Anti-dsDNA: choice of assay in relation to clinical value

Drug History and SLE Laboratory Findings Among Iraqi Patients: A Hospital-Based Study

Background and Aims

Systemic lupus erythematosus (SLE) is a recurrent and remitting autoimmune disease that affects many organ systems. It is more common in women of reproductive age, with a 9:1 female preponderance. Due to the lack of data from developing countries, our study aims to provide comprehensive insights into the drug history and SLE laboratory findings among Iraqi patients.

Methodology

It is a cross-sectional study at the Baghdad Medical Complex in Iraq. All SLE patients who attended the outpatient clinic between September and December 2022 were included. The patients included those who came for follow-up, deterioration of their symptoms, or a first-time diagnosis.

Results

SLE is much more prevalent among female patients. The ratio of female and male patients in our study was 19:1. This disease is more prevalent in the reproductive age group, with the mean age of our patients being 34 years, although the range spans from 15 to 85 years. The most prevalent signs and symptoms among the patients were photosensitivity (79.5%), hair loss (74%), and malar rash (72.5%). Most patients had positive antinuclear antibodies and anti-double-stranded DNA antibodies, with 73.5% and 65% testing positive, respectively.

Conclusion

In conclusion, this study represents an important step in exploring SLE within Iraq, providing invaluable insights into its management and laboratory findings. The findings contribute to the global understanding of SLE. This study underscores the significance of Iraq's genetic backgrounds and environmental conditions, which are different from those of other countries, in the process of enhancing the global medical literature and expanding our understanding of SLE patterns around the world.

Issues in autoantibody tests used in the classification criteria for autoimmune rheumatic diseases: the laboratory autoimmunologist's perspective

Classification criteria of autoimmune rheumatic diseases are an important means to define homogenous groups of patients that can be compared across studies for clinical trials and research purposes. The measurement of autoantibodies is a relevant aspect in the definition of classification criteria, with a significant weight in the scores necessary to classify patients with autoimmune rheumatic diseases. The impact of autoantibodies has gradually increased over the years, contributing to the evolution and improvement of the classification criteria. However, these criteria often do not take into consideration how autoantibodies are measured, i.e. differences in diagnostic accuracy of the methods. This is a critical point especially when obsolete analytical methods that are no longer used in many clinical laboratories are taken into consideration. In this review we have critically examined assays and methods for the determination of autoantibodies that are (or could be) included among the classification criteria of autoimmune rheumatic diseases in light of more recent evidence and technology evolution.

Comparative analysis of contemporary anti-double stranded DNA antibody assays for systemic lupus erythematosus

Objective

Elevated double-stranded DNA (dsDNA) antibody levels in blood serum are considered a disease-specific marker in systemic lupus erythematosus (SLE), correlate with disease activity and the incidence of lupus nephritis, and can be detected in up to 86% of all SLE cases. Despite the high clinical relevance, the variety of dsDNA antibody testing methods with heterogenous performance in clinical use remains challenging. This study is the first to prospectively investigate the performance of two of today's most commonly applied anti-dsDNA testing methods head-to-head under real-world conditions, as well as their correlation with other clinical and serological disease parameters in SLE patients.

Methods

In this prospective study, all SLE patients undergoing treatment at the Department of Rheumatology at the University Hospital Bonn within a 13-months period (n=41) and control patients without connective-tissue disease (n=51) were consecutively enrolled and examined. For all study participants' serum samples both anti-dsDNA-NcX enzyme-linked immunoassay testing EUROIMMUN, Luebeck, Germany) and the fluorescence immunoassay ELiA dsDNA (Thermo Fisher Scientific, Waltham, USA) were performed. In addition, demographic data, further laboratory values and disease activity parameters were recorded. Clinical disease activity was assessed by SLEDAI-2K.

Results

Both assays showed high specificity (anti-dsDNA-NcX ELISA: 0.9, ELiA dsDNA: 0.959), but there were notable differences in sensitivity (anti-dsDNA-NcX ELISA: 0.51, ELiA dsDNA: 0.38). Pearsons's correlation yielded a positive correlation between anti-dsDNA concentrations and CRP concentrations for the anti-dsDNA-NcX ELISA (R=0.22; p=0.038) and a mild-to-moderate inverse correlation between concentrations of anti-dsDNA and complement C4 for the ELiA dsDNA test (R=-0.22; p=0.045) when SLE and control patients were considered together. Other than, no significant correlation between anti-dsDNA concentrations and clinical or laboratory findings was found for either test procedure.

Conclusion

Both anti-dsDNA antibody assays represent reliable examination methods with high specificity for the diagnosis of SLE that fulfill EULAR/ACR requirements. However, the anti-dsDNA-NcX ELISA showed superior sensitivity and significant correlation with disease activity (as measured by CRP concentrations).

Laboratory evaluation of anti-dsDNA antibodies

Antibodies to dsDNA are an important laboratory parameter for diagnosis, monitoring and classification of systemic lupus erythematosus (SLE). In clinical laboratories, several techniques are used to detect and quantify anti-dsDNA antibodies. Each technique has its advantages and disadvantages regarding sensitivity, specificity, avidity and assay procedure. Assays differ with respect to the antigen source (native versus synthetic versus molecular biological) used and the way the antigen is presented (e.g. in solution, covalently linked to a solid phase,…). Consequently, correlation between assays can be poor and standardization of anti-dsDNA antibody tests is challenging. We here provide an overview of the currently available anti-dsDNA tests frequently used in clinical laboratories [Crithidiae luciliae immunofluorescence test (CLIFT), Enzyme linked immune sorbent assay (ELISA), fluoroenzyme immunoassay (FEIA), chemiluminescence (CIA), multiplexed bead-based assays and Farr-RIA] and their performance characteristics. From this literature study, we concluded that performance characteristics differ between assays. Often, a combination of techniques is necessary for the best result interpretation.

