A critical evaluation of enzyme immunoassays for detection of antinuclear autoantibodies of defined specificities. I. Precision, sensitivity, and specificity

False positive anti-Topoisomerase I (Scl-70) antibody results in clinical practice: A case series from a scleroderma referral center

PURPOSE

To determine if some patients who tested positive for anti-Scl-70 antibody in clinical practice, but did not have classifiable systemic sclerosis, were negative for anti-Scl-70 antibody by the more specific immunodiffusion method of testing.

METHODS

Patients evaluated by a rheumatologist at a Scleroderma referral center who had tested positive for anti-Scl-70 antibody prior to referral, but did not have classifiable SSc based on clinical criteria, were invited to undergo testing for anti-Scl-70 antibody by immunodiffusion. Patient demographics and clinical features were recorded at the time of their evaluation, and diagnostic testing results were reviewed using the medical records.

RESULTS

52 patients were enrolled over an 8-year period, with 48 (92.3%) testing negative and 4 (7.7%) testing positive for anti-Scl-70 antibody by immunodiffusion. Of the 48 patients who tested negative, 18 (37.5%) tested negative for ANA by indirect immunofluorescence, 33 (68.8%) did not have Raynaud's phenomenon, and 43 (89.6%) had ≤1 clinical criteria items based on the 2013 ACR/EULAR SSc classification criteria. Nevertheless, 21 (43.8%) patients who were negative for anti-Scl-70 antibody by immunodiffusion had undergone a chest CT and 14 (29.2%) had undergone an echocardiogram. A total of 23 patients had at least one follow up clinic visit. 3 out of 4 patients who were positive for anti-Scl-70 antibody by immunodiffusion, but none of the 19 patients who tested negative by immunodiffusion, developed sufficient criteria during follow up to be classified as SSc.

CONCLUSION

Assays for anti-Scl-70 antibody in commercial laboratories that are commonly utilized in clinical practice can produce false positive results. These results can lead to angst for patients, as well as unnecessary referrals and diagnostic evaluations.

Comparison of the effect of reporting cytoplasmic patterns as anti-nuclear antibody positive and anti-nuclear antibody negative on reflex test ordering

Objective Anti-nuclear antibody (ANA) patterns are classified as nuclear, cytoplasmic or mitotic. The International Consensus on ANA patterns (ICAP) suggests three parameters for ANA reporting – assay type, results and advice for reflex testing – but has not yet reached a consensus on the reporting of cytoplasmic/mitotic patterns as ANA-negative or positive. We investigated the effect of ICAP’s two proposals for reporting cytoplasmic patterns as ANA-positive and negative with a view to the recommendation for reflex testing in a country that has no national reimbursement policies for automatic reflex testing.

Methods This non-interventional descriptive study included 1241 patients with positive cytoplasmic ANA patterns. 442 patients were reported as ANA-negative and 799 as ANA-positive. Patients were followed up for a two-year period to determine testing recommendations based upon nuclear and cytoplasmic patterns. For statistical analysis, the t-test was used, with a significance threshold of p-value<0.05.

Results Appropriate reflex orders were seen more commonly with cytoplasmic patterns reported as ANA-positive (27.30%) than with those reported as ANA-negative (5.51%, p-value<0.05). However, ANA-positive reports led to higher ordering of nuclear pattern reflex tests (12.97%) compared with ANA-negative reports (1.10%, p-value<0.05). A large group of patients (59.73% ANA-positive, 93.39% ANA-negative) did not receive reflex testing.

Conclusion Reporting cytoplasmic patterns as ANA-positive was considered more significant, but reading the result report without considering the pattern and recommendation notes could lead to inappropriate reflex testing. Besides reaching a consensus for reporting cytoplasmic patterns as ANA-negative or positive, it is important to consider solutions to reimbursement policies for automatic reflex testing to decrease the impediments in reporting cytoplasmic ANA patterns.

Autoimmune markers in screening for orbital inflammatory disease

PURPOSE

Immunogenic causes of inflammation may be difficult to differentiate in the work-up of orbital inflammatory disease. The study aims to investigate the utility of autoimmune markers in the screening for orbital inflammation. Markers studied included angiotensin-converting enzyme (ACE), antinuclear antibody (ANA), anti-neutrophilic cytoplasmic autoantibodies (ANCA), extractable nuclear antigen (ENA), anti-cyclic citrullinated peptide (Anti-CCP) and anti-double stranded DNA antibody (Anti-dsDNA antibody).

METHODS

A retrospective single-centre study of consecutive patients with non-infective orbital inflammation screened for autoimmune markers at presentation. Serology was interpreted alongside clinical course and other investigations (e.g. radiographic features and histopathology). Tabulated data and Pearson's Chi-square allowed analysis of trends between serology, diagnosis and the decision to biopsy.

RESULTS

79 patients, between 1999 and 2021, were included (50 females, mean age was 50.4 ± 17.4 years). 28 (34.6%) patients had specific orbital inflammation and 53 (65.4%) patients had non-specific orbital inflammation (NSOI). Of the 12 patients with positive serology and a specific diagnosis, only 5 (41.7%) patients had concordant serological results. There was no association between serology results and the patient undergoing biopsy (P = 0.651). Serology was unable to exclude nor differentiate NSOI from other specific conditions and ANA had limited discriminatory value between specific conditions and NSOI.

CONCLUSION

Serological testing alone may not provide a clear direction for further investigation of orbital inflammation and a biopsy may occur independently of the serological results. The value of autoimmune markers may lie in subsequent follow-up as patients may develop suggestive symptoms after an indeterminate positive result or initially seronegative disease.

Case Report: Systemic Amyloidosis Involving the Heart and Skeletal Muscle

Background

Amyloidosis refers to an etiologically heterogeneous group of protein misfolding diseases characterized by extracellular deposition in organs and tissues of amyloid fibers, leading to severe organ dysfunction and death. Systemic amyloidosis often involves multiple organs. Heart and kidney are the most commonly affected organs, whereas skeletal muscle involvement is rare and often accompanied by other organs’ involvement.

