Evidence-based guidelines for the use of immunologic tests: antinuclear antibody testing

Italian multicentre study for application of a diagnostic algorithm in autoantibody testing for autoimmune rheumatic disease: conclusive results

AIM

The presence of specific auto-antibodies in serum (i.e., antinuclear antibodies or ANA, anti-extractable nuclear antigens or anti-ENA, and anti-double stranded DNA or anti-dsDNA ) is one of the major criteria in the diagnostics of Autoimmune Rheumatic Disease. As such, the request for these tests has grown exponentially in laboratory practice. The aim of this study is to describe the implementation of a joint laboratory-clinics guideline for reducing clinically inappropriate requests for autoantibody testing in a broad geographic area (Parma, Modena, Piacenza, Reggio-Emilia) for the diagnosis of Autoimmune Rheumatic Disease.

METHODS

This study, supported by a Regional grant for innovative research projects started in January 2008, is an observational research aimed at comparing the number of ANA, anti-dsDNA and anti-ENA testing as well as the percentage of positive test results before and after implementation of the diagnostic algorithm in hospitalized patients. A multidisciplinary team consisting of clinical immunologist and laboratory scientists was established, with the aim of collecting and analysing diagnostic criteria, clinical needs, laboratory report formats, analytical procedures, as well as the number of tests performed. The laboratory results and the clinical protocol were both validated by data emerging from the clinical follow-up studies.

RESULTS

A joint guideline for auto-antibody testing, placing ANA test at the first level, has been developed and implemented since January 2009. The results for the period January-June 2009 (12,738 tests) were compared with those of the same period in 2008 (13,067 tests). A significant reduction in the number of anti-dsDNA (-26%) and anti-ENA (-15%) was observed. The percentage of second-level tests positivity after implementation of the diagnostic protocol had also consistently increased for both ENA (13% vs 17%) and dsDNA (9% vs 11%).

DISCUSSION

The development and implementation of algorithms for the diagnostics of Autoimmune Rheumatic Disease in hospitalized patients was associated with a reduction in the number of second-level tests, but also with an increased diagnostic specificity. This outcome attests that close collaboration and audit between clinicians, laboratory specialists and healthcare services is effective to develop efficient diagnostic algorithms for both hospitalized patients and outpatients.

Autoantibody detection with indirect immunofluorescence on HEp-2 cells: starting serum dilutions for systemic rheumatic diseases

Antinuclear antibodies (ANA) are determined, among other reasons, to identify samples which need a second test to detect the associated specificities. Our aim was to evaluate the clinical and economic impact generated by using an initial dilution for ANA of 1:160. We analyzed all samples for which ANA, anti-ENA and anti-dsDNA were requested over a 1-year period. ANA were detected by indirect immunofluorescence. Anti-ENA were analyzed with a combination of techniques. Anti-dsDNA were detected by radioimmunoassay. Cost analysis was performed by calculating the difference between two cut-offs (ANA 1:40 and 1:160). A total of 13,233 samples were processed for ANA, of which 59.9% were positive with the 1:40 cut-off and 39.2% with the 1:160 cut-off. At ANA titer 1:40, 0.2% of the samples were anti-ENA-positive and 2.2% were anti-dsDNA positive. Only ANA dilutions of 1:160 and higher showed significantly increased positive predictive value for anti-ENA (1.5 versus 0.2, p=0.029) and anti-dsDNA (8.3 versus 2.2, p<0.001) compared to the 1:40 titer. With the 1:160 cut-off, 16.6% fewer ANA tests, 41.8% fewer anti-ENA determinations and 36.4% fewer anti-dsDNA tests would have been needed. The average saving was 0.87 cost-units per sample (1 unit=2.06euro). We conclude that setting the starting dilution for ANA at 1:160 avoids unnecessary studies, increases the positive predictive values of ANA for anti-ENA and anti-dsDNA, and generates clinical and economic benefits.

