Impact of external quality assessment on antinuclear antibody detection performance

Detection of antinuclear antibodies: recommendations from EFLM, EASI and ICAP

OBJECTIVES

Antinuclear antibodies (ANA) are important for the diagnosis of various autoimmune diseases. ANA are usually detected by indirect immunofluorescence assay (IFA) using HEp-2 cells (HEp-2 IFA). There are many variables influencing HEp-2 IFA results, such as subjective visual reading, serum screening dilution, substrate manufacturing, microscope components and conjugate. Newer developments on ANA testing that offer novel features adopted by some clinical laboratories include automated computer-assisted diagnosis (CAD) systems and solid phase assays (SPA).

METHODS

A group of experts reviewed current literature and established recommendations on methodological aspects of ANA testing. This process was supported by a two round Delphi exercise. International expert groups that participated in this initiative included (i) the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group "Autoimmunity Testing"; (ii) the European Autoimmune Standardization Initiative (EASI); and (iii) the International Consensus on ANA Patterns (ICAP).

RESULTS

In total, 35 recommendations/statements related to (i) ANA testing and reporting by HEp-2 IFA; (ii) HEp-2 IFA methodological aspects including substrate/conjugate selection and the application of CAD systems; (iii) quality assurance; (iv) HEp-2 IFA validation/verification approaches and (v) SPA were formulated. Globally, 95% of all submitted scores in the final Delphi round were above 6 (moderately agree, agree or strongly agree) and 85% above 7 (agree and strongly agree), indicating strong international support for the proposed recommendations.

CONCLUSIONS

These recommendations are an important step to achieve high quality ANA testing.

Properties of Uncommon Indirect Immunofluorescence Staining Patterns Determined during Antinuclear Antibody Detection on HEp-2 Cells

In this study, we aimed to assess the prevalence of uncommon staining patterns found during testing for the presence of antinuclear antibodies (ANA) and to determine their association with certain antibodies and clinical diagnoses. Presence of ANA and the staining pattern was determined in 10955 samples using indirect immunofluorescence (IIF) on HEp-2 cells. ANA-positive samples were assessed for presence of 14 specific antibody types using a microbead based system. Demographic data (age, sex) and clinical diagnoses were collected from the referral documentation. Particular staining patterns were then compared with a representative comparison group comprised of samples with common staining patterns using these criteria. There were 22 patterns present in less than 3% of samples each and these were jointly present in 42.43% of ANA-positive samples. Specific antibodies were found in proportions similar to the comparison group (46.06%) and varied significantly between patterns. Likewise, there were significant differences in antibody distribution in particular patterns. Some patterns were associated with presence of rheumatic diseases or inflammatory arthropathies, while in others there was a concurrent diagnosis of liver disease, or a neoplastic process. Many of the uncommon IIF patterns have distinctive characteristics that warrant further investigation in order to determine their role in diagnosing various diseases, not limited only to the illnesses of the rheumatic spectrum. IIF on HEp-2 cells remains an irreplaceable method because of the diversity of ANA, only a number of which can be detected using other standardised methods.

Heterogeneous ensemble with information theoretic diversity measure for human epithelial cell image classification

In this work, we propose a heterogeneous committee (ensemble) of diverse members (classification approaches) to solve the problem of human epithelial (HEp-2) cell image classification using indirect Immunofluorescence (IIF) imaging. We hypothesize that an ensemble involving different feature representations can enable higher performance if individual members in the ensemble are sufficiently varied. These members are of two types: (1) CNN-based members, (2) traditional members. For the CNN members, we have employed the well-established ResNet, DenseNet, and Inception models, which have distinctive salient aspects. For the traditional members, we incorporate class-specific features which are characterized depending on visual morphological attributes, and some standard texture features. To select the members which are discriminating and not redundant, we use an information theoretic measure which considers the trade-off between individual accuracies and diversity among the members. For all selected members, a compelling fusion required to combine their outputs to reach a final decision. Thus, we also investigate various fusion methods that combine the opinion of the committee at different levels: maximum voting, product, decision template, Bayes, Dempster-Shafer, etc. The proposed method is evaluated using ICPR-2014 data which consists of more images than some previous datasets ICPR-2012 and demonstrate state-of-the-art performance. To check the effectiveness of the proposed methodology for other related datasets, we test our methodology with newly compiled large-scale HEp-2 dataset with 63K cell images and demonstrate comparable performance even with less number of training samples. The proposed method produces 99.80% and 86.03% accuracy respectively when tested on ICPR-2014 and a new large-scale data containing 63K samples. Graphical Abstract Overview of the proposed methodology.

