Comparison of Different Test Systems for Simultaneous Autoantibody Detection in Connective Tissue Diseases

Analytical and clinical performance of different platforms simultaneously detecting 15 antinuclear antibodies

Background

Antinuclear antibodies (ANAs) are invaluable biomarkers for the diagnosis of autoimmune diseases (AIDs). This study aims to compare the performances of line immunoassay (LIA), multiplex bead‐based flow fluorescent immunoassay (MBFFI), and magnetic bar code immunofluorescence assay (MBC‐IF) to detect ANA‐Profile‐15S.

Methods

In total, 184 samples from AID patients and 50 healthy controls (HCs) were collected. Fifteen ANAs (anti‐dsDNA, nucleosome, histone, Sm, PCNA, ribosomal‐P, SS‐A/Ro52, SS‐A/Ro60, SS‐B/La, centromere B [CENP‐B], Scl‐70, U1‐snRNP, AMA‐M2, Jo‐1, and Pm/Scl) were subjected to parallel detection by the LIA, MBFFI, and MBC‐IF. The consistency between assays was analyzed. The discrepant results were further examined by chemiluminescent immunoassay (CLIA).

Results

Anti‐SS‐A/Ro52 and SS‐A/Ro60 autoantibodies were the most common autoantibodies in ANA positive‐profiles, and were detected with equal efficiency by the LIA, MBFFI, and MBC‐IF (p = 0.101 and p = 0.732, respectively). The three assays showed excellent agreement (consistency range: 66.5%–97.5%), and total consistency was 85.8%. The MBFFI and MBC‐IF assays were in good agreement in terms of ANA‐Profile‐15S determination; the kappa coefficient ranged from 0.59 to 0.95, except for the PCNA and PM‐Scl. Of the 262 re‐assessed divergent results, 124 (47.33%) were positive on CLIA; the various autoantibodies exhibited variable patterns. More importantly, the ANA‐Profile‐15S results of the MBFFI and MBC‐IF accurately identified patients with AID; the area under the curves ranged from 0.642 to 0.919.

Conclusions

The novel MBFFI and MBC‐IF assay performed well in detecting ANA‐Profile‐15S. The application of MBFFI and MBC‐IF play important roles in laboratory diagnosis of AIDs.

Current technologies for anti-ENA antibody detection: State-of-the-art of diagnostic immunoassays

BACKGROUND

Autoantibodies against extractable nuclear antigens (ENA) play a pivotal role in the diagnosis and classification of systemic autoimmune rheumatic diseases (SARD). In recent years, newly developed methods have enabled the simultaneous and quantitative detection of multiple anti-ENA reactivities. However, data regarding the comparability of results obtained using different technologies across different platforms are scarce. In this study we compared eight different immunoassays, commonly used in current laboratory practice for detection of anti-ENA antibodies.

METHODS

Sixty patients suffering from different SARD, 10 inflammatory arthritis patients (disease controls) and 10 healthy blood donors were included in this comparative study. Sera were collected in 15 centers belonging to the Study Group on Autoimmune Diseases of the Italian Society of Clinical Pathology and Laboratory Medicine. We evaluated the analytical sensitivity, specificity and diagnostic accuracy of each method for antibodies to Sm, RNP, Ro60, Ro52, Scl70, CENP-B and Jo1. Cohen's kappa was used to analyze the agreement among methods.

RESULTS

Average agreement among methods was 0.82, ranging from substantial (k = 0.72) to almost perfect (k = 0.92). However, while the specificity was very good for all methods, some differences emerged regarding the analytical sensitivity.

CONCLUSIONS

Diagnostic performance of current technologies for anti-ENA antibody detection showed good comparability. However, as some differences exist among methods, laboratory scientists and clinicians must be aware of the diagnostic accuracy of the testing method in use.

