Antinuclear antibody screening in this new millennium: farewell to the microscope?

Emerging technologies in autoantibody testing for rheumatic diseases

Testing for the presence of antinuclear antibodies (ANAs) is a key step in the diagnosis of systemic lupus erythematosus (SLE) and other systemic autoimmune rheumatic diseases (SARD). The standard slide-based indirect immunofluorescence (IIF) test is widely used, but is limited by a relative lack of specificity for SLE and not all SARD-ANAs are detected. Alternative immunoassays that might offer enhanced diagnostic and prognostic information have evolved, and some of these have entered clinical practice. This review summarizes the current state of ANA testing and multiplex techniques for detecting other autoantibodies, the possibility of point-of-care testing, and approaches for applications in early disease stages.

Chemiluminescent immunoassay technology: what does it change in autoantibody detection?

Diagnostic technology is rapidly evolving, and over the last decade, substantial progress has been made even for the identification of antibodies, increasingly approaching this type of diagnostic to that of automated clinical chemistry laboratory. In this review, we describe the analytical and diagnostic characteristics of chemiluminescence technology in its strength and in its applicability for a more rapid and accurate diagnosis of autoimmune diseases. The wide dynamic range, greater than that of immunoenzymatic methods, the high sensitivity and specificity of the results expressed in quantitative form, the high degree of automation and the clinical implications related to the reduction in the turnaround time, and the ability to run a large number of antibody tests (even of different isotypes), directed towards large antigenic panels in random access mode, make this technology the most advanced in the clinical laboratory, with enormous repercussions on the workflow and on the autoimmunology laboratory organisation. Further improvements are expected in the coming years with the development of new analytical platforms such as the flow-injection chemiluminescent immunoassay, the two-dimensional resolution for chemiluminescence multiplex immunoassay and the magnetic nanoparticles chemiluminescence immunoassay, which will likely result in additional increases in the clinical efficacy of antibody tests.

Autoantibody Detection Using Multiplex Technologies

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

How should a district general hospital immunology service screen for anti-nuclear antibodies? An 'in-the-field' audit

Anti-nuclear antibody (ANA) testing assists in the diagnosis of several immune-mediated disorders. The gold standard method for detection of these antibodies is by indirect immunofluorescence testing on human epidermoid laryngeal carcinoma (HEp-2) cells. However, many laboratories test for these antibodies using solid-phase assays such as enzyme-linked immunosorbent assay (ELISA), which allows for higher throughput testing at reduced cost. In this study, we have audited the performance of a previously established ELISA assay to screen for ANA, making comparison with the gold standard HEp-2 immunofluorescence test. A prospective and unselected sample of 89 consecutive ANA test requests by consultant rheumatologists were evaluated in parallel over a period of 10 months using both tests. ELISA and HEp-2 screening assays yielded 40 (45%) and 72 (81%) positive test results, respectively, demonstrating lack of concordance between test methods. Using standard and clinical samples, it was demonstrated that the ELISA method did not detect several ANA with nucleolar, homogeneous and speckled immunofluorescence patterns. None of these ELISA(NEG) HEp-2(POS) ANA were reactive with a panel of six extractable nuclear antigens or with double-stranded DNA. Nonetheless, 13 of these samples (15%) originated from patients with recognized ANA-associated disease (n = 7) or Raynaud's phenomenon (n = 6). We conclude that ELISA screening may fail to detect clinically relevant ANA that lack defined specificity for antigen.

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

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

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

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

Biomarkers of Chronic Uveitis in Juvenile Idiopathic Arthritis: Predictive Value of Antihistone Antibodies and Antinuclear Antibodies

Objective.

To study the predictive value of antinuclear autoantibody (ANA) tests and antihistone antibodies (AHA) as risk factors for development of chronic asymptomatic uveitis of insidious onset in juvenile idiopathic arthritis (JIA).

Methods.

ANA by indirect immunofluorescence using HEp-2 cells (IF-ANA), ELISA for ANA (E-ANA), and AHA were analyzed in sera of 100 children with recent-onset JIA and in 58 control sera. Clinical features, including age at onset, JIA subgroup, and presence of uveitis, were recorded in this prospective population-based cohort study.

Results.