Case Summary

We reported a 70-year-old man manifested with myopathy followed by heart failure who was suspected of transthyretin amyloidosis clinically, after the pathological results and the ^99mTc-pyrophosphate (^99mTc-PYP) scintigraphy, light-chain (AL) amyloidosis involving the heart and skeletal muscle was confirmed.

Conclusion

The patient’s unique presentation gives insight into a rare but debilitating disorder and the potential link between various types of amyloidosis. In addition, myopathy in amyloidosis should be recognized.

Current state of technologies and recognition of anti-SSA/Ro antibodies in China: A multi-center study

Background

Previous studies have demonstrated that Ro60 and Ro52 have different clinical implications, and anti‐Ro52 antibodies are an independent serum marker of systemic autoimmune diseases, including Sjögren's syndrome. Many different assays have been adopted to detect anti‐Sjögren's syndrome antigen A (SSA)/Ro antibodies, while to date no specific approach has been recommended as optimal for anti‐SSA/Ro antibody testing. Herein, we performed a multi‐center study to explore the current clinical utility of different strategies for anti‐SSA/Ro antibody testing in China.

Methods

Twenty‐one tertiary care centers were included in this questionnaire‐based study. The self‐administered questionnaire mainly includes testing methods for anti‐SSA/Ro antibodies, reporting system of results, and interpretation of results by clinicians.

Results

Six different methods were applied to detect anti‐SSA/Ro antibodies in the 21 centers. Line immunoassay (eight different commercial kits) was the most frequently adopted method (21/21, 100%), with different cutoff values and strategies for intensity stratification. There were two reporting systems: One was reported as “anti‐SSA antibodies” and “anti‐Ro52 antibodies” (12/21, 57%), while the other was “anti‐SSA/Ro60 antibodies” and “anti‐SSA/Ro52 antibodies” (9/21, 43%). Notably, six centers (29%) considered either positive anti‐Ro60 or anti‐Ro52 antibodies as positive anti‐SSA antibodies, all of which adopted the latter reporting system.

Conclusion

Significant variabilities existed among anti‐SSA/Ro assays. Nearly 30% of centers misinterpreted the definition of positive anti‐SSA antibodies, which may be attributed to the confusing reporting systems of line immunoassay. Therefore, we advocate standardization of the nomenclature of anti‐SSA/Ro antibodies, changing the “anti‐SSA/Ro52” label in favor of the “anti‐Ro52” antibodies for a clear designation.

The antinuclear antibody HEp-2 indirect immunofluorescence assay: a survey of laboratory performance, pattern recognition and interpretation

Background

To evaluate the interpretation and reporting of antinuclear antibodies (ANA) by indirect immunofluorescence assay (IFA) using HEp-2 substrates based on common practice and guidance by the International Consensus on ANA patterns (ICAP).

Method

Participants included two groups [16 clinical laboratories (CL) and 8 in vitro diagnostic manufacturers (IVD)] recruited via an email sent to the Association of Medical Laboratory Immunologists (AMLI) membership. Twelve (n = 12) pre-qualified specimens were distributed to participants for testing, interpretation and reporting HEp-2 IFA. Results obtained were analyzed for accuracy with the intended and consensus response for three main categorical patterns (nuclear, cytoplasmic and mitotic), common patterns and ICAP report nomenclatures. The distributions of antibody titers of specimens were also compared.

Results

Laboratories differed in the categorical patterns reported; 8 reporting all patterns, 3 reporting only nuclear patterns and 5 reporting nuclear patterns with various combinations of other patterns. For all participants, accuracy with the intended response for the categorical nuclear pattern was excellent at 99% [95% confidence interval (CI): 97–100%] compared to 78% [95% CI 67–88%] for the cytoplasmic, and 93% [95% CI 86%–100%] for mitotic patterns. The accuracy was 13% greater for the common nomenclature [87%, 95% CI 82–90%] compared to the ICAP nomenclature [74%, 95% CI 68–79%] for all participants. Participants reporting all three main categories demonstrated better performances compared to those reporting 2 or less categorical patterns. The average accuracies varied between participant groups, however, with the lowest and most variable performances for cytoplasmic pattern specimens. The reported titers for all specimens varied, with the least variability for nuclear patterns and most titer variability associated with cytoplasmic patterns.

Conclusions

Our study demonstrated significant accuracy for all participants in identifying the categorical nuclear staining as well as traditional pattern assignments for nuclear patterns. However, there was less consistency in reporting cytoplasmic and mitotic patterns, with implications for assigning competencies and training for clinical laboratory personnel.

Development of a Novel Multiplex Bead-based Assay for Measuring Autoantibodies on Flow Cytometric Platform

Background: Autoantibodies (AAbs) are important biomarkers for the diagnosis of Autoimmune Diseases (ADs). The detection of AAbs performed by current methods (indirect immunofluorescence test (IIFT)/Immunoblot (dot/line)/enzyme-linked immunosorbent assay ELISA) which have limitations in terms of performing multiple assays to arrive at laboratory diagnosis. We validated a novel multiplex bead-based assay (NMBA) that could quantify five common antibodies, simultaneously, on a flow-cytometry platform.Methods: A total of five recombinant antigens (SS-A Ro60, CENP B, RNP 70, Scl 70 and Histones) were covalently coupled onto beads and tested using known positive sera (positive for AAbs) and analyzed using flow cytometer.Results: The sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were obtained for each antigen, analyzed by both assays (NMBA and IIFT). It showed comparable or higher values for the NMBA. The Spearman's rank correlation coefficient (Rho) were ≥ 0.97, (P < .05), indicating that multiplexing of the five autoantigens did not alter the results obtained when antigens were tested individually. The mean intra-assay precision measured by coefficient of variation (CV) was7.56 ± 1.6% and the mean inter-assay CV was 10.03 ± 1.34%. The time taken from sample receipt to reporting of results was 90 minutes in NMBA as compared to 150 minutes of IIFTConclusion: The NMBA could quantitatively measure antibodies against five autoantigens, simultaneously in patient's sera. The assay is faster, objective, reproducible, requires low sample volume, and stable. Moreover, the flow cytometer in diagnostic laboratory settings for hematological and transplant immunology tests, can also be used for testing AAbs.