Performance of Anti-Topoisomerase I Antibody Testing by Multiple-Bead, Enzyme-Linked Immunosorbent Assay and Immunodiffusion in a University Setting

BACKGROUND/OBJECTIVE

The criterion standard for anti-topoisomerase I antibody (anti-topo I antibody) testing in systemic sclerosis (SSc) uses immunodiffusion (ID) techniques, but enzyme-linked immunosorbent assay (ELISA) and multiple-bead technology are often used in current settings to save time and cost. Our aim was to assess the performance of the multiple-bead assay, ELISA, and ID testing methods.

METHODS

We conducted a retrospective study of patients at the University of Michigan whose extractable nuclear antigen 10 autoantibody panel tested positive for the anti-topo I antibody by multiple-bead technology during a 1-year period. All samples positive by multiple-bead assay were sent to the RDL Laboratories and reflexed for ELISA, and all anti-topo I antibodies positive by ELISA were further tested by ID. Clinical data were reviewed by a rheumatologist and assessed for presence of SSc. Data were analyzed via frequency tables.

RESULTS

Approximately 9500 extractable nuclear antigen 10 panels were ordered by physicians at the University of Michigan. Of these, 129 patients were positive for the anti-topo I antibody by multiple-bead assay, 51 were positive by multiple-bead assay and ELISA, and 21 were positive by multiple-bead assay, ELISA, and ID. We found that 26.4% of patients positive by multiple-bead assay, 47.1% positive by multiple-bead assay and ELISA, and 95.2% positive by multiple-bead assay, ELISA, and ID had SSc.

CONCLUSIONS

Multiple-bead assays have a high rate of false-positive results for the anti-topo I antibody in patients without clinical evidence of SSc. A stepwise approach of confirmation of positive multiple-bead assay results using both ELISA and ID improves the predictive value of antibody testing for the diagnosis of SSc.

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.

Automated Processing and Evaluation of Anti-Nuclear Antibody Indirect Immunofluorescence Testing

Indirect immunofluorescence (IIF) is considered by the American College of Rheumatology (ACR) and the international consensus on ANA patterns (ICAP) the gold standard for the screening of anti-nuclear antibodies (ANA). As conventional IIF is labor intensive, time-consuming, subjective, and poorly standardized, there have been ongoing efforts to improve the standardization of reagents and to develop automated platforms for assay incubation, microscopy, and evaluation. In this study, the workflow and performance characteristics of a fully automated ANA IIF system (Sprinter XL, EUROPattern Suite, IFA 40: HEp-20-10 cells) were compared to a manual approach using visual microscopy with a filter device for single-well titration and to technologist reading. The Sprinter/EUROPattern system enabled the processing of large daily workload cohorts in less than 8 h and the reduction of labor hands-on time by more than 4 h. Regarding the discrimination of positive from negative samples, the overall agreement of the EUROPattern software with technologist reading was higher (95.6%) than when compared to the current method (89.4%). Moreover, the software was consistent with technologist reading in 80.6–97.5% of patterns and 71.0–93.8% of titers. In conclusion, the Sprinter/EUROPattern system provides substantial labor savings and good concordance with technologist ANA IIF microscopy, thus increasing standardization, laboratory efficiency, and removing subjectivity.

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.

Association of anti-Ro52, anti-Ro60 and anti-La antibodies with diagnostic, clinical and laboratory features in a referral hospital in Jerez, Spain

OBJECTIVE

Several antibodies have proven to be useful in autoimmune diseases, as markers for diagnosis, prognosis or clinical manifestations. Our objective was to evaluate the diagnosis and manifestations associated for antibodies anti-Ro52, anti-Ro60 and anti-La at a referral hospital in Spain.

METHODS

We retrospectively analyzed the antigenic specificities of the consecutive samples submitted to the Immunology Unit for antinuclear antibody screening between 2002 and 2012. We included patients with more than one positive sample for some of the autoantibodies anti-Ro52, anti-Ro60 or anti-La. We also reviewed diagnosis, clinical and laboratory features. As dependent variable we evaluated possible combinations of anti-Ro52, anti-Ro60 and anti-La.