Thrombotic microangiopathic hemolytic anemia with reduction of ADAMTS13 activity: initial manifestation of childhood-onset systemic lupus erythematosus

Severe manifestations of systemic lupus erythematosus (SLE), antiphospholipid syndrome (APS), and thrombotic thrombocytopenic purpura (TTP) are characterized by multiorgan thrombotic microangiopathy. We describe reduction of ADAMTS13 activity and the development of systemic autoimmunity in all 8 children initially diagnosed with acquired noncongenital TTP during an 8.5-year period. Median age at diagnosis was 12.0 years (range, 2.6-17.3 years). ADAMTS13 activity was absent (<5%) in 6 patients; 3 patients had a detected inhibitor. SLE was diagnosed concurrently in 3 patients, and 4 patients were diagnosed within 5 years. Six of the children diagnosed with SLE had absent ADAMTS13 activity at diagnosis. In 6 patients with SLE, immune-mediated nephritis developed by 46 months. All surviving patients with SLE developed antiphospholipid antibodies, including some with a lupus anticoagulant. Patients with SLE did not have TTP recurrences once daily immunosuppressive regimens were started. An evaluation for SLE/APS is warranted in children and adolescents with reduced ADAMTS13 activity and thrombotic microangiopathy.

Atypical presentation of scleroderma in infancy

We present a case of a female child who had developed progressive skin tightening of whole body, sclerodactyly, and severe contracture of all joints with restricted opening of mouth with disease onset at 6 weeks of life. The child also had anemia, failure to thrive, recurrent diarrhea, and ascites. Skin biopsy revealed characteristic histopathological features suggestive of scleroderma. Echocardiography revealed thrombus in the right atrium extending to inferior vena cava. Serological markers (antinuclear antibody, antiscl 70, anti-double-stranded DNA, anticentromere antibody) were negative. To our knowledge, this case of scleroderma with disease onset at 6 weeks of life could possibly be among youngest cases reported in the literature. Also, thrombosis in inferior vena cava in a child with scleroderma is being reported for the first time.

Inefficient clearance of dying cells in patients with SLE: anti-dsDNA autoantibodies, MFG-E8, HMGB-1 and other players

Systemic lupus erythematosus (SLE) is a complex disease resulting from inflammatory responses of the immune system against several autoantigens. Inflammation is conditioned by the continuous presence of autoantibodies and leaked autoantigens, e.g. from not properly cleared dying and dead cells. Various soluble molecules and biophysical properties of the surface of apoptotic cells play significant roles in the appropriate recognition and further processing of dying and dead cells. We exemplarily discuss how Milk fat globule epidermal growth factor 8 (MFG-E8), biophysical membrane alterations, High mobility group box 1 (HMGB1), C-reactive protein (CRP), and anti-nuclear autoantibodies may contribute to the etiopathogenesis of the disease. Up to date knowledge about these key elements may provide new insights that lead to the development of new treatment strategies of the disease.

Cell-bound complement biomarkers for systemic lupus erythematosus: from benchtop to bedside

Systemic lupus erythematosus is arguably the most clinically and serologically diverse autoimmune disease. This article highlights the biomarkers helpful in diagnosing this disease. The authors' own research is presented.

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.

Screening for associated autoimmune disorders in Polish patients with Addison's disease