Higher Sensitivity Provided by the Combination of Two Lateral Flow Immunoassay Tests for the Detection of COVID-19 Immunoglobulins

SARS-Cov-2 was identified in Wuhan, China in December 2019. The World Health Organization (WHO) declared it a pandemic in March of 2020. COVID-19 has now been reported on every continent. In the United States, the total number of confirmed reported cases of COVID-19 has exceeded 1.8 million with the total death exceeding 100,000 people. The most common investigational diagnostics of this disease are RT-PCR and serology testing. The objective of this work was to validate two commercial kits for the detection of IgM and IgG using lateral flow immunoassay tests and to study the effect of the combination of both serology kits for better detection of immunoglobulins. A total of 195 patients presenting with respiratory symptoms suggestive of infection with SARS-Cov-2 were subject to serology and molecular testing. Two lateral flow immunochromatographic assay kits were used: the Healgen Scientific for SARS-CoV-2 IgM/IgG and the Raybiotech for SARS-CoV-2 IgM/IgG. Sensitivity and specificity of each kit alone and in combination were determined and compared. The limit of detection, inter and intra test variations, as well interfering substances and cross reactivity were also studied for both kits. The results show sensitivities for IgM detection varying between 58.9 and 66.2% for the kits alone and 87.7% of the combination of both kits. IgG detection was not significantly affected by this combination. Both kits manifested high specificities (99.2–100%). Both kits showed high clinical performance in terms of cross reactivity and interfering substances. Our results suggest using combinatory testing for the serology of COVID-19 after a full evaluation study, assessing all the parameters affecting their clinical performance before deciding on this combination.

Evaluation of a novel latex enhanced turbidimetric immunoassay for detecting autoantibody against extractable nuclear antigens

Detection of autoantibody against extractable nuclear antigens (ENAs) plays a critical role in the diagnosis and management of autoimmune diseases.In this study, we assessed the performance of LETIA in detecting anti-ENAs. Total 606 serum samples from the Second Hospital of Shanxi Medical University were collected. Anti-SSA, anti-SSB, anti-Sm, anti-U1-snRNP, and anti-Sm/RNP were parallelly detected by LETIA and line immunoblot (LIA). Besides, this study assessed LETIA for its repeatability in detecting anti-ENAs autoantibodies, and consistency with LIA. A receiver operating characteristic (ROC) curves was drawn to assess the accuracy of LETIA. The LETIA and LIA showed high coincidence rate in detecting anti-SSA, anti-SSB, anti-Sm, anti-U1-snRNP, and anti-Sm/RNP autoantibodies, with the results being 87.22%, 96.61%, 97.03%, 88.28%, and 92.06%, respectively. Almost perfect consistency (kappa > 0.8) were found in the detection of anti-SSB and anti-Sm by LETIA and LIA. While in the detection of anti-SSA, anti-U1-snRNP, and anti-Sm/RNP, moderate consistency (0.6 ⩽ kappa ⩽ 0.8) were shown. The AUCs of anti-SSA, anti-SSB, anti-Sm, anti-U1-snRNP, and anti-Sm/RNP detected by LETIA were 0.972 (95% confidence interval (CI): 0.941–1.000, p < 0.001), 0.986 (95% CI: 0.967–1.000, p < 0.001), 0.912 (95% CI: 0.763–1.000, p < 0.001), 0.829 (95% CI: 0.731–0.928, p < 0.001), and 0.828 (95% CI: 0.715–0.941, p < 0.001), respectively. LETIA and LIA showed considerable consistency in detecting anti-ENAs. Moreover, with the pronounced advantages of automatic and rapid detection, and high universality, LETIA can meet the requirements for quantitative detection of anti-ENAs.

Designing Paper-Based Immunoassays for Biomedical Applications

Paper-based sensors and assays have been highly attractive for numerous biological applications, including rapid diagnostics and assays for disease detection, food safety, and clinical care. In particular, the paper immunoassay has helped drive many applications in global health due to its low cost and simplicity of operation. This review is aimed at examining the fundamentals of the technology, as well as different implementations of paper-based assays and discuss novel strategies for improving their sensitivity, performance, or enabling new capabilities. These innovations can be categorized into using unique nanoparticle materials and structures for detection via different techniques, novel biological species for recognizing biomarkers, or innovative device design and/or architecture.

Anti-nuclear autoantibodies in systemic sclerosis : News and perspectives

Systemic sclerosis is a connective tissue disorder characterized by microvascular damage and excessive fibrosis of the skin and internal organs. One hallmark of the immunological abnormalities in systemic sclerosis is the presence of anti-nuclear antibodies, which are detected in more than 90% of patients with systemic sclerosis. Anti-centromere antibodies, anti-DNA topoisomerase I antibodies, and anti-RNA polymerase III antibodies are the predominant anti-nuclear antibodies found in systemic sclerosis patients. Other systemic sclerosis-related anti-nuclear antibodies include those targeted against U3 ribonucleoprotein, Th/To, U11/U12 ribonucleoprotein, and eukaryotic initiation factor 2B. Anti-U1 ribonucleoprotein, anti-Ku antibodies, anti-PM-Scl, and anti-RuvBL1/2 antibodies are associated with systemic sclerosis overlap syndrome. Anti-human upstream binding factor, anti-Ro52/TRIM21, anti-B23, and anti-centriole antibodies do not have specificity to systemic sclerosis, but are sometimes detected in sera from patients with systemic sclerosis. Identification of each systemic sclerosis-related antibody is useful to diagnose and predict organ involvement, since the particular type of systemic sclerosis-related antibodies is often predictive of clinical features, severity, and prognosis. The clinical phenotypes are largely influenced by ethnicity. Currently, an immunoprecipitation assay is necessary to detect most systemic sclerosis-related antibodies; therefore, the establishment of an easy, reliable, and simple screening system is warranted.

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.