RESULTS

322 patients, 91% females, were studied (age 44.3±15.51 years). The most frequent diagnosis was Sjögren's syndrome (40.06%) and systemic lupus erythematosus (SLE) (36.6%). The most prevalent pattern by indirect immunofluorescence was the fine speckled (69.9%). Anti-Ro52+/anti-Ro60+/anti-La+ combination was positively associated with fine speckled pattern (p: 0.001) and negatively with homogeneous (p: 0.016) and cytoplasmic pattern (p: 0.002). Isolated anti-Ro52+ was negatively associated with fine speckled pattern (p<0.001) and positively with the cytoplasmic one (p<0.001). The main positive associations with clinical symptoms were xerostomia and xerophthalmia with anti-Ro52+/anti-Ro60+/anti-La+ (p<0.001), oral ulcers with anti-Ro52+/anti-Ro60+/anti-La- (p: 0.002) and alopecia with anti-Ro52-/anti-Ro60+/anti-La- (p: 0.003). Negative associations were xerophthalmia and photosensitivity with anti-Ro52+/anti-Ro60-/anti-La- (p: 0.003). Laboratory positive associations were hypergammaglobulinemia with anti-Ro52+/anti-Ro60+/anti-La+ (p: 0.003), and hypocomplementemia with anti-Ro52-/anti-Ro60+/anti-La- (p: 0.003). Leucopenia was negatively associated with anti-Ro52+/anti-Ro60-/anti-La- (p: 0.003).

CONCLUSION

Our study found significant relationships between clinical and laboratory manifestations with different patterns of antibodies to anti-Ro52, anti-Ro60 and anti-La. The combination of antibodies might be clinically useful due to prognostic and therapeutic implications.

Autoantibody Detection Using Multiplex Technologies

Measurement of multiple antibodies has been possible for years using labor-intensive methods such as counterimmunoelectrophoresis and radioimmunoprecipitation. Recently, simpler methods that are more practical for routine analysis, often described as multiplex technologies, have been introduced. One common technique, the line assay, uses nitrocellulose strips that are precoated at different locations with more than a dozen recombinant proteins or peptides. Detection of results may be performed visually or with scanning instrumentation. A second technique uses families of polystyrene beads that are dyed to establish a unique identity; each bead type is then coated with a specific affinity-purified or recombinant protein. Detection is performed by flow cytometry. There have been multiple descriptions of the use of these techniques for measuring antibodies associated with the antinuclear antibody screen. More recent reports describe applications to antibodies associated with hypothyroidism, ANCA, anti-phospholipid syndrome, and celiac disease. This review summarizes the work that has been performed to date and examines the potential benefits of multiplexing to both the laboratory and the physician.

The prevalence of antinuclear antibodies in patients with sarcoidosis

Introduction. Sarcoidosis, which is a chronic inflammatory granulomatous disease, can mimic different rheumatologic diseases including connective tissue diseases. Antinuclear antibodies are the markers used for connective tissue diseases. Aim. To determine antinuclear antibody frequency and any possible correlation with clinical and laboratory data in sarcoidosis patients. Material and Method. Forty-two sarcoidosis patients, 45 rheumatoid arthritis patients, and 45 healthy volunteers who were followed up in rheumatology outpatient clinic were included in this study. Demographic, clinical, serological, and radiological data of all patients were recorded. Antinuclear antibodies were determined with indirect immunofluorescent method and 1/100 titration was accepted as positive. The cases that were ANA positive were evaluated with immunoblot method. Results. Average age of the 42 patients (10 males) with sarcoidosis was 45.2 (20–70 years), and average disease duration was 3.5 years. ANA positivity was detected in 12 (28.5%) patients with sarcoidosis (1/100 in 10 patients, 1/320 in two patients), in 19 of RA patients (42.2%), and in two of healthy volunteers in low titer (P < 0.001). In the subgroup analysis made by immunblot test, one patient had anticentromere antibody, one had anti-Ro antibody, one had anti-Scl-70 antibody, one had anti-dsDNA antibody, and eight patients were negative. The two patients who had anticentromere and anti-Scl-70 antibodies had also Sjögren's syndrome and scleroderma diagnosis, respectively. Discussion. The prevalence of ANA in patients with sarcoidosis was found to be significantly higher than healthy control group and lower than RA patients. This result shows that ANA may have an important role in the pathogenesis of sarcoidosis and also could be important in revealing the overlap syndromes of sarcoidosis-connective tissue diseases. Further studies with larger series are necessary in this subject.