Autoimmune Addison's disease (AAD) is the main reason of primary adrenal failure. More than a half of patients display additional autoimmune conditions, which represent a considerable clinical concern. This study aimed to investigate the prevalence of concomitant autoimmune disorders in 85 Polish AAD patients (61 females, 24 males). Mean age at AAD onset was 34.6 ± 12.6 years, significantly earlier in males (P < 0.001). Sixty-nine patients presented positive serum antibodies to 21-hydroxylase and shorter AAD duration than those with negative results (P = 0.027). Seventy-three subjects suffered from coexisting autoimmune disorders. Serum autoantibodies against thyreoperoxidase, thyroglobulin, TSH receptor, glutamic acid decarboxylase, insulin, tyrosine phosphatase-like protein IA2, parietal cell H(+)/K(+)-ATPase, intrinsic factor and tissue transglutaminase were detectable in 71.8, 41.2, 4.7, 21.0, 4.9, 2.5, 49.4, 12.0 and 3.5% of patients, respectively. Antinuclear antibodies were found in 12.5%. Thyroid autoimmunity was most common (46 subjects with lymphocytic thyroiditis, 19 with Graves' disease), followed by atrophic gastritis (29.4%), pernicious anaemia (11.8%), hypergonadotropic hypogonadism (8.2%), vitiligo (8.2%), type 1 diabetes (7.1%), celiac disease (3.5%) and alopecia (2.4%). Gender differences were observed only for thyroid autoimmunity. Current study confirms particular tendency of AAD patients to develop other autoimmune disorders. Active search for concomitant conditions is warranted to prevent serious complications.

Comparison of the Farr radioimmunoassay, 3 commercial enzyme immunoassays and Crithidia luciliae immunofluorescence test for diagnosis and activity assessment of systemic lupus erythematosus

BACKGROUNDS

Among anti-double-strand (ds)DNA antibody assays, Farr radioimmunoassay is decreasingly used because it requires radioactive material and is labor intensive. We evaluated the performance of Farr, three commercial enzyme immunoassays (EIAs) and the Crithidia luciliae immunofluorescence test (CLIFT) in systemic lupus erythematosus (SLE).

METHODS

Anti-dsDNA antibodies were determined in 99 SLE patients, 101 healthy subjects, and 53 patients with autoimmune rheumatic diseases.

RESULTS

Farr performed better than the 3 EIAs and CLIFT for the diagnosis of SLE at the manufacturer's cut off and at the cut off set to achieve a specificity of 95%. To achieve a similar level of specificity, some EIAs had a decrease in sensitivity which was dramatic for some tests. Farr was also the best at distinguishing patients with quiescent to mildly active disease from patients with more active disease at the cut off value of 93 IU/ml. Using manufacturer's cut off did not allow distinguishing between patients with quiescent and active SLE.

CONCLUSIONS

Farr was the best global test to assess the level of anti-dsDNA antibodies for both diagnosis and disease activity evaluation in SLE with adequately determined cut off values. Some EIA had low performances limiting their use in decision-making regarding diagnosis and/or treatment.

Prevalence of antinuclear antibodies in 3 groups of healthy individuals: blood donors, hospital personnel, and relatives of patients with autoimmune diseases

Antinuclear antibodies (ANA) are frequently found in healthy populations. To define the prevalence, pattern, and titer of ANA in different groups of the healthy Mexican population, we studied 304 individuals, classified into 3 groups: 104 blood donors, 100 hospital personnel working at The State General Hospital, which included doctors, laboratory technicians, and nurses; and 100 relatives of patient diagnosed either with systemic lupus erythematosus or rheumatoid arthritis, all of them apparently healthy at the time of study. We determined ANA using immunofluorescence microscopy performed on HEp-2 cells. Fluorescence was detected in 165 serum samples (54.3%). The most frequent pattern was the speckled (50.3%). The most frequent dilution was 1:40 (35.4%), followed by 1:80 (13.4%), 1:160 (3.2%), and 1:320 (1.3%).Regarding the results by study group, we found a trend toward higher ANA levels in group 2 (hospital personnel), compared with group 1 (blood donors) and group 3 (relatives of patients), a trend also reflected by the increasing frequency of serum titers of 1:80 and higher (P = 0.074). According to occupation, medical doctors showed a higher incidence of speckled pattern when compared with other occupations (P = 0.022). Medical doctors (n = 75) showed also higher titers of this particular pattern (P = 0.03). In group 3, relatives of patients with systemic lupus erythematosus showed the speckled pattern more frequently than relatives of patients with rheumatoid arthritis, in low titers (P = 0.017). We suggest that ANA tests showing speckled pattern should be at a 1:160 titer or higher to be considered positive; other patterns such as homogeneous, peripheral, or centromeric might be considered positive even at low titers (</=1:40) although this needs investigation.ANA should generally not be tested without clinical indication. Positive ANA finding in the absence of physical signs and symptoms has limited diagnostic utility and should always be interpreted by a rheumatologist, in the context of clinical symptoms and results of laboratory tests for specific autoantibodies. Populations such as doctors and relatives of patients with autoimmune disease tend to presents increased ANA titers.