Monoplex and multiplex immunoassays: approval, advancements, and alternatives

Immunoassays are a powerful diagnostic tool and are widely used for the quantification of proteins and biomolecules in medical diagnosis and research. Enzyme-linked immunosorbent assay (ELISA) is the most commonly used immunoassay format and allows the detection of biomarkers at a very low concentration. The diagnostic platforms such as enzyme immunoassay (EIA), chemiluminescence (CL) assay, polymerase chain reaction (PCR), flow cytometry (FC), and mass spectrometry (MS) have been used to identify molecular biomarkers. However, these diagnostic tools requiring expensive equipment, long testing time, and qualified personnel that is not always available in small local hospitals with limited resources. The lateral flow immunoassay (LFIA) platform was developed for rapidly obtaining laboratory results and to make urgent decisions in emergency medicine, as well as the recently introduced concept of testing at the site of care (point-of-care, POC). The simultaneous measurement of different substances from a single sample called multiplex assays have become increasingly significant for in vitro quantification of multiple analytes in a single sample, thereby minimising cost, time, and volume. In multiplex immunoassays, the ligands are immobilized either in planar format (flat surface) or on microspheres in suspension that binds to target analytes in sample. The multiplex technology has established itself in proteomic networks and pathways, validation of genomic discoveries, and in the development of clinical biomarkers. In the present review article, various types of monoplex/simplex and complex/multiplex immunoassays have been analysed that are increasingly being applied in laboratory medicine. Also, some advantages and disadvantages of these multiplex assays have also been included such as experimental animals, in vitro tests using cell lines and tissue samples, 3-dimensional modelling and bioprinting, in silico tests, organ-on-chip, and computer modelling.

Autoimmunity and SLE: Factual and Semantic Evidence-Based Critical Analyses of Definitions, Etiology, and Pathogenesis

One cannot discuss anti-dsDNA antibodies and lupus nephritis without discussing the nature of Systemic lupus erythematosus (SLE). SLE is insistently described as a prototype autoimmune syndrome, with anti-dsDNA antibodies as a central biomarker and a pathogenic factor. The two entities, "SLE" and "The Anti-dsDNA Antibody," have been linked in previous and contemporary studies although serious criticism to this mutual linkage have been raised: Anti-dsDNA antibodies were first described in bacterial infections and not in SLE; later in SLE, viral and parasitic infections and in malignancies. An increasing number of studies on classification criteria for SLE have been published in the aftermath of the canonical 1982 American College of Rheumatology SLE classification sets of criteria. Considering these studies, it is surprising to observe a nearby complete absence of fundamental critical/theoretical discussions aimed to explain how and why the classification criteria are linked in context of etiology, pathogenicity, or biology. This study is an attempt to prioritize critical comments on the contemporary definition and classification of SLE and of anti-dsDNA antibodies in context of lupus nephritis. Epidemiology, etiology, pathogenesis, and measures of therapy efficacy are implemented as problems in the present discussion. In order to understand whether or not disparate clinical SLE phenotypes are useful to determine its basic biological processes accounting for the syndrome is problematic. A central problem is discussed on whether the clinical role of anti-dsDNA antibodies from principal reasons can be accepted as a biomarker for SLE without clarifying what we define as an anti-dsDNA antibody, and in which biologic contexts the antibodies appear. In sum, this study is an attempt to bring to the forum critical comments on the contemporary definition and classification of SLE, lupus nephritis and anti-dsDNA antibodies. Four concise hypotheses are suggested for future science at the end of this analytical study.

Review: immunoassays in DNA damage and instability detection

The review includes information on the current state of knowledge of immunometric methods with emphasis on the possibility of deoxyribonucleic acid (DNA) damage detection. Beginning with basic immunoassay enzyme-linked immunosorbent assay (ELISA), this review describes methods such as tyramide signal amplification (TSA), enhanced polymer one-step staining (EPOS), and time resolved amplified cryptate emission (TRACE) as improvements of ELISA's developed over time to obtain more accurate results. In the second part of the review, surface plasmon resonance (SPR) and quantum dots (QDs) are presented as the newest outlooks in the context of immunoanalysis of biological material and molecular studies. The aim of this review is to briefly present immunoassays with emphasis on DNA damage detection; therefore, the types of methods are listed and described, types of signal indicators, basic definitions such as antigen and antibody are given. Every method is considered with an exemplary application focusing on DNA studies, DNA damage and instability detection.

Clinical evaluation of total and high-avidity anti-dsDNA antibody assays for the diagnosis of systemic lupus erythematosus

Background

This study evaluated the diagnostic performances of total and high-avidity (HA) anti-dsDNA enzyme immunoassays (EIA) in Chinese systemic lupus erythematosus (SLE) patients.

Methods

A total of 410 serum samples from 217 SLE patients, 54 patients with other systemic autoimmune diseases, and 139 healthy subjects were tested on total and HA anti-dsDNA EIA, as well as three commercial in vitro diagnostic kits: BioPlex 2200 ANA Screen, Kallestad anti-dsDNA EIA, and Crithidia Lucilae IFA. The disease activities of SLE patients were assessed using the modified SLE Disease Activity Index. The diagnostic performances of each assay were analyzed using Analyse-it software.

Results

The diagnostic performances of the total and HA anti-dsDNA EIA kits were comparable to other commercially available in vitro diagnostic assays. Receiver operating characteristic curve analysis demonstrated an area under the curve ranging from 0.85 to 0.89, with the total anti-dsDNA kit demonstrating the highest sensitivity and the HA kit showing higher specificity. An overall agreement of >90% was observed between the total and HA anti-dsDNA EIA kits and commercially available quantitative anti-dsDNA kits. The ratio of HA to total anti-dsDNA antibody was significantly higher among SLE patients with active disease status and/or kidney damage. All assays exhibited a significant correlation with disease activity and multiple clinical manifestations.

Conclusions

While the clinical performances of various anti-dsDNA assays showed adequate agreements, the BioPlex 2200 anti-dsDNA assay demonstrated the highest positive likelihood ratio and odds ratio. The HA anti-dsDNA EIA kit in association with the total anti-dsDNA kit provided superior performance in SLE diagnosis and monitoring disease activity.

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.

The anti-DNA antibody: origin and impact, dogmas and controversies

The inclusion of 'the anti-DNA antibody' by the ACR and the Systemic Lupus International Collaborating Clinics (SLICC) as a criterion for systemic lupus erythematosus does not convey the diverse origins of these antibodies, whether their production is transient or persistent (which is heavily influenced by the nature of the inducing antigens), the specificities exerted by these antibodies or their clinical impact-or lack thereof. A substantial amount of data not considered in clinical medicine could be added from basic immunology evidence, which could change the paradigms linked to what 'the anti-DNA antibody' is, in a pathogenic, classification or diagnostic context.