Determination of Anti-nuclear Antibody Pattern Distribution and Clinical Relationship

Background and Objectives: Autoantibodies are immunglobulins occurred directly against autoantigens that are known as endogen antigens. Autoimmune disease is an occasion that the body begins a fight against its own cells and tissues. The antibodies that are created by the body against its own cell nuclei are called as anti-nuclear antibodies (ANA), and one of the methods used for detection and pattern of ANA is indirect immunofluorescence test (IIF). In the present study, it was aimed to determine the rate of ANA positivity and patterns of the positive specimens, and to investigate the relationship between ANA positivity and diseases in patients.

Methods: ANA test results of a total of 3127 patients admitted during March 2010 to December 2012 were evaluated retrospectively. ANA test (HEp 20-10, EUROIMMUN, Germany) was used in dilution of 1:100 in IIF test.

Results: A total of 494 (15.8%) resulted as ANA positive. ANA positivity rate was significantly higher in female patients than the male ones (p<0.001). The most frequent ANA patterns were coarse speckled pattern (154 patients, 31.2%), nucleolar pattern (89 patients, 18.0%), fine speckled pattern (57 patients, 11.5%), and speckled pattern (48 patients, 9.7%). ANA positivity was most commonly determined in rheumatoid arthritis (RA) (42 patients, 8.5%), systemic lupus erythematosus (SLE) (29 patients, 5.9%), and rheumatoid vasculitis (RV) (28 patients, 5.7%). The most frequent symptoms or findings were joint pain (127 patients, 26.0%) and anemia (28 patients, 5.7%). ANA positivity rates were found to be significantly higher in patients with RA (p<0.001), with SLE (p<0.001), and with Raynaud phenomenon (p=0.001) in comparison to the controls. Amongst the most frequent diseases evaluated, no significant differences were found between the control groups and the groups of RV (p=0.089), multiple sclerosis (p=0.374), and Sjögren syndrome (p=0.311) in terms of ANA positivity rates.

Conclusions: The present study is the first study reporting the positivity rate and distribution of ANA in Bolu located in northwestern Turkey. Information about the pattern types and the distribution of the patterns according to the diseases and symptoms contribute in diagnosis of autoimmune diseases. It is observed that clinical diagnosis has been supported significantly by ANA test according to data of our study.

Current state of diagnostic technologies in the autoimmunology laboratory

The methods for detecting and measuring autoantibodies have evolved markedly in recent years, encompassing three generations of analytical technologies. Many different immunoassay methods have been developed and used for research and laboratory practice purposes, from the early conventional (or monoplex) analytical methods able to detect single autoantibodies to the more recent multiplex platforms that can quantify tens of molecules. Although it has been in use for over 50 years, indirect immunofluorescence remains the standard method for research on many types of autoantibodies, due to its characteristics of diagnostic sensitivity and also to recent technological innovations which permit it a greater level of automation and standardization. The recent multiplex immunometric methods, with varying levels of automation, present characteristics of higher diagnostic accuracy, but are not yet widely diffused in autoimmunology laboratories due to the limited number of autoantibodies that are detectable, and due to the high cost of reagents and systems. Technological advancement in autoimmunology continues to evolve rapidly, and in the coming years new proteomic techniques will be able to radically change the approach to diagnostics and possibly also clinical treatment of autoimmune diseases. The scope of this review is to update the state of the art of technologies and methods for the measurement of autoantibodies, with special reference to innovations in indirect immunofluorescence and in multiple proteomic methods.