Standardization and Quality Assessment Under the Perspective of Automated Computer-Assisted HEp-2 Immunofluorescence Assay Systems

The recent availability of automated computer-assisted diagnosis (CAD) systems for the reading and interpretation of the anti-nuclear antibody (ANA) test performed with the indirect immunofluorescence (IIF) method on HEp-2 cells, has improved the reproducibility of the results and initiated a process of harmonization of this test. Furthermore, CAD systems provide quantitative expression of fluorescence intensity, allowing the introduction of objective quality control procedures to the monitoring of the entire process. The calibration of the reading systems and the automated image interpretation are essential prerequisites for obtaining reproducible and harmonized IIF test results and form the basis for standardization, regardless of the computer algorithms used in the different systems. The use of automated CAD systems, facilitating control procedures, represents a step forward for the quality certification of the laboratory.

Long-Term Variability in Immunofluorescence Titer of Antibodies to Nuclear Antigens Observed in Clinical Laboratory Proficiency Testing Surveys

CONTEXT.—

Presence of antibodies to nuclear antigens (ANAs) above a threshold titer is an important diagnostic feature of several autoimmune diseases, yet titers reported vary between laboratories. Proficiency survey results can help clarify factors contributing to the variability.

OBJECTIVE.—

To determine the contribution of HEp-2 ANA kits from different manufacturers to the variation in titers, and assess whether the differences between kits are consistent over the long term.

DESIGN.—

HEp-2 ANA titers reported by laboratories participating in the external quality assessment proficiency testing surveys conducted by the College of American Pathologists between 2008 and 2018 were analyzed. The ANA titers reported for each specimen were ranked according to the kits being used by testing laboratories, and the statistical significance of the differences was determined.

RESULTS.—

The ANA titer results were strongly influenced by the HEp-2 ANA kit used (P < .001). During the 11 years studied, the rank order of the ANA titer for each kit relative to the other kits was remarkably consistent. The rank of ANA titer for individual ANA patterns observed for each kit was similar to the overall rank of that kit.

CONCLUSIONS.—

Variability in ANA titers was strongly associated with the kits used, and the differences between kits were quite consistent during the 11 years studied. Because the variability is not random, it has the potential to be managed by harmonizing kits, which could lead to improved consistency in reporting ANA titers.

Understanding and interpreting antinuclear antibody tests in systemic rheumatic diseases

Antinuclear antibodies (ANAs) are valuable laboratory markers to screen for and support the diagnosis of various rheumatic diseases (known as ANA-associated rheumatic diseases). The importance of ANA testing has been reinforced by the inclusion of ANA positivity as an entry criterion in the 2019 systemic lupus erythematosus classification criteria. In addition, specific ANAs (such as antibodies to Sm, double-stranded DNA (dsDNA), SSA/Ro60, U1RNP, topoisomerase I, centromere protein B (CENPB), RNA polymerase III and Jo1) are included in classification criteria for other rheumatic diseases. A number of techniques are available for detecting antibodies to a selection of clinically relevant antigens (such as indirect immunofluorescence and solid phase assays). In this Review, we discuss the advantages and limitations of these techniques, as well as the clinical relevance of the differences between the techniques, to provide guidance in understanding and interpreting ANA test results. Such understanding not only necessitates insight into the sensitivity and specificity of each assay, but also into the importance of the disease context and antibody level. We also highlight the value of titre-specific information (such as likelihood ratios).

New findings associated with presumptive systemic lupus erythematosus in a kitten

CASE SUMMARY

An 8-month-old neutered male domestic shorthair kitten was examined for anorexia, lethargy and palatine ulcers. Systemic lupus erythematosus (SLE) was suspected based on a positive antinuclear antibody (ANA) titer and six manifestations of autoimmunity: fever, paronychia, oral ulcers, proteinuria, thrombocytopenia and leukopenia. Mastocytemia was observed on the blood smear. Although the clinical presentation of this case meets the classification criteria for SLE in humans, tick-borne disease and histopathology evaluation of the oral and cutaneous lesions would have been necessary to support a definite diagnosis of SLE. Baseline ANA titration was performed in two laboratories with conflicting results, which may reflect substrate differences used for the titration, but a false-positive result cannot be excluded. The cat received prednisolone and all clinical and laboratory abnormalities resolved after two months of treatment. Subsequent ANA titers remained positive and were not correlated to the patient's clinical progression.

