Accreditation in autoimmune diagnostic laboratories. A position paper of the European Autoimmunity Standardisation Initiative (EASI)

Evolution of autoimmune diagnostics over the past 10 years: lessons learned from the UK NEQAS external quality assessment EQA programs

OBJECTIVES

External quality assessment (EQA) programs play a pivotal role in harmonizing laboratory practices, offering users a benchmark system to evaluate their own performance and identify areas requiring improvement. The objective of this study was to go through and analyze the UK NEQAS "Immunology, Immunochemistry and Allergy" EQA reports between 2012 and 2021 to assess the overall level of harmonization in autoimmune diagnostics and identify areas requiring improvement for future actions.

METHODS

The EQA programs reviewed included anti-nuclear (ANA), anti-dsDNA, anti-centromere, anti-extractable nuclear antigen (ENA), anti-phospholipids, anti-neutrophil cytoplasm (ANCA), anti-proteinase 3 (PR3), anti-myeloperoxidase (MPO), anti-glomerular basement membrane (GBM), rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA), mitochondrial (AMA), liver-kidney-microsomal (LKM), smooth muscle (ASMA), APCA, and celiac disease antibodies.

RESULTS

In the analyzed period, the number in participating laboratories showed an increase for almost all programs. Among solid phase methods, the use of ELISA techniques showed a progressive reduction, while new technologies, such as the fluoroenzymatic immunoassay, chemiluminescence immunoassay, Luminex and immunoblot showed an increased number of users. The number of results complying with the expected negative or positive target slightly increased for almost all antibodies in the last decade. A description of the most frequent causes of mistakes or misinterpretation for each specific test and method is also provided in this study.

CONCLUSIONS

Although numerous challenges need to be addressed in the area of autoantibody detection to enhance testing quality and attain higher harmonization, the period analyzed revealed that the ever-expanding range of autoantibodies, coupled with the introduction of new tests and methodologies and the advent of automated platforms, has brought about significant changes in autoimmune diagnostics.

Harmonization of ANA testing challenge: quantification strategy to accurately predict end-point titers avoiding serial dilution

Despite the advantages of automated systems for antinuclear antibody (ANA) analysis, the prediction of end-point titers avoiding serial dilutions is still in progress. The aims of this study were to set a conversion table providing discriminant ranges of fluorescence signal intensity values (FI) corresponding to the end-point titers and validate this tool in a real-life laboratory setting. Eight hundred ninety-four serum samples were analyzed for ANA using Image Navigator System. In order to classify FI into non-overlapping groups corresponding to conventional end-point titers, statistical discriminant analysis was used. Validation study was performed calculating agreement and error rates between visual readings and conversion table of 1119 routine ANA positive samples. Setting of FI ranges corresponding to the end-point titers for different staining patterns was computed. For samples showing single pattern, the overall agreement between visual readings and conversion table was 98.4% for all titers ranging from 1:160 to 1:2560, of which 68.0% had the same titer and 30.4% were within ± one titer difference. Concordance rates according to ANA patterns were as follows: (1) nuclear 98.4%, of which 67.0% had the same titer and 31.4% ± one titer; (2) cytoplasmic 100%, of which 72.7% had the same titer and 27.3% than ± one titer; (3) mitotic 66.6%, of which 33.3% had more ± one titer. Our study developed a quantification method for autoantibodies titers assessment based on just one single sample dilution instead of traditional serial dilution approach, providing significant advantages in routine laboratory in terms of reduction in hand-on time and harmonization of results.

Dyspepsia-Like Symptoms in Helicobacter pylori-Negative Chronic Gastritis are Associated with ASCA-, ANCA-, and Celiac Seropositivity but Not with Other Autoimmune Parameters: A Single-Centre, Retrospective Cross-Sectional Study

Introduction

Dyspeptic symptoms are frequent in the general population, with a high socioeconomic burden. Helicobacter pylori (H. pylori) might be a possible etiological factor; however, it is also common in H. pylori negative gastritis. Clarification of the underlying aetiology might be beneficial to set up the optimal treatment strategy for dyspepsia and chronic gastritis (CG) itself. We aimed to assess the prevalence of dyspeptic symptoms in patients with H. pylori negative CG and explore autoimmunity's possible role.

Methods

This retrospective study included data from patients with H. pylori negative CG. Exclusion criteria were (1) acute gastritis; (2) reactive gastropathy; (3) subjects without any serology testing results; (4) H. pylori positivity; (5) presence of atrophy, intestinal metaplasia (IM), gastroesophageal reflux disease (GERD), ulcer, or cancer. The following endpoints were assessed (1) the rate of dyspepsia-like symptoms; (2) association between dyspepsia and autoimmune disease-related seromarker positivity (AISP); (3) frequency of other symptoms in CG and its association with AISP; (4) location of the inflammation and its association with AISP.

Results

From a total of 285 patients, 175 were included in this study. Among these patients, 95 experienced dyspeptic symptoms (54.29%) and were associated more with AISP (p = 0.012), especially with celiac seropositivity (p = 0.045), anti-neutrophil cytoplasmic antibody (ANCA) and anti-Saccharomyces cerevisiae antibodies (ASCA) positivity (p = 0.043). A significant association was not found with other tested autoimmune (AI)-related antibody positivity.