Automated evaluation of autoantibodies on human epithelial-2 cells as an approach to standardize cell-based immunofluorescence tests

Introduction

Analysis of autoantibodies (AAB) by indirect immunofluorescence (IIF) is a basic tool for the serological diagnosis of systemic rheumatic disorders. Automation of autoantibody IIF reading including pattern recognition may improve intra- and inter-laboratory variability and meet the demand for cost-effective assessment of large numbers of samples. Comparing automated and visual interpretation, the usefulness for routine laboratory diagnostics was investigated.

Methods

Autoantibody detection by IIF on human epithelial-2 (HEp-2) cells was conducted in a total of 1222 consecutive sera of patients with suspected systemic rheumatic diseases from a university routine laboratory (n = 924) and a private referral laboratory (n = 298). IIF results from routine diagnostics were compared with a novel automated interpretation system.

Results

Both diagnostic procedures showed a very good agreement in detecting AAB (kappa = 0.828) and differentiating respective immunofluorescence patterns. Only 98 (8.0%) of 1222 sera demonstrated discrepant results in the differentiation of positive from negative samples. The contingency coefficients of chi-square statistics were 0.646 for the university laboratory cohort with an agreement of 93.0% and 0.695 for the private laboratory cohort with an agreement of 90.6%, P < 0.0001, respectively. Comparing immunofluorescence patterns, 111 (15.3%) sera yielded differing results.

Conclusions

Automated assessment of AAB by IIF on HEp-2 cells using an automated interpretation system is a reliable and robust method for positive/negative differentiation. Employing novel mathematical algorithms, automated interpretation provides reproducible detection of specific immunofluorescence patterns on HEp-2 cells. Automated interpretation can reduce drawbacks of IIF for AAB detection in routine diagnostics providing more reliable data for clinicians.

Prevalence of autoantibodies in SAPHO syndrome: a single-center study of 90 patients

OBJECTIVE

To determine the prevalence of the most often tested autoantibodies in synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome.

METHODS

We identified 90 patients seen in our unit between June 2002 and June 2009, and diagnosed according to the proposed criteria for SAPHO syndrome. Demographic and clinical data were collected as well as immunological results, including antinuclear, antithyroid peroxydase (TPO), antithyroid globulin (Tg), antigastric parietal cell, antismooth muscle, antimitochondria, and anti-liver-kidney microsome (LKM) antibodies. Anticyclic citrullinated peptide (CCP) antibodies were analyzed in 69 patients, antibodies to soluble extractable nuclear antigens in 43, anti-double-stranded DNA (dsDNA) antibodies in 22 [depending on the type of fluorescence of antinuclear antibody (ANA)], and antiendomysium antibodies in 55.

RESULTS

Autoantibodies were found in 20 patients (22.2%): 14 patients (15.5%) had positive ANA (titer >/= 1/160); among them, 10 (11%) patients never took a lupus-inducing drug. Antithyroid antibodies (anti-TPO and/or anti-Tg antibodies) were found in only 3 patients (3.3%). Three patients (3.3%) were positive for antigastric parietal cell antibodies and 4 (4.4%) were weakly positive for antismooth muscle antibodies. Antimitochondria and LKM antibodies were negative in all 90 patients. Anti-CCP and anti-dsDNA antibodies were negative in the 69 and 22 patients tested, respectively. One out of 43 patients (2.3%) had anti-SSA antibodies. Antiendomysium antibodies were negative in the 55 patients tested.