RELEVANCE AND NOVEL INFORMATION

This report describes new findings associated with a presumptive diagnosis of SLE in a kitten, highlighting that SLE may not be ruled out even in young cats and may be associated with mastocytemia. ANA titration is part of the initial diagnostic work-up of SLE but is a non-specific test and discrepancies can be observed between laboratories. The titration of more specific antibodies such as those used in humans would be helpful to diagnose SLE. ANA titration may not correlate with clinical activity of SLE; hence, the interest of an ANA titer follow-up to establish disease control warrants further investigation.

A new diagnostic algorithm for pattern-oriented autoantibody testing according to the ICAP nomenclature: A pilot study

The commercial tests currently available as second-level tests to detect ANA sub-specificities are generally used independently from the ANA immunofluorescence (IIF) pattern. The aim of this study was to evaluate the efficacy of the use of a customizable pattern-oriented antigenic panel by immunoblot (IB) using the International Consensus on ANA Patterns (ICAP) classification scheme, in order to introduce a novel and updated autoimmune diagnostic flowchart. 710 sera referred for routine ANA testing were selected on the basis of the ANA pattern according to the ICAP nomenclature (nuclear speckled AC-2,4,5; nucleolar AC-8,9,10,29; cytoplasmic speckled AC-18,19,20) and on an IIF titer ≥1:320. They were then assayed by three experimental IB assays using a panel of selected antigens. ICAP-oriented IB detected 515 antibody reactivities vs. 457 of traditional anti-ENA in the nuclear speckled pattern group, 108 vs. 28 in the nucleolar pattern group, and 43 vs. 34 in the cytoplasmic speckled pattern. This pilot study may lead the way for a new approach introducing an ICAP pattern-oriented follow up testing as a valid alternative to the existing standard panels, thus enabling more patients with autoimmune rheumatic disease to be accurately diagnosed.

Investigation and analysis of HEp 2 indirect immunofluorescence titers and patterns in various liver diseases

INTRODUCTION

Antinuclear antibody (ANA) testing using indirect immunofluorescence assay (IIFA) is a common and economical method which contributes to detect systemic autoimmune diseases (SARD) and autoimmune liver diseases (AILD). The primary aim of our study was to investigate ANA positivity and their patterns in multiple liver diseases, including primary biliary cirrhosis (PBC), autoimmune hepatitis (AIH), hepatitis B virus infection (HBV), hepatitis C virus infection (HCV), and hepatic carcinoma (HCC). Besides, we also compared the ANA titers and patterns in patients with liver disease, SARD, and healthy controls (HC).

METHODS

A total of 2537 patients with SARD, 137 PBC cases, 57 AIH cases, 3420 HBV cases, 769 HCV cases, 268 HCC cases, and 1073 HC were retrospectively assessed. The titers and patterns of ANA were detected with the IIFA method.

RESULTS

ANA positivity rate was considerably discernible between these diseases, which is 90.1% in SARD, 93.4% in PBC, 49.1% in AIH, 19.1% in HBV, 13.9% in HCV, and 23.5% in HCC. Moreover, only 4.9% of HCC cases, 2.5% of HBV patients, and 1.6% of HCV patients had an ANA titer ≥ 1:320. The mixed pattern which composed of at least two patterns majorly lied in PBC. AC-15 and AC-21 was frequently related to liver diseases; the former pattern was more frequently found in AIH (84.2%) and PBC (8.8%), and the latter pattern was easily seen in PBC (62.2%) and HCC (22.6%). The positive rate of ANA in HC was 12.2%, and its major pattern was AC-2.

CONCLUSIONS

There are differences in ANA positivity among patients with SARD and various liver diseases. Some mixed patterns may provide important evidence for the diagnosis of PBC. Clinicians should pay attention to ANA patterns and titer during the interpretation of this test. Key Points • Defining the clinical relevance of antinuclear antibody (ANA) using indirect immunofluorescence assay in the context of diseases can be an important tool for the clinician in the diagnostic work-up of patients with liver diseases. • The mixed pattern of ANA is majorly found in primary biliary cirrhosis (PBC). ANA patterns including AC-15 and AC-21 are frequently related to liver diseases. AC-15 is more often found in autoimmune hepatitis (AIH) (84.2%) and PBC (8.8%), and AC-21 is easily found in PBC (62.2%, and hepatic carcinoma (HCC) (22.6%). • ANA positivity can be seen in 19.1% of hepatitis B virus infection (HBV) cases, 13.9% of hepatitis C virus infection (HCV) cases, and 23.5% of HCC cases. Only 2.5% of HBV patients, 1.6% of HCV patients, and 4.9% of HCC cases have an ANA titer ≥ 1:320.