Evaluation of ENA-6 Profile by ELISA Immunoassay in Patients with Systemic Lupus Erythematodes

Autoimmune diseases occur in 3−5% of the population. Study included 30 patients with clinically diagnosed SLE and 30 healthy controls (American college of Rheumatology, 1997). SLE was diagnosed according to criteria issued in 1997 by the American College of Rheumatology (ACR). The aim of this study was to evaluate concentration values of each antigen of ENA-6 profile in SLE, to investigate possible correlation between the concentration of Sm antibodies and CIC, and to test their use as possible immunobiological markers in SLE. Furthermore, the aim of our study was to determine whether there is a correlation between Sm antibodies and CIC and SLE activity. The results revealed that all of these ENA-6 and Sm antibodies as biomarkers complement diagnoses of active SLE but their use as solo markers does not allow classifying patients with SLE. Our study has shown that based on calculations from ROC curves, Sm/RNP was clearly a very important marker for diagnosis of SLE (cut off ≥ 9.56 EU, AUC 0,942). The high incidence of Scl-70 (10%) reactivity suggests that ELISA monitoring of this antibody produces more false positive results than other multiplex assay. An important conclusion that can be drawn from the results of our study is that laboratory tests are no more effective than clinical examination for detecting disease relapse, but are helpful in the confirmation of SLE activity.

A highly versatile microscope imaging technology platform for the multiplex real-time detection of biomolecules and autoimmune antibodies

The analysis of different biomolecules is of prime importance for life science research and medical diagnostics. Due to the discovery of new molecules and new emerging bioanalytical problems, there is an ongoing demand for a technology platform that provides a broad range of assays with a user-friendly flexibility and rapid adaptability to new applications. Here we describe a highly versatile microscopy platform, VideoScan, for the rapid and simultaneous analysis of various assay formats based on fluorescence microscopic detection. The technological design is equally suitable for assays in solution, microbead-based assays and cell pattern recognition. The multiplex real-time capability for tracking of changes under dynamic heating conditions makes it a useful tool for PCR applications and nucleic acid hybridization, enabling kinetic data acquisition impossible to obtain by other technologies using endpoint detection. The paper discusses the technological principle of the platform regarding data acquisition and processing. Microbead-based and solution applications for the detection of diverse biomolecules, including antigens, antibodies, peptides, oligonucleotides and amplicons in small reaction volumes, are presented together with a high-content detection of autoimmune antibodies using a HEp-2 cell assay. Its adaptiveness and versatility gives VideoScan a competitive edge over other bioanalytical technologies.

Antinuclear antibodies as ancillary markers in primary biliary cirrhosis

Antimitochondrial antibodies are the serological hallmark of primary biliary cirrhosis (PBC). Besides antimitochondrial antibodies, the autoantibody profile of PBC includes antinuclear antibodies (ANA) which are detectable by indirect immunofluorescence in up to 50% of PBC patients. Two immunofluorescence patterns are considered 'PBC-specific': the multiple nuclear dots and rim-like/membranous patterns. The target antigens of the multiple nuclear dots pattern have been identified as Sp100 and promyelocytic leukemia protein, whereas the rim-like/membranous pattern is given by autoantibodies recognizing multiple proteins such as gp210, nucleoporin p62 and the lamin B receptor. Other ANA, especially those already known in the rheumatological setting, such as anticentromere, anti-SSA/Ro and anti-dsDNA antibodies, can be frequently found in PBC, often coexisting in the same patient. In this article, we will report on recent progress in the antigenic characterization of ANA in PBC, their detection with both traditional assays and Western blot/ELISA with molecularly defined nuclear antigens, and we will discuss their clinical significance.