CONCLUSION

Our study indicates an increased prevalence of autoantibodies in SAPHO syndrome, with no specific profile. We failed to confirm the reports of an increased prevalence of antithyroid antibodies. These results tend to support a link between autoimmunity and SAPHO syndrome.

Lymphocyte-bound complement activation products as biomarkers for diagnosis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is frequently misdiagnosed due to the lack of definitive diagnostic tests. The purpose of this study was to determine specifically whether complement activation products (CAP) are deposited on lymphocytes of SLE patients and whether lymphocyte-bound CAP (LB-CAP) may serve as novel biomarkers for the diagnosis of SLE. We conducted a cross-sectional study of 224 patients with SLE, 179 patients with other diseases, and 114 healthy controls. LB-CAP on peripheral blood lymphocytes was measured by flow cytometry. Diagnostic utility of LB-CAP was determined by receiver operating characteristic (ROC) analysis. Significantly elevated levels of C4d and C3d were detected specifically on T and B lymphocytes (designated T-C4d, T-C3d, B-C4d, and B-C3d) of SLE patients. As diagnostic tools, T-C4d and B-C4d, respectively, were 56% sensitive/80% specific and 60% sensitive/82% specific in differentiating SLE from other diseases. Moreover, compared with measurement of anti-dsDNA, serum C3, or serum C4, measurement of T-C4d/B-C4d was significantly more sensitive in identifying SLE patients during a single clinic visit. This is the first investigation of lymphocytes bearing complement activation products in human disease. T-C4d and B-C4d have high diagnostic sensitivity and specificity for SLE and may have added value to current laboratory tests for SLE diagnosis.

Antinuclear antibodies in recurrent idiopathic pericarditis: prevalence and clinical significance

BACKGROUND

A positive result for antinuclear antibodies (ANA), often as a fortuitous observation, may be cause for concern in idiopathic recurrent pericarditis (IRP), nevertheless data are lacking on their prevalence and clinical significance. This study is sought to investigate the prevalence and clinical significance of ANA in IRP.

METHODS

ANA titres were assessed in consecutive patients with recurrent pericarditis, and matched healthy controls. Baseline and follow-up data were recorded and compared according to ANA results.

RESULTS

A total of 145 consecutive patients with recurrent pericarditis were studied: 122 patients with IRP, 23 patients with pericarditis due to known etiologies (rheumatologic diagnoses and postpericardiotomy syndrome), and 122 healthy controls. ANA were detected in 53 of 122 (43.4%) patients with IRP, and in only 12 of 122 (9.8%) controls (p<0.001). Low titres (1/40-1/80) were found in the majority of cases, while moderate positivity (1/160-1/320) was more common in patients with a known rheumatic disease (26.7% vs. 5.7%; p=0.020). High concentrations of ANA (> or =1/640) were not recorded. Women were at increased risk for ANA (OR 2.22 95%CI 1.07-4.60; p=0.033). During a mean follow-up of 32 months, complications and new diagnoses were similar in patients with or without ANA positivity.

CONCLUSIONS

Low-positive titres are more common in patients with IRP than in controls, suggesting a possible autoimmune pathogenesis. Nevertheless, they are often a clinically non-specific finding. Routine serologic testing for ANA suggests a source for recurrent pericarditis in less than 10% of cases, and in these cases other evidence typically suggests the underlying disease.