Idiopathic and immune-related pulmonary fibrosis: diagnostic and therapeutic challenges

Interstitial lung disease (ILD) encompasses a large group of pulmonary conditions sharing common clinical, radiological and histopathological features as a consequence of fibrosis of the lung interstitium. The majority of ILDs are idiopathic in nature with possible genetic predisposition, but is also well recognised as a complication of connective tissue disease or with certain environmental, occupational or drug exposures. In recent years, a concerted international effort has been made to standardise the diagnostic criteria in ILD subtypes, formalise multidisciplinary pathways and standardise treatment recommendations. In this review, we discuss some of the current challenges around ILD diagnostics, the role of serological testing, especially, in light of the new classification of Interstitial Pneumonia with Autoimmune Features (IPAF) and discuss the evidence for therapies targeted at idiopathic and immune-related pulmonary fibrosis.

V Brazilian consensus guidelines for detection of anti-cell autoantibodies on hep-2 cells

BACKGROUND

The V Brazilian Consensus for determination of autoantibodies against cellular constituents on HEp-2 cells, held in Brasilia (DF, Brazil) on August 27, 2016, discussed the harmonization between the Brazilian Consensus on ANA (BCA) guidelines and the International Consensus on ANA Patterns (ICAP) recommendations ( www.anapatterns.org ). Initial guidelines were formulated by the group of Brazilian experts with the purpose of guiding and enabling Brazilian clinical laboratories to adopt recommendations and to provide a common standard for national and international consensuses.

MAINBODY

Twenty Brazilian researchers and experts from universities and clinical laboratories representing the various geographical regions of the country participated in the meeting. Three main topics were discussed, namely the harmonization between the BCA guidelines and latest recommendations of the ICAP initiative, the adjustment of the terminology and report on HEp-2 patterns, and a reassessment of quality assurance parameters. For the three topics, our aim was to establish specific guidelines. All recommendations were based on consensus among participants. There was concrete progress in the adjustment of the BCA guidelines to match the ICAP guidelines. To a certain extent, this derives from the fact that ICAP recommendations were largely based on the algorithm and recommendations of the IV Brazilian ANA Consensus, as consistently recognized in the ICAP publications and presentations. However, although there is great overlap between the two Consensuses, there are some point divergences. These specific items were individually and extensively discussed, and it was acknowledged that in several points ICAP improved recommendations previously issued by the Brazilian ANA Consensus and these changes were readily implemented. Regarding some specific topics, the BCA panel of experts felt that the previously issued recommendations remained relevant and possibly will require further discussion with ICAP. The term anti-cell antibodies was adopted as the recommended designation, recognizing that the assay addresses antibodies against antigens in the nucleus and in other cell compartments. However, the acronym ANA HEp-2 was maintained due to historical and regulatory reasons. It was also signalized that the latest trend in ICAP is to adopt the term Indirect Immunofluorescent Assay on HEp-2 cell substrate (HEp-2 IIFA). In addition, the quality assurance strategies previously presented were ratified and emphasized.

CONCLUSION

The V BCA edition was successful in establishing an overall harmonization with the ICAP recommendations for interpretation of the HEp-2 IIFA test, pinpointing the perspectives in filling the remaining gaps between both initiatives.

A Multicenter Analysis of Subjectivity of Indirect Immunofluorescence Test in Antinuclear Antibody Screening

Objectives

This study aims to evaluate the interpretation of the antinuclear antibody (ANA)-indirect immunofluorescence (IIF) test results based on the interpreter-related subjectivity and to examine the inter-center agreement rates with the performance of each laboratory.

Patients and methods

The ANA-IIF testing was carried out in a total of 600 sera and evaluated by four laboratories. The inter-center agreement rates were detected. The same results given by the four centers were accepted as gold standard and the predictive values of each center were calculated.