Anti-C1q antibodies as a follow-up marker in SLE patients

In cross-sectional studies autoantibodies against complement C1q (anti-C1q) were found to be highly associated with active lupus nephritis. The aim of this retrospective study was to determine the value of anti-C1q as follow-up marker of disease activity and renal involvement in patients with systemic lupus erythematosus (SLE). Fifty-two patients with SLE and a minimum of three anti-C1q measurements during follow-up were analyzed. Anti-C1q levels correlated with global disease activity scores. In subgroup analyses, patients without renal involvement did not show a significant correlation between anti-C1q levels and disease activity. In contrast, in patients with renal involvement, anti-C1q levels correlated well with global disease activity. In addition, a positive correlation with the urine protein-to-creatinine ratio and anti-dsDNA antibody levels as well as a negative correlation with complement levels was observed. Anti-C1q antibodies were found to strongly correlate with parameters of SLE disease activity during follow-up, in particular with regard to renal involvement.

Anti-ribosomal P protein: a novel antibody in autoimmune hepatitis

BACKGROUND

Autoantibodies to ribosomal P proteins (anti-rib P) are specific serological markers for systemic lupus erythematosus (SLE) and are associated with liver involvement in this disease. The similarity in autoimmune background between autoimmune hepatitis (AIH) and SLE-associated hepatitis raises the possibility that anti-rib P antibodies might also have relevance in AIH.

AIMS

To evaluate the frequency and clinical significance of anti-rib P antibodies in a large AIH cohort.

METHODS

Sera obtained at diagnosis of 96 AIH patients and of 82 healthy controls were tested for IgG anti-ribosomal P protein by ELISA. All of the sera were also screened for other lupus-specific autoantibodies, three patients with the presence of anti-dsDNA (n = 1) and anti-Sm (n = 2) were excluded.

RESULTS

Moderate to high titres (>40 U) of anti-rib P antibody were found in 9.7% (9/93) of the AIH patients and none of the controls (P = 0.003). At presentation, AIH patients with and without anti-rib P antibodies had similar demographic/clinical features, including the frequency of cirrhosis (44.4 vs. 28.5%, P = 0.44), hepatic laboratorial findings (P > 0.05). Importantly, at the final observation (follow-up period 10.2 ± 4.9 years), the AIH patients with anti-rib P had a significantly higher frequency of cirrhosis compared with the negative group (100 vs. 60%, P = 0.04).

CONCLUSION

The novel demonstration of anti-rib P in AIH patients without clinical or laboratory evidence of SLE suggests a common underlying mechanism targeting the liver in these two diseases. In addition, this antibody appears to predict the patients with worse AIH prognoses.

The effect of methotrexate on improving serological abnormalities of patients with systemic lupus erythematosus

OBJECTIVE

This was an open-labeled, prospective, control study to determine the efficacy of methotrexate (MTX) for improving serological abnormalities in patients with systemic lupus erythematosus (SLE).

METHODS

Thirty patients with a low serum complement and/or high anti-double-stranded DNA (dsDNA) antibody levels during a prednisolone taper received MTX orally at a dose of 7.5 mg/week over 12-18 months (MTX group). Eighteen SLE patients were selected as controls (control group). At the time of entrance into the study, all patients were receiving <15 mg/day of prednisolone. The C3, C4, and immunoglobulin (Ig)G, IgA, and IgM levels were measured using a turbidimetric immunoassay. The anti-dsDNA antibody level was measured using the Farr assay.

RESULTS

Significant increases in C3 and C4 levels and significant decreases in anti-dsDNA antibody, IgG, IgA, and IgM levels from baseline were observed for 3-18 months after the trial in the MTX group but not in the control group. At the end of the study, C3 and/or C4 levels in 96.7% of the MTX patients and 33.3% of the control patients were normalized or elevated (p = 0.0001), and anti-dsDNA antibody levels were normalized or lowered in 24 of the 26 MTX patients (92.3%) and in 50.0% of the control patients (p = 0.0022). In addition, a significant reduction in SLE Disease Activity Index (SLEDAI) score and a prednisolone-sparing effect were observed for the MTX group but not the control group. A significant increase in mean corpuscular volume of red blood cells, which is indicative of an anti-folic-acid metabolic disorder induced by MTX, was observed only for patients in the MTX group. Five patients (16.7%) discontinued MTX treatment because of disease flare, and another three (10.0%) discontinued due to treatment side effects.

CONCLUSION

MTX appears to be effective for improving serological abnormalities frequently observed before disease flares in SLE patients on a prednisolone taper.

Antinucleosome antibodies as a potential biomarker for the evaluation of renal pathological activity in patients with proliferative lupus nephritis

The objective of this study is to evaluate the correlation between antinucleosome antibodies and renal pathological activity in patients with proliferative lupus nephritis (LN). We evaluated 36 patients with proliferative LN, 14 non-renal lupus patients and 10 healthy volunteers. Lupus activity was assessed using the British Isles Lupus Assessment Group 2004 (BILAG 2004) index, serum anti-double stranded DNA (anti-dsDNA) levels, serum complement levels and daily urinary protein levels. All 36 lupus nephritis patients received renal biopsy. Antinucleosome antibodies were detected by enzyme-linked immunosorbent assay (ELISA). Our results showed that levels of serum antinucleosome antibodies were significantly higher in LN patients (median 90.35 units/ml, interquartile range [IQR] 37.38–135.23) than in non-renal SLE patients (median 5.45 units/ml, IQR 2.6–28.93, p <0.05) and in healthy volunteers (median 3.35 units/ml, IQR 2.95–5.23, p <0.001). Serum levels of antinucleosome antibodies were positively correlated with BILAG index (Spearman’s r = 0.645, p <0.001) and serum anti-dsDNA antibody levels ( rs = 0.644, p <0.01), while serum levels of antinucleosome antibodies were negatively correlated with serum levels of C3 ( rs = -0.400, p <0.01) and C4 ( rs = -0.300, p <0.05). Serum levels of antinucleosome antibodies were positively correlated with the histological activity index of LN ( rs = 0.368, p <0.05). However, there was no significant correlation between serum levels of antinucleosome antibodies and the histological chronicity index. In conclusion, the serum level of antinucleosome antibodies is a potential biomarker for early recognition of renal involvement and evaluation of disease activity in SLE. Our preliminary results suggested that serum levels of antinucleosome antibodies might be a potential biomarker in evaluating pathological activity of LN.