Immune complex clearance by monocytes and macrophages in systemic lupus erythematosus

During the last 30 years more than 700 patients with systemic lupus erythematosus (SLE) have been treated in our department with their data analyzed. Here we focus on circulating immune complex (CIC) and its clearance. We demonstrated, microscopically, that the uptake of IgG sensitized erythrocytes (EA), via monocytes (Mo) of SLE patients, was elevated and correlated with the high CIC content. The in Vivo clearance of sensitized autolog E, and the in vitro degradation rate of soluble IC by Mo of SLE patients were decreased. This discrepancy could be explained by the molecular heterogeneity of FcgammaR being recognized lately. The high FcgammaRI expression and the low FcgammaRII and FcgammaRIII expression were detected by monoclonal antibodies (mAb) on Mo in SLE. The EA bound mostly to FcgammaRI, FcgammaRII and FcgammaRIII have a role in phagocytosis. The decreased receptor expression and function correlated with the disease activity and renal involvement. The shedding of receptors may cause a decrease on Mo surface, with the soluble FcRII and FcgammaRIII levels being elevated in serum of SLE patients. The mannose binding receptors, which play a role in the phagocytosis of apoptotic cells in SLE, were also decreased on Mo of SLE patients.

Idiopathic nonspecific interstitial pneumonia: lung manifestation of undifferentiated connective tissue disease?

RATIONALE

The American Thoracic Society/European Respiratory Society International Consensus Classification panel identified the clinical entity idiopathic nonspecific interstitial pneumonia (NSIP) as a provisional diagnosis and recommended further study.

OBJECTIVES

We hypothesized that idiopathic NSIP is an autoimmune disease and the lung manifestation of undifferentiated connective tissue disease (UCTD), a recently described, distinct entity.

METHODS

We studied 28 consecutive patients with idiopathic interstitial pneumonia (IIP) enrolled in the University of California, San Francisco Interstitial Lung Disease Center who met prespecified criteria for UCTD, as follows: at least one clinical manifestation of connective tissue disease, serologic evidence of systemic inflammation in the absence of clinical infection, and absence of sufficient American College of Rheumatology criteria for another connective tissue disease. Medical record reviews, evaluation of radiographs, and scoring of lung biopsies were performed. The control group consisted of all other patients (n = 47) with IIP who did not meet the UCTD criteria.

MEASUREMENTS AND MAIN RESULTS

The patients with UCTD were more likely to be women, younger, and nonsmokers than the IIP control subjects. Compared with the control group, patients with UCTD-ILD were significantly more likely to have ground-glass opacity on high-resolution computed tomography (HRCT) and NSIP pattern on biopsy, and less likely to have honeycombing on HRCT or usual interstitial pneumonia on biopsy. At our center, the majority of patients classified as idiopathic NSIP (88%) met the criteria for UCTD.

CONCLUSIONS

Most patients diagnosed with idiopathic NSIP meet the case definition of UCTD. Furthermore, these results show that the clinical entity idiopathic NSIP is different from idiopathic pulmonary fibrosis and appears to be an autoimmune disease.

Labordiagnostik bei systemischer Sklerose

For systemic sclerosis, laboratory tests can play a supplementary role to clinical investigations, imaging techniques and functional tests. Typical autoantibodies support early diagnosis and help in assigning patients to subgroups of the disease; negative results for antinuclear antibodies suggest exclusion of the diagnosis. To detect organ involvement and comorbidity, the laboratory contributes by clinical chemistry, in certain cases by histopathological findings and by the cytological assessment of broncho-alveolar lavage fluid. Inflammatory parameters are of minor importance. Multiple autoantibody determinations in the course of the disease are not yet helpful. Numerous additional laboratory parameters are of value for investigating pathogenesis, but have not yet been generally introduced into the routine diagnostics of systemic sclerosis.

Antinuclear antibodies measured by enzyme immunoassay in patients with systemic lupus erythematosus: relation to disease activity