The burden of the variability introduced by the HEp-2 assay kit and the CAD system in ANA indirect immunofluorescence test

According to the recent recommendations of the American College of Rheumatology, ANA Task Force, IIF technique should be considered the gold standard in antinuclear antibodies (ANAs) testing. To overcome the lack of standardization, biomedical industries have developed several computer-aided diagnosis (CAD) systems. Two hundred and sixty-one consecutive samples with suspected autoimmune diseases were tested for ANA by means of IIF on routinely HEp-2 assay kit (Euroimmun AG). Assignment of result was made if consensus for positive/negative was reached by at least 2 out of 3 expert physicians. ANA-IIF was also carried out using 3 CAD systems: Zenit G-Sight (n = 84), Helios (n = 85) and NOVA View (n = 92); human evaluation was repeated on the same substrate of each CAD system (Immco, Aesku and Inova HEp-2 cells, respectively). To anonymize the results, we randomly named these three systems as A, B and C. We ran a statistical analysis computing several measures of agreement between the ratings, and we also improved the evaluation by using the Wilcoxon's test for nonparametric data. Agreement between the human readings on routinely HEp-2 assay kit and human readings on CAD HEp-2 assay was substantial for A (k = 0.82) and B (k = 0.72), and almost perfect for C (k = 0.89). Such readings were statistically different only in case A. Comparing experts' readings with the readings of CAD systems, when the samples were prepared using CAD HEp-2 assay kits, we found almost perfect agreement for B and C (k = 0.86; k = 0.82) and substantial agreement for A (k = 0.73). Again, human and CAD readings were statistically different only in A. When we compared the readings of medical experts on routinely HEp-2 assay kit with the output of the CAD systems that worked using their own slides, we found substantial agreement for all the systems (A: k = 0.62; B: k = 0.65; C: k = 0.71). Such readings were not statistically different. The change of the assay kit and/or the introduction of a CAD system affect the laboratory reporting, with an evident impact on the autoimmune laboratory workflow. The CAD systems may represent one of the most important novel elements of harmonization in the autoimmunity field, reducing intra- and inter-laboratory variability in a new vision of the diagnostic autoimmune platform.

Recent Approaches To Optimize Laboratory Assessment of Antinuclear Antibodies

The presence of antinuclear antibodies (ANAs) is a hallmark of a number of systemic autoimmune rheumatic diseases, and testing is usually performed as part of the initial diagnostic workup when suspicion of an underlying autoimmune disorder is high. The indirect immunofluorescence antibody (IFA) technique is the preferred method for detecting ANAs, as it demonstrates binding to specific intracellular structures within the cells, resulting in a number of staining patterns that are usually categorized based on the cellular components recognized and the degree of binding, as reflected by the fluorescence intensity or titer. As a screening tool, the ANA patterns can guide confirmatory testing useful in elucidating a specific clinical diagnosis or prognosis. However, routine use of ANA IFA testing as a global screening test is hampered by its labor-intensiveness, subjectivity, and limited diagnostic specificity, among other factors. This review focuses on current efforts to standardize the nomenclature of ANA patterns and on alternative methods for ANA determination, as well as on recent advances in image-based computer algorithms to automate IFA testing in clinical laboratories.

Sjögren Syndrome: Why Do Clinical Trials Fail?

Sjögren syndrome (SS) comprises glandular and extraglandular manifestations. Double-blind prospective trials of traditional disease-modifying antirheumatic drugs and biologics have failed because they have not improved benign symptoms, the major cause of lowered quality of life. Rituximab has proven effective in SS patients with associated mixed cryoglobulinemia, parotid gland swelling, lymphocytic interstitial pneumonitis, thrombocytopenia, and other manifestations. There were few of these SS patients in the trials required for FDA approval. Most patients had benign symptoms and did not show benefit, leading to failure of the study. This article examines the reasons for these failures and proposes future directions.

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.

Current practice in laboratory diagnostics of autoimmune diseases in Croatia. Survey of the Working group for laboratory diagnostics of autoimmune diseases of the Croatian Society of Medical Biochemistry and Laboratory Medicine

INTRODUCTION

With the trend of increasing incidence of autoimmune diseases, laboratories are faced with exponential growth of the requests for tests relating the diagnosis of these diseases. Unfortunately, the lack of laboratory personnel experienced in this specific discipline of laboratory diagnostic, as well as an unawareness of a method limitation often results in confusion for clinicians. The aim was to gain insight into number and type of Croatian laboratories that perform humoral diagnostics with the final goal to improve and harmonize laboratory diagnostics of autoimmune diseases in Croatia.

MATERIALS AND METHODS

In order to get insight into current laboratory practice two questionnaires, consisting of 42 questions in total, were created. Surveys were conducted using SurveyMonkey application and were sent to 88 medical biochemistry laboratories in Croatia for the first survey. Out of 33 laboratories that declared to perform diagnostic from the scope, 19 were selected for the second survey based on the tests they pleaded to perform. The survey comprised questions regarding autoantibody hallmarks of systemic autoimmune diseases while regarding organ-specific autoimmune diseases was limited to diseases of liver, gastrointestinal and nervous system.

RESULTS

Response rate was high with 80 / 88 (91%) laboratories which answered the first questionnaire, and 19 / 19 (1.0) for the second questionnaire. Obtained results of surveys indicate high heterogeneity in the performance of autoantibody testing among laboratories in Croatia.

CONCLUSIONS

Results indicate the need of creating recommendations and algorithms in order to harmonize the approach to laboratory diagnostics of autoimmune diseases in Croatia.

Laboratory Investigations for Diagnosis of Autoimmune and Inflammatory Periocular Disease: Part II

PURPOSE

To review the important laboratory serological investigations routinely performed for the diagnosis of autoimmune and inflammatory diseases of the orbit and ocular adnexa.

METHODS

Review of the literature as well as personal clinical experience of the authors. Due to the extensive nature of the topic, the review has been split into 2 parts. Part I covers thyroid eye disease, IgG4-related disease, and myasthenia gravis. In part II of the review, sarcoidosis, vasculitis, Sjögren syndrome, and giant cell arteritis will be discussed.

