), positive predictive value 12.5% (CI 4 to 27%) and negative predictive value 93.8% (CI 86-98%). Of 10 (25%) patients with high anti-Jo1 levels, 3 had ILD, one myositis and two a malignancy (disseminated melanoma and CML).  Conclusion: Anti-Jo-1 is uncommon in a heterogenous hospital population and is only weakly predictive for ILD.  Repeated test requests were common and potentially unnecessary indicating that controls over repeat requests could yield significant cost savings.

Next-Generation Autoantibody Testing by Combination of Screening and Confirmation-the CytoBead® Technology

Occurrence of autoantibodies (autoAbs) is a hallmark of autoimmune diseases, and the analysis thereof is an essential part in the diagnosis of organ-specific autoimmune and systemic autoimmune rheumatic diseases (SARD), especially connective tissue diseases (CTDs). Due to the appearance of autoAb profiles in SARD patients and the complexity of the corresponding serological diagnosis, different diagnostic strategies have been suggested for appropriate autoAb testing. Thus, evolving assay techniques and the continuous discovery of novel autoantigens have greatly influenced the development of these strategies. Antinuclear antibody (ANA) analysis by indirect immunofluorescence (IIF) on tissue and later cellular substrates was one of the first tests introduced into clinical routine and is still an indispensable tool for CTD serology. Thus, screening for ANA by IIF is recommended to be followed by confirmatory testing of positive findings employing different assay techniques. Given the continuous growth in the demand for autoAb testing, IIF has been challenged as the standard method for ANA and other autoAb analyses due to lacking automation, standardization, modern data management, and human bias in IIF pattern interpretation. To address these limitations of autoAb testing, the CytoBead® technique has been introduced recently which enables automated interpretation of cell-based IIF and quantitative autoAb multiplexing by addressable microbead immunoassays in one reaction environment. Thus, autoAb screening and confirmatory testing can be combined for the first time. The present review discusses the history of autoAb assay techniques in this context and gives an overview and outlook of the recent progress in emerging technologies.

Uncertainty of measurement: an immunology laboratory perspective

'Measurement uncertainty of measured quantity values' (ISO15189) requires that the laboratory shall determine the measurement uncertainty for procedures used to report measured quantity values on patients' samples. Where we have numeric data measurement uncertainty can be expressed as the standard deviation or as the co-efficient of variation. However, in immunology many of the assays are reported either as semi-quantitative (i.e. an antibody titre) or qualitative (positive or negative) results. In the latter context, measuring uncertainty is considerably more difficult. There are, however, strategies which can allow us to minimise uncertainty. A number of parameters can contribute to making measurements uncertain. These include bias, precision, standard uncertainty (expressed as standard deviation or coefficient of variation), sensitivity, specificity, repeatability, reproducibility and verification. Closely linked to these are traceability and standardisation. In this article we explore the challenges presented to immunology with regard to measurement uncertainty. Many of these challenges apply equally to other disciplines working with qualitative or semi-quantitative data.

Performance of a multiplex assay compared to enzyme and precipitation methods for anti-ENA testing in systemic lupus and systemic sclerosis

INTRODUCTION

Testing for autoantibodies to extractable nuclear antigens (ENA) is essential in the investigation of connective tissue disease. Counterimmunoelectrophoresis is an early described testing methodology for antibodies to ENAs, but is labour-intensive, only moderately sensitive, and reliant on high-quality reference sera. Enzyme-linked immunosorbent assay (ELISA) is automatable for relatively high sample throughput, but has issues with false positives. The addressable laser bead immunoassay (ALBIA) is a multiplex technology which can assess several antibody specificities simultaneously on a small serum sample. We report performance of an ALBIA system compared with CIE and ELISA.

METHODS

Samples from 100 systemic sclerosis patients attending Royal Free Hospital in 2007 and 99 SLE patients attending St Thomas's Hospital in 2007-2008 were studied. All samples were tested for antibodies to RNP, Sm, Ro, La, Scl-70, Jo-1 by in-house CIE, FIDIS™ ALBIA (BMD, France), and ELISAs (Phadia, Germany). Cohen's kappa coefficient was used to examine agreement of the different assay methods for the same antibody. McNemar's test was used to detect differences between methodologies.

RESULTS

One sample was positive for anti-Jo-1 by CIE, & confirmed by ALBIA & ELISA. All 198 remaining samples were anti-Jo-1 negative by all 3 methods. With respect to RNP, Ro, La, Scl-70 antibodies, there was good agreement in assay performance between CIE, ALBIA, and ELISA. For Sm, agreement was less good between CIE and ELISA (kappa 0.491), and ALBIA and ELISA (kappa 0.403). Using McNemar's test performance was no different between the 3 assays, with the following exceptions: between CIE and ELISA for Ro-60 (p<0.01) and RNP (p<0.05), and between ALBIA and ELISA for RNP (p<0.01).

CONCLUSIONS

The FIDIS™ ALBIA produced similar level of performance as CIE, but with advantages of automation, and less dependence on highly skilled operators. ALBIA represents a potential advancement applicable to routine Immunology diagnostics.