To evaluate the correlation between measurements of antinuclear antibodies serum levels by enzyme immunoassay (ANA-EIA), and the degree of systemic lupus erythematosus disease activity. To retest the performance of the test compared to measurement of antinuclear antibodies by immunofluorescence (ANA-IIF). Eighty-five sera from 71 patients with SLE were tested. Demographic, clinical, laboratory, and SLEDAI status were collected. The sera were tested for ANA-EIA and by ANA-IIF at 1:40 and 1:160 dilutions. Serum levels of ANA-EIA were compared to the overall SLEDAI score and to each of its components. A SLEDAI score of > or =6 was considered clinically significant. The sera of fifty-one healthy volunteers served as controls. Serum levels of ANA-EIA were significantly higher in patients with a SLEDAI score of > or =6 compared to the group of patients with a SLEDAI score of <6 (P = 0.004). High serum levels of ANA-EIA correlated significantly with elevated anti DS-DNA antibodies (P < 0.001), low C(3) or C(4) levels (P < 0.001), pyuria (P < 0.011), arthritis (P = 0.019), and new rash (P = 0.019). Levels of ANA-EIA were significantly higher in patients tested positive by IIF compared to those who tested negative. Higher serum levels of ANA-EIA correlated with clinically significant disease activity in patients with SLE. Higher serum levels of ANA-EIA also correlated with some single items of the SLEDAI. The results also reiterated the validity of ANA-EIA testing in patients with SLE. Further longitudinal studies are needed in order to test the hypothesis that serum ANA-EIA levels might reflect fluctuations in disease activity.

Macrophage migration inhibitory factor promoter polymorphisms and the clinical expression of scleroderma

OBJECTIVE

To investigate the potential association between functional polymorphisms in the gene for the innate mediator, macrophage migration inhibitory factor (MIF), and the clinical expression of systemic sclerosis (SSc).

METHODS

Genomic DNA samples and clinical data were collected from the Scleroderma Family Registry and DNA Repository at the University of Texas Health Science Center at Houston. A total of 740 subjects were studied; 203 of them had diffuse cutaneous SSc (dcSSc), 283 had limited cutaneous SSc (lcSSc), and the remaining 254 healthy subjects served as controls. Association analyses were performed on the whole data set and on patient and sex subsets. Significant relationships were determined between clinical variables and MIF polymorphisms for each disease subtype in the studied groups.

RESULTS

The frequency of the -173*C MIF allele, which was previously reported to be associated with high production of MIF, was lower in the lcSSc group (12.6%) than in the dcSSc (19.2%) or control (18.5%) groups (P = 0.010 and P = 0.011, respectively). Haplotype analysis for 2 closely linked polymorphisms in the MIF promoter showed that in white subjects with lcSSc or dcSSc, the lcSSc population had a significantly lower representation of the high-expression MIF haplotype defined by -173*C and -794 with 7 CATT repeats (C7) (P = 0.015, odds ratio 1.94 [95% confidence interval 1.14-3.32]). Fibroblasts encoding the C7 MIF haplotype were observed to produce more MIF upon in vitro stimulation than those with a non-C7 haplotype.

CONCLUSION

Functional promoter polymorphisms in the MIF gene affect the clinical presentation of SSc. The proinflammatory haplotype defined by C7 is underrepresented in patients with lcSSc.

Autoantibodies to intracellular autoantigens and their B-cell epitopes: molecular probes to study the autoimmune response

A common laboratory finding in systemic autoimmune diseases is the presence of autoantibodies against intracellular autoantigens. Although their pathogenesis is not fully understood, autoantibodies are important tools for establishing diagnosis, classification, and prognosis of autoimmune diseases. Autoantibodies mainly target multicomponent complexes containing both protein antigens and (ribo)-nucleic acid(s), such as the spliceosome or Ro/La RNPs. In this review, we address the main characteristics and the clinical value of the main autoantibody types with respect to their disease association, and we describe the corresponding autoantigens, their biologic function, and their B-cell antigenic determinants (epitopes). The structural characteristics and clinical associations of these epitopes, and their utility as tools to investigate the autoimmune response, are discussed in detail. New insights into the pathogenetic role of epitopes in systemic autoimmunity are also examined. In this regard, using the defined structures of the B-cell antigenic epitopes, complementary epitopes can be designed according to the "molecular recognition" theory. These complementary epitopes can be used as probes to study pathogenetic and immunoregulatory aspects of the anti-idiotypic response. The origin of humoral autoimmunity and the spreading of the epitopes in systemic lupus erythematosus are also discussed. Finally, the ability of post-translational modifications to induce autoreactive immune attack via the generation of neo-epitopes is summarized.