Conclusion

Positivity of seromarkers of autoimmune diseases in chronic gastritis may predispose to have dyspeptic symptoms and may be the causative factor behind some cases of uninvestigated dyspepsia. These data suggest that further prospective studies are needed to clarify whether screening for autoantibodies in patients with dyspepsia is cost-effective and helps the earlier diagnosis of autoimmune diseases.

Repository of intra- and inter-run variations of quantitative autoantibody assays: a European multicenter study

OBJECTIVES

No reference data are available on repositories to measure precision of autoantibody assays. The scope of this study was to document inter- and intra-run variations of quantitative autoantibody assays based on a real-world large international data set.

METHODS

Members of the European Autoimmunity Standardisation Initiative (EASI) group collected the data of intra- and inter-run variability obtained with assays quantifying 15 different autoantibodies in voluntary participating laboratories from their country. We analyzed the impact on the assay performances of the type of immunoassay, the number of measurements used to calculate the coefficient of variation (CVs), the nature and the autoantibody level of the internal quality control (IQC).

RESULTS

Data were obtained from 64 laboratories from 15 European countries between February and October 2021. We analyzed 686 and 1,331 values of intra- and inter-run CVs, respectively. Both CVs were significantly dependent on: the method of immunoassay, the level of IQC with higher imprecision observed when the antibody levels were lower than 2-fold the threshold for positivity, and the nature of the IQC with commercial IQCs having lower CVs than patients-derived IQCs. Our analyses also show that the type of autoantibody has low impact on the assay' performances and that 15 measurements are sufficient to establish reliable intra- and inter-run variations.

CONCLUSIONS

This study provides for the first time an international repository yielding values of intra- and inter-run variation for quantitative autoantibody assays. These data could be useful for ISO 15189 accreditation requirements and will allow clinical diagnostic laboratories to assure quality of patient results.

ANCA Testing in Clinical Practice: From Implementation to Quality Control and Harmonization

Analyses for the presence of anti-neutrophil cytoplasmic antibodies (ANCA) are important in the diagnostic work-up of patients with small vessel vasculitis. Since current immuno-assays are predominantly designed for diagnosis of patients with ANCA-associated vasculitis (AAV), implementation in routine clinical practice, internal and external quality control, and harmonization are focused on this particular use. However, ANCA testing may also be relevant for monitoring therapy efficacy and for predicting a clinical relapse in AAV patients, and even for diagnostic purposes in other clinical situations. In the current review, the topics of implementation, quality control, and standardization vs. harmonization are discussed while taking into account the different applications of the ANCA assays in the context of AAV.

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.

Integrating quality assurance in autoimmunity: the changing face of the automated ANA IIF test

OBJECTIVES

Currently available computer-aided diagnosis (CAD) systems for the detection of anti-nuclear antibodies (ANA) by indirect immunofluorescence (IIF) assay enable a standardized measurement of system-specific fluorescent intensity (FI) measures. We aimed to evaluate an internal quality control (iQC) program that controls the total ANA IIF process in routine practice.

METHODS

In addition to the kit iQC materials, supplemental quality indicators were integrated in a total quality assurance (QA) program: patient-derived iQC's samples (negative, 1/160 fine speckled and 1/160 homogeneous), median sample FI per run and percentage of ANA IIF positive samples per run. Analytical rejection criteria were based on the imprecision of the positivity index (PI) measure of the Zenit PRO system (Menarini). Clinical rejection criteria were based on changes in FI that correspond to a change in ANA IIF titer of ≥2. To evaluate the QA program, different artificial errors were introduced during the ANA IIF process. After every run, quality indicators were evaluated and compared to the pre-set target values.

RESULTS

Rescanning the ANA IIF slides five times, using an old conjugate and a needle obstruction resulted in analytically and even clinically relevant errors in ANA IIF results. All errors were correctly detected by the different defined quality indicators. Traditional Westgard rules, including analytically (and clinically) defined rejection limits were useful in monitoring quality indicators.

CONCLUSIONS

The integration of a total process iQC program in CAD systems, based on the specific FI measurands and performance criteria of the system, adds value to QA.

Quality and best practice in medical laboratories: specific requests for autoimmunity testing

Special conditions associated with laboratory autoimmune testing are not well compatible with recent developments in regulatory frameworks such as EN/ISO 15189 accreditation or in vitro diagnostic medical device regulation (IVD-R). In addition, international recommendations, guidelines and disease criteria are poorly defined with respect to requirements on autoantibody testing. Laboratory specialists from Austria, Belgium, Croatia, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Norway, Poland, Portugal, South Africa, Spain, Sweden, Switzerland, and The Netherlands collected information, reported national experience, and identified quality issues in relation to autoantibody testing that require consensus on interpretation of the regulatory frameworks and guidelines. This process has been organized by the European Autoimmunity Standardisation Initiative (EASI). By identifying the critical items and looking for a consensus, our objective was to define a framework for, in particular, EN/ISO accreditation purposes. Here, we present a review of current publications and guidelines in this field to unify national guidelines and deliver in this way a European handout on quality control and accreditation for laboratories involved in autoantibody testing. We focus on quality items that can be checked during accreditation visits. Despite various local varieties, we encountered an overwhelming dedication to quality assurance in all contributing countries.