Results

The inter-center agreement was reported for ANA-IIF test results from 392 of 600 (65.3%) sera, while 154 of 392 results were positive. Four study centers reported 213 (35.5%), 222 (37.0%), 266 (44.3%), and 361 (60.2%) positive test results, respectively. In terms of the patterns, the highest and lowest positive predictive values were 72.3% and 42.7%, respectively, while the highest and lowest negative predictive values were 99.6% and 61.5%, respectively. The agreement for semi-quantitative evaluation at three levels of fluorescence intensity stated by four centers was detected in 100 sera at 87% 3(+), while the other two levels were 6% and 7%. The highest predictive value for the highest fluorescence intensity of 3(+) was found to be 71.9%.

Conclusion

Significant differences may be observed among laboratories in terms of qualitative results, patterns, and semi-quantitative determination of the fluorescence intensity in the ANA-IIF testing, particularly at low fluorescence intensity levels and in those with speckled patterns. In case of any discrepancy between ANA-IIF test and clinical prediagnosis, the test should be repeated in another laboratory, if necessary.

Clinical relevance of HEp-2 indirect immunofluorescent patterns: the International Consensus on ANA patterns (ICAP) perspective

The indirect immunofluorescence assay (IIFA) on HEp-2 cells is widely used for detection of antinuclear antibodies (ANA). The dichotomous outcome, negative or positive, is integrated in diagnostic and classification criteria for several systemic autoimmune diseases. However, the HEp-2 IIFA test has much more to offer: besides the titre or fluorescence intensity, it also provides fluorescence pattern(s). The latter include the nucleus and the cytoplasm of interphase cells as well as patterns associated with mitotic cells. The International Consensus on ANA Patterns (ICAP) initiative has previously reached consensus on the nomenclature and definitions of HEp-2 IIFA patterns. In the current paper, the ICAP consensus is presented on the clinical relevance of the 29 distinct HEp-2 IIFA patterns. This clinical relevance is primarily defined within the context of the suspected disease and includes recommendations for follow-up testing. The discussion includes how this information may benefit the clinicians in daily practice and how the knowledge can be used to further improve diagnostic and classification criteria.

A computer-aided diagnosis system for HEp-2 fluorescence intensity classification

BACKGROUND AND OBJECTIVE

The indirect immunofluorescence (IIF) on HEp-2 cells is the recommended technique for the detection of antinuclear antibodies. However, it is burdened by some limitations, as it is time consuming and subjective, and it requires trained personnel. In other fields the adoption of deep neural networks has provided an effective high-level abstraction of the raw data, resulting in the ability to automatically generate optimized high-level features.

METHODS

To alleviate IIF limitations, this paper presents a computer-aided diagnosis (CAD) system classifying HEp-2 fluorescence intensity: it represents each image using an Invariant Scattering Convolutional Network (Scatnet), which is locally translation invariant and stable to deformations, a characteristic useful in case of HEp-2 samples. To cope with the inter-observer discrepancies found in the dataset, we also introduce a method for gold standard computation that assigns a label and a reliability score to each HEp-2 sample on the basis of annotations provided by expert physicians. Features by Scatnet and gold standard information are then used to train a Support Vector Machine.

RESULTS

The proposed CAD is tested on a new dataset of 1771 images annotated by three independent medical centers. The performances achieved by our CAD in recognizing positive, weak positive and negative samples are also compared against those obtained by other two approaches presented so far in the literature. The same system trained on this new dataset is then tested on two public datasets, namely MIVIA and I3Asel.

CONCLUSIONS

The results confirm the effectiveness of our proposal, also revealing that it achieves the same performance as medical experts.

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

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

The inter-observer reading variability in anti-nuclear antibodies indirect (ANA) immunofluorescence test: A multicenter evaluation and a review of the literature

Recently there has been an increase demand for Computer-Aided Diagnosis (CAD) tools to support clinicians in the field of Indirect ImmunoFluorescence (IIF), as the novel digital imaging reading approach can help to overcome the reader subjectivity. Nevertheless, a large multicenter evaluation of the inter-observer reading variability in this field is still missing. This work fills this gap as we evaluated 556 consecutive samples, for a total of 1679 images, collected in three laboratories with IIF expertise using HEp-2 cell substrate (MBL) at 1:80 screening dilution according to conventional procedures. In each laboratory, the images were blindly classified by two experts into three intensity classes: positive, negative, and weak positive. Positive and weak positive ANA-IIF results were categorized by the predominant fluorescence pattern among six main classes. Data were pairwise analyzed and the inter-observer reading variability was measured by Cohen's kappa test, revealing a pairwise agreement little further away than substantial both for fluorescence intensity and for staining pattern recognition (k=0.602 and k=0.627, respectively). We also noticed that the inter-observer reading variability decreases when it is measured with respect to a gold standard classification computed on the basis of labels assigned by the three laboratories. These data show that laboratory agreement improves using digital images and comparing each single human evaluation to potential reference data, suggesting that a solid gold standard is essential to properly make use of CAD systems in routine work lab.