Computer-assisted pattern recognition of autoantibody results

Immunoassay-based anti-nuclear antibody (ANA) screens are increasingly used in the initial evaluation of autoimmune disorders, but these tests offer no "pattern information" comparable to the information from indirect fluorescence assay-based screens. Thus, there is no indication of "next steps" when a positive result is obtained. To improve the utility of immunoassay-based ANA screening, we evaluated a new method that combines a multiplex immunoassay with a k nearest neighbor (kNN) algorithm for computer-assisted pattern recognition. We assembled a training set, consisting of 1,152 sera from patients with various rheumatic diseases and non-diseased patients. The clinical sensitivity and specificity of the multiplex method and algorithm were evaluated with a test set that consisted of 173 sera collected at a rheumatology clinic from patients diagnosed by using standard criteria, as well as 152 age- and sex-matched sera from presumably healthy individuals (sera collected at a blood bank). The test set was also evaluated with a HEp-2 cell-based enzyme-linked immunosorbent assay (ELISA). Both the ELISA and multiplex immunoassay results were positive for 94% of the systemic lupus erythematosus (SLE) patients. The kNN algorithm correctly proposed an SLE pattern for 84% of the antibody-positive SLE patients. For patients with no connective tissue disease, the multiplex method found fewer positive results than the ELISA screen, and no disease was proposed by the kNN algorithm for most of these patients. In conclusion, the automated algorithm could identify SLE patterns and may be useful in the identification of patients who would benefit from early referral to a specialist, as well as patients who do not require further evaluation.

The effect of TNFalpha blockade on the antinuclear antibody profile in patients with chronic arthritis: biological and clinical implications

Since the first proof of efficacy of TNFalpha blockade, both the number of patients treated worldwide and the number of indications for treatment with TNFalpha blockers have grown steadily. Surprisingly, the profound immunomodulation induced by anti-TNFalpha therapy is associated with a relatively low incidence of immune-related complications such as lupus-like syndromes and demyelinating disease. This contrasts sharply with the prominent induction of autoantibodies such as antinuclear antibodies (ANA) and anti-dsDNA antibodies during TNFalpha blockade. Although this phenomenon has been recognized for several years, the clinical and biological implications are not yet fully understood. In this review, recent studies analysing the effect of TNFalpha blockade (infliximab and etanercept) on the ANA profile in autoimmune arthritis will be discussed. Taken together, these reports indicate that the prominent ANA and anti-dsDNA autoantibody response is 1) not a pure class effect of TNFalpha blockers, 2) independent of the disease background, 3) largely restricted to the induction of short-term IgM anti-dsDNA antibodies, and 4) not associated with other serological or clinically relevant signs of lupus. Nevertheless, a careful follow-up of patients treated with TNFalpha blockers remains mandatory, including monitoring for lupus-like characteristics.

Fator antinúcleo na dermatologia

Trata-se de artigo de revisão e atualização sobre a pesquisa dos anticorpos antinucleares, em especial do fator antinúcleo, em que são abordados os aspectos históricos, epidemiológicos, fisiopatogenia, métodos de identificação, suas especificidades e interpretação, correlacionando-os com sua aplicabilidade na prática clínica do dermatologista e do clínico geral.

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

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

Laboratory testing in the rheumatic diseases: a practical review

Laboratory testing for the rheumatic diseases can allow for rapid diagnosis and appropriate management, while false-positive tests can lead to inappropriate management and unnecessary concern for the patient. An evaluation of laboratory testing for rheumatic illnesses is discussed, including the well-known acute phase proteins, the use of ANA in screening, and the newer antibodies which may potentially allow for an earlier diagnosis. A thorough history and examination are arguably the best screening tests. Clinicians should be judicious in their use of laboratory testing, and should only do so in an attempt to further refine the diagnosis.