The use of laboratory methods in differential diagnosis and treatment of SLE and antiphospholipid syndrome

The detection of autoantibodies has become an important component in the diagnosis and management of systemic lupus erythematosus (SLE) and antiphospholipid syndrome. Their importance lies in the fact that they are not only markers of the disease and used as part of a diagnostic panel, but many of them also show correlation with disease activity. All antibody testing should be interpreted in the context of the clinical features. The antinuclear antibodies test is an effective screening assay in patients with clinical features of SLE. The combination of antinuclear antibodies test, dsDNA and ENA (Ro, La, Sm, RNP) antibodies help to establish the diagnosis of most patients with SLE. New antibodies, such as antinucleosomes and anti-C1q, appear to be useful for SLE diagnosis, monitoring disease activity and predicting renal flares, particularly in dsDNA-negative patients. Anticardiolipin antibodies and lupus anticoagulant are the tests most commonly used in the diagnosis of antiphospholipid syndrome. However, the use of anti-beta(2)-glycoprotein I as a routine diagnostic test remains controversial.

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

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

Diagnosing systemic lupus erythematosus: new-generation immunoassays for measurement of anti-dsDNA antibodies are an effective alternative to the Farr technique and the Crithidia luciliae immunofluorescence test

The aim of this study was to evaluate the diagnostic performance of four new enzyme immunoassays (EIAs) for anti-double-stranded-DNA (anti-dsDNA) antibodies, in comparison with the Farr assay and the Crithidia luciliae immunofluorescence test (CLIFT). To this purpose, sera from four patient groups were collected: 52 sera from patients with systemic lupus erythematosus (SLE); 28 from patients with other connective tissue diseases (CTD); 36 from patients with hepatitis C virus (HCV) infection; and 24 from those with acute viral infection. All sera were tested for anti-dsDNA antibodies by four EIA methods using a different antigenic DNA source [synthetic oligonucleotide (Method A), circular plasmid (Method B), recombinant (Method C), and purified extracted (Method D)], and by CLIFT and Farr assays. The diagnostic sensitivity of the assays was as follows: 84.6% (Method A), 73% (B), 82.7% (C), 84.6% (D), 55.8% (CLIFT), and 78.8% (Farr). Specificity was 82.9% (A), 97.7% (B), 96.5% (C), 94.3% (D), 96.5% (CLIFT), and 90.9% (Farr). From these data, we can conclude that the new-generation EIA methods evaluated in this study have higher sensitivity than the CLIFT and Farr assays and, with the exception of Method A, have specificity similar to the CLIFT and slightly higher than the Farr assay. These findings suggest that EIA tests may replace CLIFT as a screening test and the Farr assay as a specific test, for anti-dsDNA antibody detection.

Abetimus sodium for renal flare in systemic lupus erythematosus: results of a randomized, controlled phase III trial

OBJECTIVE

To investigate whether treatment with abetimus delays renal flare in patients with lupus nephritis. Secondary objectives included evaluation of the effect of abetimus on C3 levels, anti-double-stranded DNA (anti-dsDNA) antibody levels, use of high-dose corticosteroids and/or cyclophosphamide, and major systemic lupus erythematosus (SLE) flare.

METHODS

We conducted a randomized, placebo-controlled study of treatment with abetimus at 100 mg/week for up to 22 months in SLE patients. Three hundred seventeen patients with a history of renal flare and anti-dsDNA levels >15 IU/ml were randomized to a treatment group (158 abetimus, 159 placebo); 298 (94%) were enrolled in the intent-to-treat (ITT) population (145 abetimus, 153 placebo), based on the presence of high-affinity antibodies for the oligonucleotide epitope of abetimus at baseline screening.

RESULTS

Abetimus did not significantly prolong time to renal flare, time to initiation of high-dose corticosteroid and/or cyclophosphamide treatment, or time to major SLE flare. However, there were 25% fewer renal flares in the abetimus group compared with the placebo group (17 of 145 abetimus-treated patients [12%] versus 24 of 153 placebo-treated patients [16%]). Abetimus treatment decreased anti-dsDNA antibody levels (P < 0.0001), and reductions in anti-dsDNA levels were associated with increases in C3 levels (P < 0.0001). More patients in the abetimus group experienced > or =50% reductions in proteinuria at 1 year, compared with the placebo group (nominal P = 0.047). Trends toward reduced rates of renal flare and major SLE flare were noted in patients treated with abetimus who had impaired renal function at baseline. Treatment with abetimus for up to 22 months was well tolerated.

CONCLUSION

Abetimus at 100 mg/week significantly reduced anti-dsDNA antibody levels but did not significantly prolong time to renal flare when compared with placebo. Multiple positive trends in renal end points were observed in the abetimus treatment group.

A prospective study of anti-chromatin and anti-C1q autoantibodies in patients with proliferative lupus nephritis treated with cyclophosphamide pulses or azathioprine/methylprednisolone

OBJECTIVE

To study the prevalence and course of anti-chromatin (anti-nucleosome, anti-double-stranded (ds) DNA and anti-histone) and anti-C1q autoantibodies in patients with proliferative lupus nephritis (LN), treated in a randomised controlled trial with either cyclophosphamide or azathioprine plus methylprednisolone.

METHODS

Autoantibody levels were measured and analysed in 52 patients with proliferative LN, during their first year of treatment. Levels in both treatment arms were compared and associations with clinical, serological and outcome parameters were studied.

RESULTS

At study entry, prevalences for anti-nucleosome, anti-dsDNA, anti-histone and anti-C1q autoantibodies were 81%, 96%, 23% and 65%, respectively. Anti-chromatin autoantibodies correlated with each other, but not with anti-C1q levels. If patients were divided for their autoantibody titre at the start of treatment above or below the median, the only significant differences were higher SLE disease activity index with higher anti-nucleosome, and higher creatinine with higher anti-C1q autoantibodies. During the first year, a comparable rapid decline in the levels of anti-nucleosome, anti-dsDNA and anti-C1q autoantibodies was seen in both treatment arms. Anti-histone autoantibody levels were low and did not change. Renal flares were not preceded by rises in autoantibody titres.

CONCLUSIONS

These results indicate that measurement of anti-chromatin and anti-C1q autoantibodies is useful for diagnosing LN, but not for monitoring disease course.

Quantitation of autoantibodies in systemic autoimmune diseases: clinically useful?

Serial assessment of levels of autoantibodies has been proposed as being clinically useful in certain systemic autoimmune diseases. In particular, attention has been given to anti-dsDNA antibodies in systemic lupus erythematosus (SLE) and ANCA in the ANCA-associated vasculitides (AAV). Much controversy exists, however, concerning the value of serial testing in these diseases. We here review the various tests available for quantitation of anti-dsDNA and ANCA, and their capacity to detect changes in autoantibody levels that are associated with changes in clinical disease activity of the respective diseases. It is concluded that changes in anti-dsDNA as measured by the Farr assay and changes in ANCA as assessed by ELISA have predictive value for the occurrence of disease relapses, although this relationship is far from absolute. Consequently, treatment based on changes in levels of the respective autoantibodies only seems at present not justified, in view of the toxicity of currently available immunosuppressive regimens.