E-ANA was positive in 4 of the 100 sera, and was not associated with uveitis. Chronic uveitis developed in 16 children with JIA: in 14 of 68 positive for IF-ANA ≥ 80, and in 13 of 44 positive for AHA ≥ 8 U/ml. IgM/IgG AHA were found in higher proportions in children with uveitis (mean 12.4 U/ml) than in those with JIA and no uveitis (mean 6.9 U/ml) or in healthy controls (mean 4.3 U/ml).

Conclusion.

No association was found between E-ANA and uveitis, and most IF-ANA-positive sera were E-ANA-negative. E-ANA is not clinically relevant in this setting and should never be used to determine frequencies of eye examinations to detect new uveitis in JIA. AHA ≥ 8 U/ml, IF-ANA titer ≥ 320, and young age at onset of arthritis were significant predictors for development of chronic uveitis. The diagnostic value of AHA ≥ 8 U/ml as a biomarker of chronic uveitis in JIA is very similar to IF-ANA ≥ 80.

The Influence of the 1997 Updated Classification Criteria for Systemic Lupus Erythematosus: Epidemiology, Disease Presentation, and Patient Management

Objective.

The 1997 update of the American College of Rheumatology classification criteria (ACR97) for systemic lupus erythematosus (SLE) has not been validated. We determined to what extent their introduction influenced the epidemiology and clinical characteristics of the disease in northern Norway.

Methods.

Annual incidence and point-prevalence rates, clinical manifestations, and outcome were determined in an inception cohort of patients with SLE in northern Norway, included between 1996 and 2006, using ACR97 criteria (97acr). These findings were compared with a cohort from the same area enrolled 1978–1995 using the 1982 revised criteria ACR82 (82acr).

Results.

The mean annual incidence of SLE was 3.00 for cohort 97acr (n = 58) versus 2.63 for cohort 82acr (n = 81) (p = 0.5). All patients in the 97acr cohort also fulfilled the 1982 criteria; however, significantly fewer patients presented with discoid rash [odds ratio (OR) 0.31)], arthritis (OR 0.24), renal (OR 0.28) or hematological disorder (OR 0.27), and significantly more with anti-dsDNA (OR 2.57) and antiphospholipid antibodies (OR 27.9). Initial treatment with intravenous pulse methylprednisolone (OR 9.23), azathioprine (OR 6.32), and low-dose aspirin (OR 20.9) was increased in cohort 97acr. Five- (95.2%) and 10-year survival (91.9%) rates were also improved for cohort 97acr.

Conclusion.

The ACR97 criteria set has construct validity compared to the ACR82 criteria set. SLE incidence remains unchanged in northern Norway, but a significant reduction of renal disease and further improvements in survival rates occurred simultaneously with increased serological surveillance with ELISA-based assays and early immunosuppressive and anticoagulant therapy.

Alpha-actinin-binding antibodies in relation to systemic lupus erythematosus and lupus nephritis

This study investigated the overall clinical impact of anti-α-actinin antibodies in patients with pre-selected autoimmune diseases and in a random group of anti-nuclear antibody (ANA)-positive individuals. The relation of anti-α-actinin antibodies with lupus nephritis and anti-double-stranded DNA (anti-dsDNA) antibodies represented a particular focus for the study. Using a cross-sectional design, the presence of antibodies to α-actinin was studied in selected groups, classified according to the relevant American College of Rheumatology classification criteria for systemic lupus erythematosus (SLE) (n = 99), rheumatoid arthritis (RA) (n = 68), Wegener's granulomatosis (WG) (n = 85), and fibromyalgia (FM) (n = 29), and in a random group of ANA-positive individuals (n = 142). Renal disease was defined as (increased) proteinuria with haematuria or presence of cellular casts. Sera from SLE, RA, and Sjøgren's syndrome (SS) patients had significantly higher levels of anti-α-actinin antibodies than the other patient groups. Using the geometric mean (± 2 standard deviations) in FM patients as the upper cutoff, 20% of SLE patients, 12% of RA patients, 4% of SS patients, and none of the WG patients were positive for anti-α-actinin antibodies. Within the SLE cohort, anti-α-actinin antibody levels were higher in patients with renal flares (p = 0.02) and correlated independently with anti-dsDNA antibody levels by enzyme-linked immunosorbent assay (p < 0.007) but not with other disease features. In the random ANA group, 14 individuals had anti-α-actinin antibodies. Of these, 36% had SLE, while 64% suffered from other, mostly autoimmune, disorders. Antibodies binding to α-actinin were detected in 20% of SLE patients but were not specific for SLE. They correlate with anti-dsDNA antibody levels, implying in vitro cross-reactivity of anti-dsDNA antibodies, which may explain the observed association with renal disease in SLE.