Antinuclear antibodies and their detection methods in diagnosis of connective tissue diseases: a journey revisited

It has been more than 50 years since antinuclear antibodies were first discovered and found to be associated with connective tissue diseases. Since then different methods have been described and used for their detection or confirmation. For many decades immunofluorescent antinuclear antibody test has been the "gold standard" in the diagnosis of these disorders. However to increase the sensitivity and specificity of antinuclear antibody detection further approaches were explored. Today a battery of newer techniques are available some of which are now considered better and are competing with the older methods. This article provides an overview on advancement in antinuclear antibody detection methods, their future prospects, advantages, disadvantages and guidelines for use of these tests.

Clinical features of 39 patients with antibodies to extractable nuclear antigens despite negative antinuclear antibodies: evidence for autoimmunity including neurologic and connective tissue diseases

Systemic lupus erythematosus (SLE) rarely presents with a negative antinuclear antibody (ANA). Although antibodies to extractable nuclear antigens (ENA) are sometimes ordered despite a negative ANA, it is unclear if this contributes to the diagnosis of SLE or other forms of connective tissue disease (CTD). We reviewed 39 patients with anti-ENA antibodies despite a negative ANA during a 1-year period to determine the presence of SLE or other CTD. Several patients had clinical features suggestive of CTD, including 1 with possible SLE. A number of patients had neurologic disorders, especially peripheral neuropathy. In this study, the finding of anti-ENA despite negative ANA was associated with neurologic disorders and CTD. This may represent test bias or false-positive anti-ENA assays or false-negative ANA assays, or may imply immune-related mechanisms not previously described.

[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.

Update on the immunology, diagnosis and management of systemic lupus erythematosus

Lupus occurs with a prevalence of 2-9 in 10,000 people, targeting female and indigenous populations in particular. Lupus and related systemic autoimmune syndromes (scleroderma, Sjögren's syndrome, rheumatoid arthritis and polymyositis) result from a similar set of genetically and environmentally modulated immune disturbances, and the diagnostic and management approach to these conditions is broadly comparable. Evanescent, vague symptoms, restrictive diagnostic criteria and low diagnostic suspicion might have resulted in the under-diagnosis of these problems in the past, imposing considerable burdens on sufferers and the community. Serological screening should be employed cautiously and wisely, given the rapidly occurring changes in methodology, which have lowered their specificity. Close liaison with the immunology laboratories performing these tests is therefore advisable. Clinicians should emphasize the improving prognosis of lupus and related conditions as a result of earlier disease detection, improved educational support systems and refined medical therapies.

Practical evaluation of methods for detection and specificity of autoantibodies to extractable nuclear antigens

Detection and specificity of autoantibodies against extractable nuclear antigens (ENA) play a critical role in the diagnosis and management of autoimmune disease. Historically, the detection of these antibodies has employed double immunodiffusion (DID). Autoantibody specificity was correlated with diagnoses by this technique. Enzyme immunoassays have been developed by multiple manufacturers to detect and identify the specificity ENA autoantibodies. To address the relationship of ENA detection by DID and enzyme immunoassay, the performances of five immunoassays were compared. These included two DID and three enzyme-linked immunoassays (ELISA) (both screening and individual antigen profile kits). The sample set included 83 ENA-positive, antinuclear-antibody (ANA)-positive specimens, 77 ENA-negative, ANA-positive specimens, and 20 ENA- and ANA-negative specimens. Sensitivity and specificity were calculated by two methods: first, by using the in-house DID result as the reference standard, and second, by using latent class analysis, which evaluates each kit result independently. Overall, the results showed that the ELISA methods were more sensitive for detection of ENA autoantibodies than DID techniques, but presence and/or specific type of ENA autoantibody did not always correlate with the patient's clinical presentation. Regardless of the testing strategy an individual laboratory uses, clear communication with the clinical staff regarding the significance of a positive result is imperative. The laboratory and the clinician must both be aware of the sensitivity and specificity of each testing method in use in the clinical laboratory.

Is immunoglobulin A anti-tissue transglutaminase antibody a reliable serological marker of coeliac disease?

BACKGROUND

Anti-tissue transglutaminase (tTG) antibody is being used increasingly as a diagnostic tool in the serological investigation of coeliac disease. However, positive predictive values of immunoglobulin A (IgA) anti-tTG for coeliac disease in prospective studies have been disappointing and false-positive results are reported.

OBJECTIVE

To assess the clinical utility of cascade testing for anti-tTG and anti-endomysium antibody (AEA).

PATIENTS

Two unselected retrospective cohorts from routine diagnostic investigation for possible gluten sensitive enteropathy: group 1 comprised 57 cases seropositive for anti-tTG and group 2 comprised 52 cases seronegative for anti-tTG. In both groups, all cases had also undergone small-intestinal biopsy.

METHODS

Patients were assessed for the presence of IgA anti-tTG by enzyme-linked immunosorbent assay and for IgA AEA by immunofluorescence.

RESULTS

The positive predictive value of IgA anti-tTG for biopsy-confirmed coeliac disease was 54%. The positive predictive value of dual positivity for anti-tTG and AEA was 97%. The negative predictive value of IgA anti-tTG was 100%.

CONCLUSIONS

The data presented here support the use of IgA anti-tTG as an initial screen for coeliac disease. Coeliac disease is unlikely when IgA anti-tTG is absent. However, many false-positive results are seen, and clinical utility and diagnostic efficiency are improved markedly if positive results are confirmed with the more accurate, but labour-intensive, AEA assay.