Abetimus sodium: a new therapy for delaying the time to, and reducing the incidence of, renal flare and/or major systemic lupus erythematosus flares in patients with systemic lupus erythematosus who have a history of renal disease

The safety and efficacy of abetimus sodium (abetimus) has been evaluated in 13 controlled and uncontrolled clinical trials involving > 800 patients or subjects. The two pivotal trials enrolled a total of 547 patients with systemic lupus erythematosus (SLE) who had a history of lupus nephritis. Evidence of clinical effectiveness of abetimus comes from analyses of data from patients with SLE and high-affinity antibodies to the DNA epitope of abetimus at baseline; a retrospective subgroup in the pivotal Phase II/III LJP-394-90-05 trial (90-05 trial) and the intent-to-treat population in the Phase III LJP-394-90-09 trial (90-09 trial). These studies enrolled SLE patients who had experienced prior renal manifestations of their disease and had elevated anti-dsDNA antibodies at baseline by Farr assay. Both were long-term studies, with a mean duration of treatment participation of 371 days in 90-05 and 310 days in 90-09 for the population of patients with high-affinity antibodies at baseline. The 90-05 and 90-09 studies, as well as all other clinical studies of abetimus, consistently showed that treatment with abetimus resulted in durable and persistent reductions in anti-dsDNA antibodies in SLE patients. Treatment with abetimus was associated with statistically significant decreases in anti-dsDNA antibody levels from baseline compared with placebo in both the 90-09 and 90-05 trials. Positive trends were noted for the incidence of renal flares and major SLE flares in patients treated with abetimus. Abetimus appeared to be well tolerated for treatment periods of < or = 22 months.

Inhibition of lupus disease by anti-double-stranded DNA antibodies of the IgM isotype in the (NZB x NZW)F1 mouse

OBJECTIVE

In systemic lupus erythematosus (SLE), immune complexes (ICs) containing pathogenic IgG anti-double-stranded DNA (anti-dsDNA) autoantibodies are deposited in renal capillaries and initiate glomerulonephritis (GN) by the activation of complement and effector cells. In contrast, it has been demonstrated that the presence of IgM anti-dsDNA antibodies correlates negatively with the development of GN in SLE. The aim of this study was to determine whether anti-dsDNA antibodies of the IgM isotype protect against IC-mediated organ damage in SLE.

METHODS

Lupus-prone (NZB x NZW)F(1) mice (females) were treated with murine monoclonal IgM anti-dsDNA antibodies. Treatment was delivered by subcutaneous injection at a dosage of 100 mug/week starting at 16 weeks of age (prophylactic) or at 24 weeks of age (therapeutic).

RESULTS

Mice treated with IgM anti-dsDNA exhibited a delayed onset of proteinuria and a reduced degree of renal pathology, which resulted in significantly improved survival as compared with control mice. Serum concentrations of IgG anti-dsDNA antibodies were not significantly modified. However, glomerular deposition of ICs was markedly reduced in both treatment protocol groups. In contrast, higher amounts of IgG and IgM and increased expression of Fcgamma receptor were demonstrated in liver sections from the treated mice compared with the untreated mice, suggesting an enhanced clearance of soluble ICs from phagocytic cells of the reticuloendothelial system.

CONCLUSION

These data demonstrate the efficacy of IgM anti-dsDNA treatment in inhibiting the pathologic changes of lupus in (NZB x NZW)F(1) mice. Lower glomerular IC deposition is associated with a reduced inflammatory response and impaired organ damage. The reduced frequency of GN in SLE patients who have IgM anti-dsDNA antibodies may therefore reflect a disease-modifying effect of this class of autoantibodies that has potential therapeutic implications. Our findings should encourage the development of new therapeutic modalities using IgM anti-dsDNA antibodies in humans with SLE.

Relationship between anti-double-stranded DNA antibodies and exacerbation of renal disease in patients with systemic lupus erythematosus

OBJECTIVE

To examine the relationship between changes in anti-double-stranded DNA (anti-dsDNA) antibody levels and the risk of renal flare in patients with systemic lupus erythematosus (SLE), using data from 2 randomized, controlled trials.

METHODS

Analyses were based on 487 patients with SLE and a history of lupus nephritis who had an anti-dsDNA antibody titer >/=15 IU/ml at baseline, as measured by Farr assay. Results are presented for the combined population of patients, the placebo arms, and the drug treatment arms in which a dsDNA-based bioconjugate (abetimus sodium; LJP 394) was used.

RESULTS

Changes in anti-dsDNA antibody levels were inversely correlated with changes in the C3 level (P < 0.0001 in both trials). Cox proportional hazards regression models showed that changes in anti-dsDNA antibody levels correlated with the risk of renal flare. The models predicted that a point estimate of a 50% reduction in anti-dsDNA antibody levels is associated with a 52% reduction (95% confidence interval [95% CI] 26-68%, nominal P = 0.0007) and a 53% reduction (95% CI 33-69%, nominal P < 0.0001) in the risk of renal flare in the 2 trials, respectively. In the 2 trials, the incidence of renal flare was lower in patients with sustained reductions in anti-dsDNA antibodies (3.0% and 4.1%, respectively) than in patients with stable or increasing antibody levels (21.3% and 20.3%, respectively).

CONCLUSION

Changes in anti-dsDNA antibody levels were directly correlated with the risk of renal flare and inversely correlated with changes in the C3 level. Reducing anti-dsDNA antibody levels may represent a therapeutic objective in SLE patients with lupus nephritis, because it is associated with a reduced risk of renal flare.

Clinical evaluation of cobas core anti-dsDNA EIA quant

The measurement of antibodies to double-stranded DNA (anti-dsDNA) is a useful tool for the diagnosis and monitoring of patients with connective tissue diseases, particularly systemic lupus erythematosus (SLE). The aim of the present study was to compare a new enzyme-linked immunosorbent assay (ELISA) for the measurement of anti-dsDNA antibodies, which uses purified double-stranded plasmid DNA as the antigen (anti-dsDNA EIA Quant; Roche Diagnostics, Mannheim, Germany), with an established ELISA. The clinical usefulness of this new ELISA was also assessed. We measured anti-dsDNA antibodies in 398 serum samples that were divided into four groups: 1). routine samples sent to our laboratory for an antinuclear antibody (ANA) test (n=229), 2). samples from blood donors (n=74), 3). samples from patients with SLE (n=48), and 4) samples from patients with other autoimmune diseases (n=47). The methods used were the Cobas Core Anti-dsDNA EIA Quant (Roche Diagnostics, Mannheim, Germany) and the Anti-dsDNA test (Gull Diagnostics, Bois d'Arcy, France). We obtained a kappa index and Spearman correlation coefficient in the comparative study, and sensitivity, specificity, predictive values, and likelihood ratios in the clinical study. The results obtained show a good agreement between the two methods in both the qualitative results (kappa=0.91) and the quantitative data (r=0.854). The best accuracy, predictive values, likelihood ratios, and correlation with active disease were obtained with the Roche anti-dsDNA assay.