Comparison of indirect immunofluorescence and multiplex antinuclear antibody screening in systemic sclerosis

Indirect immunofluorescence antinuclear antibodies (IIF-ANA) are detected in approximately 90% of scleroderma patients, and the staining pattern correlates with scleroderma-specific antibody subsets. Solid-phase ANA assays that are dependent on multiplex bead technology (MULTIPLEX-ANA) are replacing immunofluorescence in many commercial labs; however, performance of these assays has not been compared to IIF-ANA in scleroderma. The purpose of this study was to evaluate whether a proportion of scleroderma patients have negative testing on MULTIPLEX-ANA assays and demonstrate whether negative MULTIPLEX-ANA is associated with particular scleroderma-specific autoantibodies. A retrospective chart review was completed on all 238 scleroderma patients evaluated in the Georgetown scleroderma clinic between June 1, 2008 and May 31, 2009. Autoantibody results, demographics, and scleroderma features were collected. Data were analyzed using unpaired t test and Mann-Whitney U test for continuous variables, and Fisher's exact test for dichotomous variables. Simple kappa coefficient was used to measure the level of agreement between MULTIPLEX-ANA and IIF-ANA results. Two-tailed p values <0.05 were considered significant. MULTIPLEX-ANA testing was available in 57 patients and only 29 (51%) tested positive. In contrast, IIF-ANA was positive in 91% of these patients. Using simple kappa coefficient, there was a good agreement between the MULTIPLEX-ANA, and presence of Scl70, RNP, and centromere antibodies (0.76; 95% CI 0.59, 0.92), but there was no agreement between MULTIPLEX-ANA and presence of other IIF-ANA patterns including nucleolar ANA (-0.40; 95% CI -0.64, -0.16). Because RNA polymerase III and nucleolar antibodies are seen in 43% of the entire scleroderma population, we are concerned that these false-negative tests could result in delays in referral and diagnosis. Until the MULTIPLEX-ANA assays can be modified to include the antigens for RNA polymerase III and the nucleolar ANA subsets, IIF-ANA remains the recommended screening test for ANA in suspected scleroderma.

Sm peptides in differentiation of autoimmune diseases

Systemic lupus erythematosus (SLE) and related diseases are characterized by circulating autoantibodies to defined intracellular targets. Among the earliest identified autoantibodies were those directed to components of U2-U6 small nuclear ribonucleoproteins (snRNPs) known as Smith (Sm) antigen, which are highly specific for SLE. The Sm-antigen is composed of at least nine different polypeptides with molecular weights ranging from 9 to 29.5 kDa (B (B1, 28 kDa), B' (B2, 29 kDa), N (B3, 29.5 kDa), D1 (16 kDa), D2 (16.5 kDa), D3 (18 kDa), E (12 kDa), F (11 kDa), and G (9 kDa)). All of the nine core proteins, but most frequently the B and D polypeptides, are targets of the anti-Sm autoimmune response. However, since SmBB' and U1 specific RNPs share the cross-reactive epitope motif PPPGMRPP, SmD is regarded as the most SLE specific Sm-antigen. It has been shown that the polypeptides D1, D3, and BB' contain symmetrical dimethylarginine, constituting a major autoepitope within the C-terminus of SmD1 and SmD3. Several synthetic peptides have been used for the detection of anti-Sm antibodies and thus for the diagnosis of SLE. Anti-Sm antibodies have been reported to occur later than other SLE associated autoantibodies and, on average, around 1 year before the clinical onset of SLE. The present review provides a comprehensive summary on the history of anti-Sm antibodies and their use as biochemical tools to study cellular processes and as biomarker in the diagnosis of SLE. Additionally, a meta-analysis focused on recent data analyzes the prevalence of anti-Sm antibodies in SLE.