RESULTS

Several relatively specific serologic tests are available for the diagnosis of a variety of inflammatory and serologic diseases of the orbit.

CONCLUSION

In cases of limited orbital or sino-orbital disease, serologic testing may be negative in a significant number of patients. Specifically, the clinician should be wary of ruling out limited orbital sarcoid or sinoorbital granulomatosis with polyangiitis based on serologic testing alone. Part I of this review has covered serologic testing for thyroid eye disease, IgG4-related disease, and myasthenia gravis. In part II, the authors discuss serologic testing for sarcoidosis, vasculitis, Sjögren syndrome (SS), and giant cell arteritis (GCA).

The Use of Poly-L-Lysine as a Capture Agent to Enhance the Detection of Antinuclear Antibodies by ELISA

Antibodies to nuclear antigens (antinuclear antibodies or ANAs) are the serological hallmark of systemic lupus erythematosus (SLE). These antibodies bind diverse nuclear antigens that include DNA, histones and non-histone proteins as well as complexes of proteins with DNA and RNA. Because of the frequency of ANA expression in SLE, testing is an important component of clinical evaluation as well as determination of eligibility for clinical trials or utilization of certain therapies. Immunofluorescence assays have been commonly used for this purpose although this approach can be limited by issues of throughput, variability and difficulty in determining positivity. ELISA and multiplex assays are also useful approaches although these assays may give an incomplete picture of antibodies present. To develop a sensitive and quantitative ANA assay, we have explored an ELISA platform in which plates are pre-coated with a positively charged nucleic acid binding polymer (NABP) to increase adherence of antigens containing DNA or RNA. As a source of antigens, we have used supernatants of Jurkat cells undergoing apoptosis in vitro. As results presented show, a poly-L-lysine (PLL) pre-coat significantly enhances detection of antibodies to DNA as well as antigens such as histones, SSA, SSB and RNP. Comparison of the ELISA assay with the PLL pre-coat with a multiplex assay using the BioPlex^® 2200 system indicated good agreement in results for a panel of lupus sera. Together, these studies indicate that a pre-coat with a positively charged polymer can increase the sensitivity of an ANA ELISA using as antigens molecules released from dead and dying cells. This assay platform may facilitate ANA testing by providing an ensemble of antigens more similar in composition and structure with antigens present in vivo, with a NABP promoting adherence via charge-charge interactions.

Dr Eng M. Tan: a tribute to an enduring legacy in autoimmunity

At the age of ninety years, Dr Eng Meng Tan has had a remarkable impact on the accumulated knowledge of autoimmune diseases, including seminal findings in systemic lupus erythematosus (SLE) and a wide range of other autoimmune diseases. Dating to the first description of the Sm (Smith) autoantibody in SLE, his focus has been the use of autoantibodies as probes to identify and elucidate novel cellular molecules and then translating these discoveries into biomarkers and immunoassays for a wide range of these diseases and, later, cancer. He led efforts to standardize autoantibody nomenclature and testing protocols. Through his mentorship a great number of trainees and collaborators have had remarkably successful careers, and by that virtue he has garnered a remarkable continuing legacy.

Detection of Antibodies to dsDNA: An Overview of Laboratory Assays

This brief review is focused on different methodologies available for detection of anti-dsDNA antibodies with respect to the best adequacy between biological results of laboratory and clinical significance. A large array of assays has been developed for the measurement of anti-dsDNA. New assays continually introduced have reflected not only technical innovations to avoid difficulties of some assays, but even more with hope to correlate better with systemic lupus erythematosus (SLE), particularly with its clinical course and exacerbations. Finally, with the development of micro arrays technology new insights into the pathophysiology of autoimmune disease processes should be revealed.

Clinical performance evaluation of a novel, automated chemiluminescent immunoassay, QUANTA Flash CTD Screen Plus

The QUANTA Flash(®) CTD Screen Plus is a chemiluminescent immunoassay (CIA) for the detection of the major antinuclear antibodies (ANA) on the BIO-FLASH(®) platform. NOVA View(®) is an automated fluorescence microscope that acquires digital images of indirect immunofluorescent assay (IFA) slides. Our goal was to evaluate the clinical performance of the two automated systems and compare their performance to that of traditional IFA. Sera from patients with systemic autoimmune rheumatic diseases (SARD, n = 178), along with disease and healthy controls (n = 204), were tested with the CTD CIA and with NOVA Lite(®) HEp-2 ANA, using both the manual method of reading the IFA slides and the NOVA View instrument. The CTD CIA showed 78.1% sensitivity for SARD, coupled with 94.1% specificity. Manual IFA and NOVA View showed somewhat higher sensitivity (81.5 and 84.8% in SARD, respectively), but significantly lower specificity (79.4 and 64.7%, respectively). Both automated systems displayed somewhat different performance, due to the different principals of ANA detection: IFA with NOVA View digital image interpretation had higher sensitivity, while the CTD CIA showed higher specificity. With the added benefits of full automation, the new CTD CIA is an attractive alternative to traditional ANA screening.

The Choice of Laboratory Methodology Influences Autoantibody Test Results

During the last 25 years, clinical autoantibody determinations have changed dramatically. Old and slow techniques with high diagnostic specificity have been replaced with automated and faster techniques that most often have a higher diagnostic sensitivity at the expense of a lower diagnostic specificity. Newer techniques are mostly quantitative, allowing for follow-up of autoantibody levels. Whereas the older procedures utilized autoantigens in soluble and native states, most modern techniques rely on autoantigens attached to surfaces, with the risk of exposure of denatured epitopes. Comparisons between antibody measurement techniques can be obtained from the results of external quality assessment programs. As the main objective for external quality assessment is the monitoring of clinical laboratories, they cannot focus on the kind of low-level and often polyreactive sera, which are common in the real world and in which a single definite target response cannot be easily defined. Such common sera are very useful, however, for analysis of differences between autoantibody measurement techniques. The European Consensus Finding Study Group on Autoantibodies has been working with this approach for 28 years.