Gene immunization may induce secondary antibodies reacting with DNA

The fear of autoimmunity in DNA-vaccine recipients initiated screening for anti-DNA antibodies in rabbits immunized with genes of viral nucleic acid-binding and adapter proteins. Of 11 DNA/protein-immunized rabbits, seven had developed secondary antibodies against DNA detected at weeks 11-50 from the on-start of immunization. Two rabbits immunized with HIV-1 reverse transcriptase gene developed transient anti-double-stranded DNA antibodies of high avidity that recognized DNA in the kinetoplasts of Crithidia luciliae. Others developed antibodies reacting with DNA in ELISA and targeting nuclear-associated antigens in the immunofluoresence test. No anti-DNA antibodies were detected at these time-points in any of the controls (P=0.036). Induction of anti-DNA antibodies by epitope spreading from protein domains involved in nucleic acid-binding versus maturation of anti-protein antibodies to dual protein-DNA specificity is discussed. (126 words).

Anti-dsDNA antibodies and disease classification in antinuclear antibody positive patients: the role of analytical diversity

BACKGROUND

The presence of "anti-DNA antibodies in abnormal titres" is a well established criterion for SLE classification, but there is no agreement on the performance of this test.

OBJECTIVE

To study the correlation between clinical findings and five different solid and solution phase anti-DNA antibody assays.

METHODS

158 consecutively collected ANA positive sera were studied in a double blind fashion. Anti-DNA antibodies were determined by different solid phase assays (ssDNA-, dsDNA- specific ELISA, EliA anti-dsDNA assay, Crithidia luciliae assay), and by an experimental solution phase anti-DNA assay using biotinylated pUC18 plasmid, human, calf thymus, and E coli DNA. Antibody affinity was determined by surface plasmon resonance. Clinical data were obtained independently of the laboratory analyses and later related to the anti-dsDNA findings.

RESULTS

Anti-dsDNA antibodies were most frequently detected by ELISA, but were not specific for SLE as they were present in up to 30% of other disease groups. Those detected by the Crithidia luciliae assay were predictive for SLE, while antibodies binding in solution phase ELISA using the pUC18 correlated strongly with the Crithidia luciliae assay. Surface plasmon resonance analysis showed that antibody binding to pUC18 was not due to higher relative affinity for dsDNA in general, but apparently to specificity for that plasmid DNA. Serum samples from three patients with lupus nephritis were positive in both pUC18 solution phase and Crithidia luciliae assays.

CONCLUSIONS

Assay principle selection is decisive for the detection of clinically significant anti-DNA antibodies. Revision of the anti-DNA antibody criterion in the SLE classification may be needed.

Anti-DNA antibodies--overview of assays and clinical correlations

Many authors have studied the links between levels of anti-dsDNA antibodies and disease activity in patients with SLE. Interpretation of these studies must take into account the facts that there are a range of possible assays for anti-dsDNA and a number of indices available for assessing disease activity. A recent study compared levels of various autoantibodies with organ specific disease activity assessed during the British Isles Lupus Assessment Group (BILAG) index. Anti-dsDNA and anti-heparan sulphate levels were more likely to be raised in patients with renal than non-renal disease. Some anti-DNA antibodies are actually anti-nucleosome antibodies, which lose DNA reactivity when purified under dissociating conditions. Patients with SLE have significantly increased levels of nucleosomes in their sera compared with healthy controls. In patients with SLE, reduced clearance of nucleosomes released from apoptotic cells may induce the formation of anti-nucleosome antibodies.

Use of a new fluorescence immunoassay to detect anti-dsDNA antibodies is more correlated with disease activity and complement than the ELISA method in SLE patients

To determine whether the serum levels of anti-double strand DNA (anti-dsDNA) autoantibodies detected using a newly developed fluorescence immunoassay (FIA) in patients with systemic lupus erythematosus (SLE) correlated more with clinical parameters, such as SLE disease activity index (SLEDAI), complement and the occurrence of nephritis when compared with traditional enzyme-linked immunosorbent assay (ELISA), we prospectively collected 124 serum samples from 31 patients who had juvenile-onset SLE and were regularly monitored every 2 months at our outpatient clinic. At every visit, clinical manifestations and laboratory parameters were assessed and the SLEDAI was determined. Correlation analyses between the two different measurements of anti-dsDNA antibodies and SLEDAI, serum complement levels and the occurrence of nephritis were performed. The results showed that anti-dsDNA autoantibodies detected using both ELISA and FIA significantly correlated with SLEDAI, and significantly and inversely correlated with the serum levels of C3 and C4. FIA had significantly higher correlation with SLEDAI and C4 than did ELISA. The mean values of anti-dsDNA antibodies detected using FIA in patients with nephritis were significantly higher than in those without nephritis. In contrast, the values of anti-dsDNA antibodies detected using ELISA did not show significant differences between these two groups. We conclude that FIA had better correlation with SLEDAI, C4 and the occurrence of nephritis, and comparable correlations with C3 that were similar to the results found using ELISA. Thus, it is worthwhile developing the FIA method for clinical evaluation of disease activity in SLE patients.

A comparison between the Farr radioimmunoassay and a new automated fluorescence immunoassay for the detection of antibodies against double stranded DNA in serum

OBJECTIVE

To compare test characteristics of the Farr radioimmunoassay and an automated fluorescence immunoassay (ELIA dsDNA test) for the diagnosis of systemic lupus erythematosus (SLE).

METHODS

A cross sectional study comprising 440 samples from 440 patients, sent to the laboratory over a three month period for anti-dsDNA testing. Chart review was performed, blinded for test results, to count for each patient the number of American College of Rheumatology criteria for the classification of SLE that were fulfilled. At least four criteria were met by 248 (56%) patients (SLE), one to three criteria by 77 (18%) (lupus-like disease, LLD), and no criterion by 115 (26%) (non-SLE/non-LLD). Results from serum samples from the non-SLE/non-LLD and SLE groups were used to calculate receiver operating characteristic curves.