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.

Present and future of the autoimmunity laboratory

At present, autoimmunity laboratories are very dynamic owing to the constant and increasing availability of new tests, mainly due to the detection of new autoantibodies. The main characteristic of the autoimmunity laboratory and the one that differentiates it from other laboratories that use immunoassays as basic techniques is that it determines antibodies (autoantibodies) and not antigens. For this reason, immunoassay techniques must employ antigens as reagents. Indirect immunofluorescence has and continues to be a basic technique in autoimmunity studies. However, over the last few years, a significant trend at autoimmunity laboratories has been the gradual replacement of immunofluorescence microscopy by immunoassay. Of the several different forms of immunoassay, the enzyme-linked immunosorbent assay (ELISA) format is the one most used in autoimmunity laboratories. Recombinant DNA technology has allowed the production of large quantities of antigens for autoantibody analysis. Flow cytometry for the analysis of microsphere-based immunoassays allows the simultaneous measurement of several autoantibodies. Likewise, autoantigen microarrays provide a practical means to analyse biological fluids in the search for a high number of autoantibodies. We are now at the beginning of an era of multiplexed analysis, with a high capacity of autoantibody specificities. Future trends in this field include immunoassays with greater analytical sensitivity, simultaneous multiplexed capability, the use of protein microarrays, and the use of other technologies such as microfluidics.

Laboratory screening of connective tissue diseases by a new automated ENA screening assay (EliA Symphony) in clinically defined patients

BACKGROUND

The measurement of antinuclear antibodies (ANA) is used in the autoimmune laboratory for the screening of connective tissue diseases (CTD). ANA measurements are mainly performed by indirect immunofluorescence (IIF) on HEp-2 cells or by enzyme immunoassay (EIA). The objective of this study was to clinically evaluate an automated EIA for extractable nuclear antigens (ENA) which lacks anti-dsDNA for the screening of CTD.

METHODS

The study involved a total of 170 serum samples, 54 from patients with CTD, 26 from patients with other autoimmune diseases, and 90 from patients with non-autoimmune diseases. For all sera, ANA detection was performed by IIF and by EliA Symphony (Pharmacia Diagnostics, Freiburg, Germany), an ENA screening which detects the following autoantibodies: SSA/Ro, SSB/La, U1RNP (70 kDa, A, C), Scl-70, JO-1, centromere B and Sm. Also, anti-dsDNA (EliA dsDNA, Pharmacia Diagnostics, Freiburg, Germany) was measured on all samples. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), efficiency, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were calculated.

RESULTS

Diagnostic efficiency was similar for IIF (82.6%) and EliA Symphony (82.3%), as well as PLR (6.5 for IIF, and 7.3 for Eli Symphony), and NLR (0.35 for IIF, and 0.41 for EliA Symphony). The combined measurement of EliA Symphony and dsDNA increased sensitivity but not PLR. Area under receiver operator characteristic (ROC) curve was similar for IIF (0.847) and EliA Symphony (0.823).

CONCLUSIONS

The results of the study demonstrate that EliA Symphony solely or combined with anti-dsDNA detection has an efficiency similar to HEp-2 cells IIF with a cut-off of 1:160 for the diagnosis of CTD.

Detection of Antinuclear Antibodies by Solid-Phase Immunoassays and Immunofluorescence Analysis

Background: Antinuclear antibodies (ANAs) are associated with several inflammatory rheumatic diseases. The aim of the present work was to evaluate enzyme immunoassays (EIAs) and compare them with classic immunofluorescent analysis (IFA) for the detection of ANA.

Methods: Seven enzyme immunoassays were used in this study. All assays were applied as described by the manufacturers. Three populations were included in the study: (a) a population of patients with well-established autoimmune inflammatory disease (n = 102); (b) a population in which a rheumatic disease was diagnosed up to 5 years after an IFA was performed (n = 164); and (c) a population of consecutive outpatients suspected to have a rheumatic disease (n = 101). The current clinical diagnoses of the patients served as the standard against which performance of the assays was evaluated.