Autoantibody to MDM2: A Potential Serological Marker of Systemic Lupus Erythematosus

Introduction. Systemic lupus erythematosus (SLE) is one of the systemic autoimmune diseases characterized by the polyclonal autoantibody production. The human homologue of the mouse double minute 2 (MDM2) is well known as the negative regulator of p53. MDM2 has been reported to be overexpressed in SLE animal model and to promote SLE. Since abnormally expressed proteins can induce autoimmune response, anti-MDM2 autoantibody was examined in SLE patients. Methods. Anti-MDM2 antibody in sera from 43 SLE patients and 69 healthy persons was investigated by ELISA. Positive samples were further confirmed by western blotting. The immunological feathers of anti-MDM2 positive sera were analyzed by indirect immunofluorescence assay. Anti-p53 was also investigated in SLE patients by ELISA, and the correlation of anti-MDM2 and anti-p53 was analyzed. Results. The presence of anti-MDM2 in SLE patients was 23.30%, much higher than normal healthy persons (4.30%). These anti-MDM2 positive sera present a nuclear staining pattern. The presence of anti-p53 in SLE patients was 39.50%, and the titer of anti-MDM2 was positively correlated with anti-p53 in SLE patients. Conclusions. Anti-MDM2 autoantibody was detected at high prevalence in SLE patients. The detection of anti-MDM2 in SLE patients should be clinically useful.

Characterization of immunoglobulin by mass spectrometry with applications for the clinical laboratory

Studies monitoring immunoglobulin (Ig) antigen specificity have brought to light key Ig biomarkers for immunity, autoimmunity, cancer detection, and immune system function evaluation. A fundamentally new approach to the detection of Igs based on the primary structure of the Ig is beginning to emerge in the literature. This approach has only become feasible in light of advances in proteomics and rapid improvements in mass spectrometry (MS). Driven primarily by the development of Ig pharmaceuticals, Ig MS-based proteomic methods are revealing structural features which were previously unavailable with other characterization techniques. The task of adapting these techniques to clinical chemistry is in its infancy, but these methods have the potential to dramatically alter testing for Ig biomarkers. The purpose of this article is to review the advances that have been made in proteomic characterization of Igs by MS and the early attempts to apply these methods to clinical samples.

Current concepts and future directions for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies

The detection of autoantibodies that target intracellular antigens, commonly termed anti-nuclear antibodies (ANA), is a serological hallmark in the diagnosis of systemic autoimmune rheumatic diseases (SARD). Different methods are available for detection of ANA and all bearing their own advantages and limitations. Most laboratories use the indirect immunofluorescence (IIF) assay based on HEp-2 cell substrates. Due to the subjectivity of this diagnostic platform, automated digital reading systems have been developed during the last decade. In addition, solid phase immunoassays using well characterized antigens have gained widespread adoption in high throughput laboratories due to their ease of use and open automation. Despite all the advances in the field of ANA detection and its contribution to the diagnosis of SARD, significant challenges persist. This review provides a comprehensive overview of the current status on ANA testing including automated IIF reading systems and solid phase assays and suggests an approach to interpretation of results and discusses meeting the problems of assay standardization and other persistent challenges.

Clinical phenotype associations with various types of anti-dsDNA antibodies in patients with recent onset of rheumatic symptoms. Results from a multicentre observational study

Despite anti-dsDNA antibodies constitute a wide range of specificities, they are considered as the hallmark for systemic lupus erythematosus (SLE).

Interpretation of ANA indirect immunofluorescence test outside the darkroom using NOVA view compared to manual microscopy

Objective. To evaluate NOVA View with focus on reading archived images versus microscope based manual interpretation of ANA HEp-2 slides by an experienced, certified medical technologist. Methods. 369 well defined sera from: 44 rheumatoid arthritis, 50 systemic lupus erythematosus, 35 scleroderma, 19 Sjögren's syndrome, and 10 polymyositis patients as well as 99 healthy controls were examined. In addition, 12 defined sera from the Centers for Disease Control and 100 random patient sera sent to ARUP Laboratories for ANA HEp-2 IIF testing were included. Samples were read using the archived images on NOVA View and compared to results obtained from manual reading. Results. At a 1 : 40/1 : 80 dilution the resulting comparison demonstrated 94.8%/92.9% positive, 97.4%/97.4% negative, and 96.5%/96.2% total agreements between manual IIF and NOVA View archived images. Agreement of identifiable patterns between methods was 97%, with PCNA and mixed patterns undetermined. Conclusion. Excellent agreements were obtained between reading archived images on NOVA View and manually on a fluorescent microscope. In addition, workflow benefits were observed which need to be analyzed in future studies.

A comparison of anti-nuclear antibody quantification using automated enzyme immunoassays and immunofluorescence assays

Anti-nuclear antibodies (ANA) have traditionally been evaluated using indirect fluorescence assays (IFA) with HEp-2 cells. Quantitative immunoassays (EIA) have replaced the use of HEp-2 cells in some laboratories. Here, we evaluated ANA in 400 consecutive and unselected routinely referred patients using IFA and automated EIA techniques. The IFA results generated by two independent laboratories were compared with the EIA results from antibodies against double-stranded DNA (dsDNA), from ANA screening, and from tests of the seven included subantigens. The final IFA and EIA results for 386 unique patients were compared. The majority of the results were the same between the two methods (n = 325, 84%); however, 8% (n = 30) yielded equivocal results (equivocal-negative and equivocal-positive) and 8% (n = 31) yielded divergent results (positive-negative). The results showed fairly good agreement, with Cohen's kappa value of 0.30 (95% confidence interval (CI) = 0.14–0.46), which decreased to 0.23 (95% CI = 0.06–0.40) when the results for dsDNA were omitted. The EIA method was less reliable for assessing nuclear and speckled reactivity patterns, whereas the IFA method presented difficulties detecting dsDNA and Ro activity. The automated EIA method was performed in a similar way to the conventional IFA method using HEp-2 cells; thus, automated EIA may be used as a screening test.