RESULTS

For the Farr assay, specificities of 95% and 99% corresponded to sensitivities of 72% and 56% respectively. For the ELIA dsDNA test these levels of specificity corresponded to sensitivities of 44% and 17% respectively.

CONCLUSIONS

The Farr radioimmunoassay is superior to the ELIA dsDNA test for identifying patients with SLE.

Clinical evaluation of a new automated anti-dsDNA fluorescent immunoassay

The measurement of anti-double-stranded DNA (anti-dsDNA) antibodies is a useful tool for the diagnosis and the follow-up of systemic lupus erythematosus (SLE). Anti-dsDNA antibodies are involved in the pathogenesis of lupus nephritis and they are, specially the high-avidity antibodies, the most specific antibodies associated with SLE nephritis and active SLE. The aim of the present study was to assess the clinical utility of an enzyme-linked immunosorbent assay (EUSA) that utilizes a circular double-stranded plasmid DNA as a nucleic acid source, adapted to an automated fluorescence immunoassay (EliA dsDNA, Pharmacia, Freiburg, Germany). Also, we compared this method with other immunoassays used in clinical laboratories. We have measured anti-dsDNA antibodies in the serum of 179 patients with a positive result for antinuclear antibodies (ANA). Seventy six sera were from SLE patients (14 men and 62 women), and the other 103 sera (from 20 men and 83 women) constituted the control group. This latter group includes nine Sjogren's syndrome patients, six patients with rheumatoid arthritis and 88 with various other diseases, including connective tissue diseases (n=34), hepatopathies (n= 17; 11 primary biliary cirrhosis and 6 autoimmune hepatitis), and 37 patients with nonautoimmune diseases (viral hepatitis, renal disease, diabetes, exanthema and hypertension). Methods used were "EliA dsDNA" (Pharmacia, Germany), "Varelisa dsDNA" (Pharmacia, Germany), Farr (Amersham, UK) and Chritidia luciliae immunofluorescence test (Vitro-Immun, Germany). We assessed sensitivity, specificity, positive predictive value and negative predictive value in the clinical study, and kappa index and scatter plots in the comparative study. The results show a low concordance between methods (kappa < 0.6). The evaluated EliA method shows a very good specificity for SLE (93.2%) and a good sensitivity for active SLE (70.8%).

Development of anti-dsDNA autoantibodies prior to clinical diagnosis of systemic lupus erythematosus

Anti-double stranded (dsDNA) antibodies are of considerable diagnostic value and are thought to be involved in the pathogenesis of systemic lupus erythematosus (SLE). Fluctuations in anti-dsDNA antibody levels are also used as markers for disease activity and exacerbations. In this study we sought to evaluate the anti-dsDNA antibody level in serum samples collected before the onset of SLE diagnosis. A total of 130 SLE patients were identified with stored serum samples available prior to diagnosis within the US Department of Defense serum repository. All 633 sera available from these patients were screened for anti-dsDNA antibodies using an enzyme linked immunosorbant assay (ELISA). Within this cohort 55% of cases had detectable anti-dsDNA antibodies prior to SLE diagnosis. The onset of anti-dsDNA antibodies ranged from 9.3 years before to within the same month as diagnosis (with a mean onset 2.7 years before diagnosis). In order to assess for fluctuations in anti-dsDNA levels relative to diagnosis, cases were selected with at least two positive samples, one within 6 months and a second greater than 6 months prior to diagnosis (n = 26). Seven of these cases also had samples available shortly after diagnosis (< or = 6 months) for comparison. Fifty-eight percent of the 26 cases developed a significant rise in anti-dsDNA antibody levels within 6 months of diagnosis. A significant decline in anti-dsDNA levels ensued after diagnosis (and following treatment with corticosteroids) in all seven cases with samples available. Patients with a significant rise in anti-dsDNA antibodies at diagnosis were more likely to have renal disease than those who did not (66.7% compared to 27.3%, chi2 =3.94, P<0.05). These data suggest that anti-dsDNA antibodies are present in SLE patient sera much earlier than previously suspected. In addition, the data are consistent with increases in anti-dsDNA levels contributing to the onset of clinical illness in some patients with SLE.

Histone-containing immune complexes are to a large extent responsible for anti-dsDNA reactivity in the Farr assay of active SLE patients

Increased titres of anti-dsDNA antibodies, especially if of high avidity, are associated with renal exacerbations in patients with systemic lupus erythematosus (SLE). One of the most reliable assays to measure anti-dsDNA antibodies, the Farr assay, is believed to detect preferentially high avidity antibodies. Purified non-complexed monoclonal antibodies (mAbs) against nucleosomes, obtained from mice with SLE, are not reactive in the Farr assay, but can become so once complexed to nucleosomes. These Farr-positive, nucleosome containing, immune complexes were also able to bind in vivo to the glomerular basement membrane (GBM), predominantly via heparan sulphate (HS). To evaluate whether in SLE patients the same kind of immune complexes are responsible for Farr reactivity, IgG from serum or plasma was isolated under dissociating and physiological conditions. We observed that after purification under dissociating conditions, Farr reactivity was significantly decreased (P<0.0001) in contrast to reactivity with histones and two 'control' antigens: Epstein Barr Virus (EBV) and Ro/SS-A. Reactivity with nucleosomes also decreased after purification, although to a lesser extent. Plasma purified under physiological conditions showed no decrease in Farr reactivity. The importance of histones for the generation of immune complexes is supported by the two following observations. Firstly, the presence of histones could be demonstrated in serum and plasma of SLE patients but not in serum of healthy controls or in IgG preparations purified under dissociating conditions. Secondly, Farr reactivity of purified IgG preparations could be restored by addition of purified histones. From these studies we conclude that histones containing immune complexes are responsible for a large part of the Farr reactivity in active SLE, and are therefore indirectly implicated in the pathogenesis of lupus nephritis.