Determination of cut-off titers and agreement between immunofluorescence and immunoblotting methods for detecting antinuclear antibodies in children

Detection of antinuclear antibodies (ANA) is a diagnostic adjunct in patients with suspected autoimmune connective tissue diseases, and various detection methods are in use. The aim of this study was to analyze the agreement between the ANA immunoflourescence (IF) and immunoblotting (IB) methods and determine cut-off for children subjects in a laboratory setting. We evaluated 729 serum samples that were analyzed by both ANA IF and IB. The results were evaluated by chi(2) test and, for agreement, kappa index was used. Frequencies determined for both 1:40-1:100 cut-off titers of ANA IF in relation to IB testing supported the idea that 1:100 starting dilution should be recommended in children subjects for ANA IF method and antigen specific immunoblot testing was needed, especially for some of the ANA IF negative samples. Agreement between the two methods, especially with homogenous, granular, and nucleolar ANA IF patterns, was statistically significant.

Anti-Scl-70 (topo-I) antibodies in SLE: Myth or reality?

Autoantibodies to topoisomerase I (topo-I, also referred to as Scl-70, ATA) have historically been considered a specific marker for systemic sclerosis (SSc). Although found in approximately 20% of SSc sera, other evidence indicated that ATA also occur in up to 25% of systemic lupus erythematosus (SLE). Given that SLE is approximately 100 times more prevalent than SSc, the number of ATA positive SLE patients is at least 2-3 orders of magnitude greater than the prevalence of ATA in SSc. These observations have raised questions about the disease specificity and clinical value of ATA. Therefore, our objective was to analyse the prevalence of ATA in different disease conditions with a special focus on SLE employing a systematic literature review (meta-analysis) in combination with our experimental investigations.

Detection of antinuclear antibodies by the Inno-Lia ANA update test in canine systemic rheumatic disease

BACKGROUND

Certain systemic autoimmune diseases in dogs are characterized by high titers of circulating antinuclear antibodies (ANA), which can be demonstrated by indirect immunofluorescence (IIF). In an earlier study of IIF-ANA-positive dogs, the Ouchterlony double immunodiffusion (DID) test was used to identify specific autoantibodies. The DID test has largely been replaced with line blot tests in human diagnostic settings.

OBJECTIVE

The objective of this study was to investigate whether the line blot assay Inno-Lia ANA update test is a useful tool in demonstrating ANA specificities in canine patients with previously diagnosed IIF-ANA-positive rheumatic disorders.

METHODS

Serum samples from 3 clinically healthy control dogs and 20 canine patients with clinical signs of systemic rheumatic disease and documented positive results for IIF-ANA and DID tests were included in the study. The Inno-Lia ANA update assay was performed with an anti-canine detection antibody.

RESULTS

Six serum samples that had DID positivity with anti-spliceosomal small nuclear ribonucleoproteins (snRNP) reactivity showed reactivity to multiple snRNP proteins in the Inno-Lia test. Samples from 2 dogs that had other types of DID positivity also had clear SmB reactivity and 1 had weak reactivity to RNP-70K. The other serum samples, including controls, were negative.

CONCLUSIONS

Using the Inno-Lia ANA update test, multiple snRNP specificities were demonstrated in some canine patients with autoimmune rheumatic disorders. Other canine autoantibodies may exist that are not detected by this test. Further studies are necessary to characterize the target antigen(s) of these remaining autoantibodies in canine sera.

Novel method for quantitative ANA measurement using near-infrared imaging

Antinuclear antibodies (ANA) have been detected in patients with systemic rheumatic diseases and are used in the screening and/or diagnosis of autoimmunity in patients as well as mouse models of systemic autoimmunity. Indirect immunofluorescence (IIF) on HEp-2 cells is the gold standard for ANA screening. However, its usefulness is limited in diagnosis, prognosis and monitoring of disease activity due to the lack of standardization in performing the technique, subjectivity in interpreting the results and the fact that it is only semi-quantitative. Various immunological techniques have been developed in an attempt to improve upon the method to quantify ANA, including enzyme-linked immunosorbent assays (ELISAs), line immunoassays (LIAs), multiplexed bead immunoassays and IIF on substrates other than HEp-2 cells. Yet IIF on HEp-2 cells remains the most common screening method for ANA. In this study, we describe a simple quantitative method to detect ANA which combines IIF on HEp-2 coated slides with analysis using a near-infrared imaging (NII) system. Using NII to determine ANA titer, 86.5% (32 of 37) of the titers for human patient samples were within 2 dilutions of those determined by IIF, which is the acceptable range for proficiency testing. Combining an initial screening for nuclear staining using microscopy with titration by NII resulted in 97.3% (36 of 37) of the titers detected to be within two dilutions of those determined by IIF. The NII method for quantitative ANA measurements using serum from both patients and mice with autoimmunity provides a fast, relatively simple, objective, sensitive and reproducible assay, which could easily be standardized for comparison between laboratories.