Automated antinuclear immunofluorescence antibody analysis is a reliable approach in routine clinical laboratories

Background:

Indirect immunofluorescence (IIF) assays are recommended as the gold standard method for the detection of antinuclear antibodies (ANAs). This study aimed to investigate the reliability of an automated system.

Methods:

We compared 3745 serum samples using NOVA View archived images with manual analysis via microscopy. A custom cutoff value was established to distinguish ANA titers and was validated in two clinical laboratories. The automatic ANA pattern recognition system was evaluated, and all ANA-positive sera were subjected to two commercial ANA IIF kits to compare the consistency of the pattern interpretation results. For inconsistent patterns, a third ANA IIF testing kit was utilized.

Results:

Agreement of the interpretation of the ANA IIF test using the platform of NOVA View and manual microscopy was 96.9%. The local cutoff value to discriminate ANA titers in four main ANA patterns was calculated based on 1390 serum samples. In our laboratory, the titer prediction accuracy was superior to the preset cutoff in NOVA View (p<0.01); the performance was similar in another laboratory (p=0.11). The automatic pattern recognition accuracies of speckled, homogeneous, centromere, nucleolar and nuclear dot patterns were 62.7%, 57.4%, 92.6%, 30.5% and 27.3%, respectively. The consistency of the pattern interpretation results between INOVA and MBL kits was 95.3%.

Conclusions:

It is necessary to establish a custom value-added ANA report. However, confirmation of the digital immunofluorescence images by expert technicians was essential, and suspect results of an ANA pattern should be reconfirmed by another commercial ANA IIF kit to achieve more reliable results.

Automated indirect immunofluorescence microscopy enables the implementation of a quantitative internal quality control system for anti-nuclear antibody (ANA) analysis

BACKGROUND

Screening for anti-nuclear antibodies by indirect immunofluorescence (ANA-IIF) remains mandatory in the serological work-up of connective tissue diseases. Recently, automated approaches were introduced that may improve harmonization. Here, we investigated whether the introduction of automated ANA-IIF and more specifically the use of its quantitative measure, could improve ANA-IIF internal quality control (IQC) management.

METHODS

We retrospectively reviewed results of two cohorts of routine samples and parallel IQC data collected from January 2010 to February 2013 and from February to mid October 2013. For the first cohort, data were collected using conventional microscopy. The second cohort was analyzed by an automated ANA-IIF microscope (Zenit G sight, A. Menarini). Retrospectively, we evaluated the applicability of the probability index (PI) of control material measurements and patient results for IQC management based on Westgard multirules. This approach was also compared with monthly monitoring of the %ANA-IIF positive samples.

RESULTS

In our historical data set, we showed that monitoring of %ANA positives identified systematic errors that were not detected by monitoring control material results. Data resulting from automated microscopy showed that PI measurements on control material remained stable within the observed period and that Westgard multirules can be used for IQC follow-up. Parallel monitoring of the daily median patient PI and the monthly %ANA positives, showed that the daily median was a sensitive and fast tool for detecting systematic errors.

CONCLUSIONS

The introduction of the automated ANA-IIF microscope could enable objective IQC procedures and should be considered an important step forward in ANA-IIF harmonization.

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.