Results: In patients with well-established rheumatic disorders, the newly developed EIA in which HEp-2 extracts were included had sensitivities and specificities comparable to or in some instances better than the IFA. The assays without HEp-2 extracts included had significantly lower sensitivities and specificities. In the outpatient population, up to 51% of patients had positive ANA tests that did not correspond to classic ANA-associated disease. However, in the assays in which the HEp-2 extracts were not included, the false-positive rate was &lt;10%. The false-negative rate judged against IFA differed from assay to assay and disease to disease and was mostly &lt;10%.

Conclusions: In this study, the sensitivities of EIAs and IFA were largely comparable. However, EIAs without HEp-2 extracts included had a low sensitivity but a high specificity, particularly in nonselected populations. The choice of test is highly dependent on the clinical setting in which the ANA test is to be used and on laboratory policy.

Methods of choice for diagnostic antinuclear antibody (ANA) screening

OBJECTIVES

To evaluate and compare the performances of three enzyme-immunoassays (EIAs) and a double radial immunodiffusion (DRID) test in addition to immunofluorescence (IF) microscopy for routine laboratory screening of patient sera sent for antinuclear antibody (ANA) analysis.

METHODS

3079 consecutive patient sera sent for routine testing of ANA were analysed by IF microscopy on HEp-2 cells (IF-ANA), three different ANA-EIAs, and a DRID test for antibodies against extractable nuclear antigens. The IF-ANA and DRID tests were regarded as reference methods.

RESULTS

By IF-ANA and/or DRID, 375 sera (12%) turned out ANA-positive. A further 171 sera (6%) were positive by EIA, but could not be confirmed either by IF microscopy or DRID. 32 of the 375 ANA-positive (9%) sera were negative by IF microscopy, but had precipitating antibodies against Ro/SS-A (52 and/or 60 kD).

CONCLUSIONS

Different assays for ANA analysis give overlapping results to a certain extent, but are by no means interchangeable. Thus, different ANA tests reflect different aspects of these autoantibodies. The diagnostic utility of ANA testing still mainly refers to IF-microscopy and precipitin tests. IF-ANA should not be abandoned as the golden standard in clinical routine, until diagnostic and classification criteria for systemic lupus erythematosus and other systemic inflammatory autoimmune diseases have been revised. However, in addition we strongly advocate that a specific test for anti-Ro/SS-A antibodies is always included.

Screening of antinuclear antibodies: comparison between enzyme immunoassay based on nuclear homogenates, purified or recombinant antigens and immunofluorescence assay

Current clinical practice considers antinuclear antibody (ANA) testing as a screening test; this has a major impact on laboratory work with a growing volume of analyses that need to be performed rapidly, to maintain good specificity and sensitivity. Ongoing discussions have been raised in order to identify the best technology to use in ANA screening, taking into account both clinical and economical implications. The aim of our study was to compare three different enzyme immunoassays (EIA) with immunofluorescence (IF) assay in order to identify which test is better for use as a screening test. The study was performed on 473 sera and the three different EIA tests were based on nuclear homogenates from HeLa cells, purified antigens from HEp-2 cells and recombinant antigens, respectively. The concordance between EIA-ANA and IF-ANA techniques, determined by the κ statistic, was acceptable, but not complete, and discrepancies between both EIA-positive/IF-negative samples and IF-positive/EIA-negative were found. Both methods show interesting diagnostic abilities, however, the IF-ANA assay seems to be the first choice test in a well-standardized immunofluorescence laboratory with experienced microscopists, whereas the EIA test might be useful especially in large-scale ANA screening.

Immunofluorescence versus ELISA for the detection of antinuclear antigens

Determining the presence and specificity of antinuclear antigens (ANA) is a challenge to a laboratory involved in the diagnosis of connective tissue disease (CTD). The immunofluorescent technique (IF), once considered the gold standard, is more and more displaced by ELISA. ELISA can be fully automated and the interpretation does not require the extensive experience needed in IF. However, literature in which both techniques are compared does not give unequivocal conclusions that ELISA indeed performs better. The clue as to which technique is best in the cascade testing of ANA, is given by its clinical value, not only by its technical and logistic performance. Selective test ordering is strongly recommended to increase the predictive value of these tests. The pros and cons of both techniques are discussed.