Diagnostic and clinical significance of anti-centromere antibodies in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease of the liver characterised by biochemical evidence of cholestasis, elevated alkaline phosphatase levels and the presence of the highly disease specific anti-mitochondrial autoantibodies. Extra-hepatic autoimmune manifestations are common, including rheumatic disorders, such as systemic sclerosis (SSc). Notably, PBC is the most frequent autoimmune liver disease in SSc patients. Based on skin lesion extension, two major SSc disease subgroups are recognised: limited cutaneous SSc (lSSc) and diffuse cutaneous SSc. Anti-centromere antibody (ACA) positivity is highly characteristic of SSc, with up to 90% prevalence in lSSc patients. ACA has also been found in up to 30% of PBC patients and 80% of patients with a PBC/SSc overlap syndrome. The diagnostic and clinical significance of ACA positivity in patients with PBC without SSc has recently been under investigation, with several studies highlighting links to severe bile duct injury and portal hypertension. This review discusses the diagnostic and clinical relevance of ACA in patients with PBC, with or without SSc.

Dissecting complex epigenetic alterations in human lupus

Systemic lupus erythematosus is a chronic relapsing autoimmune disease that primarily afflicts women, and both a genetic predisposition and appropriate environmental exposures are required for lupus to develop and flare. The genetic requirement is evidenced by an increased concordance in identical twins and by the validation of at least 35 single-nucleotide polymorphisms predisposing patients to lupus. Genes alone, though, are not enough. The concordance of lupus in identical twins is often incomplete, and when concordant, the age of onset is usually different. Lupus is also not present at birth, but once the disease develops, it typically follows a chronic relapsing course. Thus, genes alone are insufficient to cause human lupus, and additional factors encountered in the environment and over time are required to initiate the disease and subsequent flares. The nature of the environmental contribution, though, and the mechanisms by which environmental agents modify the immune response to cause lupus onset and flares in genetically predisposed people have been controversial. Reports that the lupus-inducing drugs procainamide and hydralazine are epigenetic modifiers, that epigenetically modified T cells are sufficient to cause lupus-like autoimmunity in animal models, and that patients with active lupus have epigenetic changes similar to those caused by procainamide and hydralazine have prompted a growing interest in how epigenetic alterations contribute to this disease. Understanding how epigenetic mechanisms modify T cells to contribute to lupus requires an understanding of how epigenetic mechanisms regulate gene expression. The roles of DNA methylation, histone modifications, and microRNAs in lupus pathogenesis will be reviewed here.

The predictive value of anti-SS-A antibodies titration in pregnant women with fetal congenital heart block

OBJECTIVE

Fetal congenital complete heart block (CHB) is irreversible and is associated with significant mortality and morbidity. Anti-SS-A antibodies in the maternal sera are involved in its pathogenesis; however, the predictive value of the antibody titer and its role in prediction of this complication are controversial. The aim of this study was to determine the predictive value of maternal anti-SS-A antibodies on the development of fetal CHB.

METHODS

A retrospective chart review was performed for 189 cases of positive anti-SS-A antibodies determined by the double immunodiffusion (DID) method, and included 17 patients that developed fetal CHB. The relationship between the appearance of CHB and the anti-SS-A antibodies titer was examined.

RESULTS

An anti-SS-A antibodies titer of 1:32 or higher was identified by analyzing the receiver-operating characteristics (area under curve 0.72) curve. An anti-SS-A antibodies titer of 32 or more times greater than the upper limit by DID was a risk factor for fetal CHB (odds ratio 27.77, 95% confidence interval (CI) 1.91-21.02, P < 0.05) in the multivariate analysis. Among 107 cases of anti-SS-A antibodies titers of 1:32 or higher, 65 patients (60.7%) were treated with oral steroids. Of these, four patients had CHB (6.2%). This rate of CHB was significantly lower (P < 0.01) than the rate in patients not treated with steroids.

CONCLUSION

An anti-SS-A antibodies titer of 1:32 or higher in the maternal sera by DID was an independent risk factor for fetal CHB. In these patients, either antenatally administered prednisolone or betamethasone, was associated with a lower risk of fetal CHB.

Screening for IgG antinuclear autoantibodies by HEp-2 indirect fluorescent antibody assays and the need for standardization

We evaluated 5 commercially available HEp-2 antinuclear antibody (ANA) indirect fluorescent antibody (IFA) assays using patient serum samples from 45 patients with rheumatoid arthritis, 50 with systemic lupus erythematosus (SLE), 35 with scleroderma, 20 with Sjögren syndrome, 10 with polymyositis, and 100 healthy control subjects. In addition, 12 defined serum samples from the Centers for Disease Control and Prevention and 100 patient serum samples sent to ARUP Laboratories (Salt Lake City, UT) for ANA IFA testing were also examined (n = 372). Standardization among the HEp-2 IFA assays occurred when they exhibited the same titer ± 1 doubling dilution. Agreement of the 5 assays was 78%. Within the specific groups of serum samples, agreement ranged from 44% in scleroderma serum samples to 93% in healthy control subjects, with 72% agreement in the SLE group. Variations in slide and substrate quality were also noted (ie, clarity, consistency of fluorescence, cell size, number and quality of mitotic cells). Along with subjectivity of interpretation, HEp-2 IFA assays are also vulnerable to standardization issues similar to other methods for ANA screening.

Missing links in high quality diagnostics of inflammatory systemic rheumatic diseases: It is all about the patient!

The aim of this review is to focus attention on high quality diagnostics of systemic inflammatory rheumatic diseases. Though many steps in the diagnostic process from the first visit in a doctor’s office till a final diagnosis have been established a lot of things still must be done to improve quality assurance and secure fast and safe transmission of data from one step to the next. Some procedures inherent in early high quality diagnostics need to be worked out. A number of elements can be improved, some stumble stones can be removed, and a tighter collaboration between actors at different levels in the line of action in clinical and laboratory medicine can be organized. Several proposals have been made by international working groups such as the IUIS International Autoantibody Standardization Committee, and the EASI steering group in collaboration with their national EASI teams. Practical exercises carried out for more than three decades by the European Consensus Finding Study Group have proven to very useful. The review points at several principles worked out by these international expert groups can be useful in actual daily practice also in rheumatology. The hope is that the presentation will give rise to a continued discussion on how to link different parts of the diagnostic process together and strengthen collaboration between all teams involved in the diagnostic chain. The ultimate measure of success will be better clinical outcomes for patients and increased satisfaction in their families.