Novel method for ANA quantitation using IIF imaging system

A variety of antinuclear antibodies (ANAs) are found in the serum of patients with autoimmune diseases. The detection of abnormal ANA titers is a critical criterion for diagnosis of systemic lupus erythematosus (SLE) and other connective tissue diseases. Indirect immunofluorescence assay (IIF) on HEp-2 cells is the gold standard method to determine the presence of ANA and therefore provides information about the localization of autoantigens that are useful for diagnosis. However, its utility was limited in prognosing and monitoring of disease activity due to the lack of standardization in performing the technique, subjectivity in interpreting the results and the fact that it is only semi-quantitative. On the other hand, ELISA for the detection of ANA can quantitate ANA but could not provide further information about the localization of the autoantigens. It would be ideal to integrate both of the quantitative and qualitative methods. To address this issue, this study was conducted to quantitatively detect ANAs by using IIF imaging analysis system. Serum samples from patients with ANA positive (including speckled, homogeneous, nuclear mixture and cytoplasmic mixture patterns) and negative were detected for ANA titers by the classical IIF and analyzed by an image system, the image of each sample was acquired by the digital imaging system and the green fluorescence intensity was quantified by the Image-Pro plus software. A good correlation was found in between two methods and the correlation coefficients (R(2)) of various ANA patterns were 0.942 (speckled), 0.942 (homogeneous), 0.923 (nuclear mixture) and 0.760 (cytoplasmic mixture), respectively. The fluorescence density was linearly correlated with the log of ANA titers in various ANA patterns (R(2)>0.95). Moreover, the novel ANA quantitation method showed good reproducibility (F=0.091, p>0.05) with mean±SD and CV% of positive, and negative quality controls were equal to 126.4±9.6 and 7.6%, 10.4±1.25 and 12.0%, respectively. In conclusion, our novel ANA quantitation method can provide both of the fluorescence density, which could precisely reflect the fluctuate of ANAs level in patient's serum and the useful information about the localization of the autoantigens for clinician in diagnosing and monitoring diseases.

A decision support system for Crithidia luciliae image classification

OBJECTIVE

Systemic lupus erythematosus is a connective tissue disease affecting multiple organ systems and characterised by a chronic inflammatory process. It is considered a very serious sickness, further to be classified as an invalidating chronic disease. The recommended method for its detection is the indirect immunofluorescence (IIF) based on Crithidia Luciliae (CL) substrate. Hoverer, IIF is affected by several issues limiting tests reliability and reproducibility. Hence, an evident medical demand is the development of computer-aided diagnosis tools that can offer a support to physician decision.

METHODS

In this paper we propose a system that classifies CL wells integrating information extracted from different images. It is based on three main decision phases. Two steps, named as threshold-based classification and single cells recognition, are applied for image classification. They minimise false negative and false positive classifications, respectively. Feature extraction and selection have been carried out to determine a compact set of descriptors to distinguish between positive and negative cells. The third step applies majority voting rule at well recognition level, enabling us to recover possible errors provided by previous phases.

RESULTS

The system performance have been evaluated on an annotated database of IIF CL wells, composed of 63 wells for a total of 342 images and 1487 cells. Accuracy, sensitivity and specificity of image recognition step are 99.4%, 98.6% and 99.6%, respectively. At level of well recognition, accuracy, sensitivity and specificity are 98.4%, 93.3% and 100.0%, respectively. The system has been also validated in a daily routine fashion on 48 consecutive analyses of hospital outpatients and inpatients. The results show very good performance for well recognition (100% of accuracy, sensitivity and specificity), due to the integration of cells and images information.

CONCLUSIONS

The described recognition system can be applied in daily routine in order to improve the reliability, standardisation and reproducibility of CL readings in IIF.

Novel method for quantitative ANA measurement using near-infrared imaging

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

Indirect immunofluorescence in autoimmune diseases: Assessment of digital images for diagnostic purpose

BACKGROUND

The recommended method for antinuclear antibodies (ANA) detection is indirect immunofluorescence (IIF). To pursue a high image quality without artefacts and reduce interobserver variability, this study aims at evaluating the reliability of automatically acquired digital images of IIF slides for diagnostic purposes.

METHODS

Ninety-six sera were screened for ANA by IIF on HEp-2 cells. Two expert physicians looking at both the fluorescence microscope and the digital images on computer monitor performed a blind study to evaluate fluorescence intensity and staining pattern. Cohen's kappa was used as an agreement evaluator between methods and experts.

RESULTS

Considering fluorescence intensity, there is a substantial agreement between microscope and monitor analysis in both physicians. Agreement between physicians was substantial at the microscope and perfect at the monitor. Considering IIF pattern, there was a substantial and moderate agreement between microscope and monitor analysis in both physicians. Kappa between physicians was substantial both at the microscope and at the monitor.

CONCLUSIONS

These preliminary results suggest that digital media is a reliable tool to help physicians in detecting autoantibodies in IIF. Our data represent a first step to validate the use of digital images, thus offering an opportunity for standardizing and automatizing the detection of ANA by IIF.