Variability between methods to determine ANA, anti-dsDNA and anti-ENA autoantibodies: a collaborative study with the biomedical industry

This study was performed by the Italian Society of Laboratory Medicine (SIMeL) in order to establish the variability between the different analytical systems currently used in clinical laboratories for the detection of autoantibodies diagnostic of systemic autoimmune disease. Sixteen industrial, and two university laboratories participated in this study which entailed the determination of anti-nuclear (ANA), anti-dsDNA and anti-ENA antibodies in 11 sera from patients with clinically diagnosed systemic rheumatic disease, using reagents produced by these companies and different methodologies (indirect immunofluorescence, immunoenzymatic assay, counterimmunolectrophoresis, immuno and western blotting). We found 93.5% agreement between the methods used for the detection of ANA, 85.2% for anti-dsDNA antibodies, and 86.9% for anti-ENA antibodies. Among the anti-ENA antibodies, regardless of the method used, detection percentages were excellent for anti-RNP and anti-SSB/La (100%), good for anti-SSA/Ro (93%), but unacceptable for the anti-Jo-1 (67%), anti-Scl70 and anti-Sm (47%) antibodies. This further stresses the need for rigorous standardisation of commercial reagents and analytical procedures, as well as the introduction of external quality assessment (EQA) programs, and a complete definition of operative protocols adjusted to the sensitivity and specificity of the various methods.

Detection of restricted junctional diversity of peripheral T cells in SLE patients by spectratyping

Analysis of somatic mutations revealed that anti-double-stranded DNA (dsDNA) autoantibodies from patients with systemic lupus erythematosus (SLE) share features of a T cell dependent, antigen driven immune response. Therefore we analysed the length diversity of the complementarity determining region 3 (CDR3) of T cell receptor (TCR) by high resolution gel electrophoresis of 16 V beta family specific RT PCR products (spectratyping). To enable statistical analysis we developed a quantitative scoring method for the histograms. We investigated 16 V beta gene families in peripheral T cells of SLE patients (n = 9) with active (n = 5) and inactive (n = 4) disease as well as normal healthy blood donors (NHD; n = 9). Analysis of TCR V beta spectratypes (active SLE, n = 59; inactive SLE, n = 51 and NHD n = 97) revealed statistically significant differences of CDR3 length distribution between SLE patients and NHD (P < 0.0001 (active SLE/NHD) and P = 0.0034 (inactive SLE/NHD). These results suggest that spectratyping is able to detect clonal activation of peripheral T cells which correlates to disease activity in SLE patients. We conclude that peripheral T cells from SLE patients display features of a secondary antigen driven immune response.

Laboratory studies in breast implant patients: ANA positivity, gammaglobulin levels, and other autoantibodies

Silicone polymers when used in augmentation prosthesis in breast surgery have been associated in the medical literature with various systemic clinical manifestations and abnormal laboratory testing suggestive of an atypical autoimmune disease. The most frequently cited abnormal test result is the antinuclear antibody. The literature regarding this test is reviewed in general, and then specific previous studies analyzed. The present study then compares the rate of positive antinuclear antibody tests in a case series of 3380 breast implant recipients with historical normal controls, and finds a six-fold increase in relative risk of a positive test. Analysis of the data show that this increased tendency is at least partially a function of duration of implant exposure to a significant degree (p < 0.001), and the same data shows it is not patient age related. Possible explanations of this phenomenon are discussed, including animal studies suggesting that silicone serves as an adjuvant, and therefore might have an effect on immune tolerance in the subject population.

Serological markers of disease activity in systemic lupus erythematosus

When measured serially by Farr assay at a frequency of approximately once a month, changes in levels of anti-dsDNA appear to be a good predictor of clinical disease activity. Although the role of antibodies to the RNA component of snRNP awaits further studies, measurement of anti-UsnRNP antibody levels seems to be of limited value in monitoring lupus patients in clinical practice. The same holds for antibodies to SSA (Ro) and anti-histone antibodies. More recently described antibodies to C1q are probably useful in the follow-up of SLE patients suspected of proliferative renal involvement. The best alternative to measuring levels of the antibodies mentioned before is probably serial analysis of activation of the complement cascade. Levels of complement factors like C3, C4 and, functionally, CH50 remain a useful parameter for monitoring disease activity in SLE, although fluctuations in anti-dsDNA as measured by Farr assay seem superior with respect to sensitivity and specificity for an ensuing relapse. Despite the problems in sampling, measuring levels of activated split products of complement factors like C3a, C3d or C5a may prove to be a valuable tool in the follow-up of lupus patients. The involvement of the endothelial surface is illustrated by rising sVCAM-1 levels prior to relapses in SLE. Although one could expect that subsequent inflammation should be reflected by increased levels of inflammatory molecules like CRP and IL-6, the use of these molecules as predictors of lupus activity seems limited. Interferon-alpha as a direct reflector of the effector phase seems, however, rather promising in this respect and awaits longitudinal studies to analyse the possible relation with clinical disease activity and other serological parameters.

Canine systemic lupus erythematosus: new insights and their implications

It is generally considered that the clinical manifestations of human and canine systemic lupus erythematosus (SLE) are similar in many respects. However, there are differences in serological markers of SLE between the two species, which has led to much discussion on which immunopathological criteria might be appropriate in the diagnosis of the canine disorder. Further studies on canine SLE will need to address these issues, so that definitive diagnostic indices may be employed. Areas which require to be re-assessed, in particular, include the applicability of assays for antibodies to double-stranded DNA--a hallmark of human SLE, a re-evaluation of the anaemia associated with canine SLE and an index of the clinical activity of the disease process.

The clinical significance of measuring different anti-dsDNA antibodies by using the Farr assay, an enzyme immunoassay and a Crithidia luciliae immunofluorescence test

Anti-double-stranded DNA (dsDNA) antibodies are highly specific for the diagnosis of systemic lupus erythematosus (SLE) but are heterogeneous in respect to, for example, avidity, class and cross-reactivity. Sera from 2061 patients were measured by three methods: an enzyme-linked immunosorbent assay (ELISA), an indirect immunofluorescence test with Crithidia luciliae as substrate (CLIF), and the Farr assay, a radioimmunological method based on the ammonium sulfate precipitation of immune complexes. The different anti-dsDNA antibody determinations were evaluated by analysis of patient records. The reason for a reactive Farr assay in 14 patients was predominantly the measurement of antibodies of the IgM class, which are not detected by the ELISA. The detection of additional antibodies to dsDNA of the IgA class, to single-stranded DNA or to histones plays a minor role. In comparison with the Farr assay, we found more positive results with the ELISA, which additionally detects anti-dsDNA antibodies of low avidity. The ELISA might also yield positive values in conditions such as chronic liver diseases, various infections and connective tissue diseases other than SLE. Avoiding the disadvantages of radioactivity, the ELISA is well suited as a screening test for dsDNA antibodies. However, positive results should be confirmed by the CLIF test or preferably by the Farr assay, thus combining sensitivity with specificity.