Antibodies to SS-A/Ro-52kD and centromere in autoimmune liver disease: a clue to diagnosis and prognosis of primary biliary cirrhosis

BACKGROUND

Primary biliary cirrhosis (PBC) may be associated with various rheumatological disorders.

AIM

To investigate the frequency and significance of 'rheumatological' antinuclear antibodies in the field of autoimmune chronic liver disease, with special regard to PBC.

METHODS

We studied 105 patients with PBC, 162 autoimmune liver disease controls (type 1 and 2 autoimmune hepatitis, primary sclerosing cholangitis), 30 systemic lupus erythematosus and 50 blood donors. Sera were tested for the presence of antibodies to extractable nuclear antigens (anti-ENA) by counterimmunoelectrophoresis, enzyme-linked and immunoblot (IB) assay, and for the presence of anti-centromere antibodies (ACA) by indirect immunofluorescence on HEp-2 cells and IB.

RESULTS

The overall prevalence of IB-detected anti-ENA in PBC (30%) was higher than in type 1 autoimmune hepatitis (2.5%, P < 0.0001), type 2 autoimmune hepatitis (0%, P < 0.0001) and primary sclerosing cholangitis (11.5%, P = 0.006) and lower than in systemic lupus erythematosus (53%, P = 0.03). The most frequent anti-ENA reactivity in PBC was anti-SSA/Ro-52kD (28%). ACA were detected by IB in 21% PBC patients and never in the other subjects (P < 0.0001). Anti-SS-A/Ro/52kD positive PBC patients had at the time of diagnosis a more advanced histological stage (P = 0.01) and higher serum levels of bilirubin (P = 0.01) and IgM (P = 0.03) compared with negative ones.

CONCLUSIONS

In the autoimmune liver disease setting, anti-SS-A/Ro-52kD and ACA have a high specificity for PBC and can thus be of diagnostic relevance in anti-mitochondrial antibodies negative cases. If confirmed in further studies with adequate follow-up, anti-SS-A/Ro-52kD antibodies might identify PBC patients with a more advanced and active disease.

Recent advances in diagnostic technologies and their impact in autoimmune diseases

Conventional immunological methods for the detection of serum autoantibodies have been an essential tool for the diagnosis of autoimmune diseases for 40 years: in the last decade autoantibody tests have become accepted criteria for the diagnosis and classification of the main systemic and organ-specific autoimmune diseases. The high degree of purification reached by the autoantigens used in these methods has allowed high diagnostic sensitivity and specificity, especially in the case of some new autoantibodies of particular clinical significance, such as anti-nucleosome, anti-transglutaminase, anti-TSH receptor and anti-citrullinated protein autoantibodies. In the last 5 years the advent of proteomic technology, which allows the simultaneous measurement of a number of autoantibodies (multiplexing), has opened up new horizons in the diagnosis of autoimmune diseases. Multiplexing is particularly interesting for clinical laboratories, for organisational, logistical/managerial, physiopathological and research reasons. The emerging technologies are represented by systems based on planar or non-planar (suspension) arrays: the latter include methods which use addressable microbeads or nanobarcoded particles. Within a few years, the new methods will allow testing of individual autoantibody profiles, which will probably improve understanding of the physiopathology of autoimmunity, allow early diagnosis (due to the predictive value of autoantibodies), and drive the diffusion of antigen-specific therapies in autoimmune diseases.