Anti-CENPI autoantibodies in scleroderma patients with features of autoimmune liver diseases

BACKGROUND

Anticentromere autoantibodies have been reported to be associated with scleroderma and serve as a marker in different rheumatic diseases in humans. Major centromere autoantigens described so far include constitutive kinetochore proteins such as CENPA, CENPB, CENPC and CENPH and facultative proteins such as CENPE, CENPF and INCENP. We examined the inner kinetochore component CENPI as a new putative centromere autoantigen in scleroderma patients.

METHODS

To test for the presence of CENPI centromere autoantibodies, 72 sera from patients with systemic lupus erythematosus and systemic sclerosis were assayed by immunofluorescence and further tested by immunoblots with an Nt-CENPI recombinant protein.

RESULTS

8 out of 31 (25.8%) patients diagnosed of scleroderma or Undifferentiated Connective Tissue Disease (UCTD) produced anti-CENPI autoantibodies. Epitopes were demonstrated to be located mainly but not exclusively in the N-terminal domain of the human CENPI protein. Five of the 8 (62.5%) CENPI positive sera also had other autoantibodies related to primary biliary cirrhosis. Further, two patients (25%) with anti-CENPI autoantibodies had concurrent diagnosis of primary biliary cirrhosis.

CONCLUSIONS

This study demonstrates that CENPI, a centromere protein that localizes to the inner kinetochore structure, is a human autoantigen. The significance of anti-CENPI autoantibodies could be relevant in scleroderma patients as a marker for concurrent autoimmune liver disease.

Enzyme-linked immunosorbent assay screening then indirect immunofluorescence confirmation of antinuclear antibodies: a statistical analysis

The purpose of this study was to analyze antinuclear antibody (ANA) screening by enzyme-linked immunosorbent assay (ELISA) followed by indirect fluorescent antibody (IFA) testing to confirm and characterize the pattern and titer of the antibody. We evaluated 4 ANA ELISAs and 1 HEp-2 IFA substrate in 224 clinically defined serum samples consisting of 30 from systemic lupus erythematosus (SLE) cases, 94 from rheumatoid arthritis cases, and 100 from healthy donors plus 495 serum samples submitted for routine ANA testing and 12 reference serum samples distributed by the Centers for Disease Control and Prevention. IFA tests were read independently by 2 certified medical technologists. ELISA sensitivities ranged from 90% to 97% compared with 80% by IFA in the SLE serum samples. The ELISAs had specificities of 36% to 94%, whereas the IFA had 99% specificity. Overall, ELISAs for ANA assays demonstrated better sensitivity and good specificity, suggesting ELISA is a more cost-effective alternative to IFA testing for initial ANA screening. Samples positive by ANA ELISA should be tested on HEp-2 to determine the titer and pattern.

Myositis-specific autoantibodies: detection and clinical associations

In recent years, the detection and characterization of (novel) autoantibodies is becoming increasingly important for the early diagnosis of autoimmune diseases. The idiopathic inflammatory myopathies (IIM, also indicated with myositis) are a group of systemic autoimmune disorders that involve inflammation and weakness of skeletal muscles. One of the hallmarks is the infiltration of inflammatory cells in muscle tissues. A number of myositis-specific autoantibodies have been identified and these may be associated with distinct IIM subclasses and clinical symptoms. Here, we review all myositis-specific autoantibodies identified today as well as their target proteins, together with their clinical associations in IIM patients. Post-translational modifications that might be associated with the generation of autoantibodies and the development of the disease are discussed as well. In addition, we describe well established autoantibody detection techniques that are currently being used in diagnostic laboratories, as well as novel multiplexed methods. The latter techniques provide great opportunities for the simultaneous detection of distinct autoantibodies, but may also contribute to the identification of novel autoantibody profiles, which may have additional diagnostic and prognostic value. The ongoing characterization of novel autoantibody specificities emphasizes the complexity of processes involved in the development of such autoimmune diseases.

Anti‐nuclear autoantibodies: clinical utility for diagnosis, prognosis, monitoring, and planning of treatment strategy in systemic immunoinflammatory diseases

The determination of serum autoantibodies to nuclear and cytoplasmic cell components is relevant to the diagnosis of chronic immunoinflammatory disorders. Detection is based on screening methods that allow antibody binding to intact cell structures, followed by use of assays to demonstrate their antigen target specificity. The results can be used to help clinicians set diagnosis and estimate prognosis, plan further diagnostic work-up, monitoring strategy and sometimes therapeutic approach. To obtain such accuracy of use clinicians need to be involved in revealing the differential diagnostic potential of the autoimmune serology test programme by furnishing detailed clinical data on patients from whom serum samples have been obtained. Borders between positive and negative values should aim at attaining a high diagnostic specificity towards clinically important disease controls.

Anti-Jo-1 Antibodies

Anti-Jo-1 antibody is a myositis specific autoantibody most commonly found in patients with idiopathic inflammatory myopathies (IIM). This antibody is directed against the histidyl-tRNA synthetase which catalyses the binding of the histidine to its cognate tRNA during protein synthesis. It can be considered a specific marker of IIM, predominantly found in 20-30% of patients with PM and in the 60-70% of those with interstitial pulmonary fibrosis. These antibodies are also found in DM, although less frequently than in PM, and are rare in children with PM or DM and in other connective tissue diseases.ELISA, CIE and immunoblotting are highly specific and sensitive techniques for testing anti-Jo-1 antibodies. The detection of this antibody is particularly useful in diagnosis and classification of IIM. Moreover, anti-Jo-1 serum levels strongly correlate with disease activity representing a good marker for disease monitoring.