Precision of autoantibody assays in clinical diagnostic laboratories: What is the reality?

BACKGROUND

ISO 15189 accreditation remains a challenge for specialized laboratories. In the field of autoimmunity, beside the crucial problem of absence of standardization, laboratories have to manage the analytical performances of the large panel of assays in terms of sensitivity and specificity, but also on their measurement precision for which no reference values are available on biorepositories.

METHODS

As an initiative of the French EASI (European Autoimmunity Standardization Initiative) group, French clinical diagnostic laboratories were requested to participate in a survey aiming to analyze the coefficients of variation (CVs) of intra-run and inter-run variability obtained with assays quantifying 14 different autoantibodies. Two performance goals corresponding to the 90th percentile and the 50th percentile (lowest CV values reached by 90% and 50% of laboratories respectively) defined for three levels of concentration were calculated. The impact on the assay performances of the number of measurements, of the nature of the internal quality control (IQC) and the type of immunoassay, was also analyzed.

RESULTS

414 and 616 values of intra-run and inter-run CVs were collected, respectively. The 50th percentile performance goals were comprised between 1.0% and 8.9% for the intra-run CVs, and between 1.8% and 14.6% for the inter-run CVs. At 90th percentile, the performance goals were comprised between 3.2% and 13.5% for the intra-run CVs, and between 7.3% and 30.8% for the inter-run CVs. CVs calculated from 10 values were similar to those obtained from more values. Higher imprecision was observed when the antibody levels of the IQC was lower than 2 fold the positive threshold. Commercial IQCs gave lower CVs than IQCs derived from patient samples.

CONCLUSION

Our results allow proposing some acceptability limits for the precision performances of the autoantibody assays, compatible with the reality of life in diagnostic laboratories and clinical care.

Serology-based criteria for adult coeliac disease have excellent accuracy across the range of pre-test probabilities

BACKGROUND

The revised paediatric criteria for coeliac disease allow omission of duodenal biopsies in symptomatic children who have specific serology and coeliac disease-associated genetics. It remains unclear whether this approach is also applicable for adults with various clinical presentations.

AIM

To evaluate the accuracy of serology-based criteria in adults with variable pre-test probabilities for coeliac disease.

METHODS

Three study cohorts comprised adults with high-risk clinical coeliac disease suspicion (n = 421), moderate-risk family members of coeliac disease patients (n = 2357), and low-risk subjects from the general population (n = 2722). Serological and clinical data were collected, and "triple criteria" for coeliac disease comprised transglutaminase 2 antibodies >10× the upper limit of normal, positive endomysium antibodies, and appropriate genetics without requirement of symptoms. The diagnosis was based on intestinal biopsy.

RESULTS

The diagnosis of coeliac disease was established in 274 subjects. Of these, 59 high-risk subjects, 17 moderate-risk subjects, and 14 low-risk subjects fulfilled the "triple criteria". All had histologically proven coeliac disease, giving the criteria a positive predictive value of 100%. Altogether, 90 (33%) of all 274 newly diagnosed patients could have avoided biopsy, including 37% among high-risk, 20% among moderate-risk, and 48% among low-risk patients. No histological findings other than coeliac disease were found in the biopsies of "triple positive" subjects.

CONCLUSIONS

Coeliac disease can reliably and safely be diagnosed without biopsy in adults fulfilling the "triple criteria" regardless of the pre-test probability. Revised criteria would enable the number of endoscopies to be reduced by one-third.

Detection of Anti-neutrophil Cytoplasmic Antibodies (ANCA) by Indirect Immunofluorescence

The eventual presence of anti-neutrophil cytoplasmic antibodies (ANCA) can initially be screened with indirect immunofluorescence (IIF). The majority of laboratories that facilitate ANCA testing use commercial kits. Although in-house assays are not encouraged in routine clinical laboratories, knowledge on the methodological aspects of the assay remains of importance. These aspects include choice of substrate, choice of fixative, staining procedure, and interpretation procedure. In this paper details on the methodology are provided and discussed in the context of the clinical application.

Validation conform ISO-15189 of assays in the field of autoimmunity: Joint efforts in The Netherlands

ISO 15189:2012 requires validation of methods used in the medical laboratory, and lists a series of performance parameters for consideration to include. Although these performance parameters are feasible for clinical chemistry analytes, application in the validation of autoimmunity tests is a challenge. Lack of gold standards or reference methods in combination with the scarcity of well-defined diagnostic samples of patients with rare diseases make validation of new assays difficult. The present manuscript describes the initiative of Dutch medical immunology laboratory specialists to combine efforts and perform multi-center validation studies of new assays in the field of autoimmunity. Validation data and reports are made available to interested Dutch laboratory specialists.

EASI – European Autoimmunity Standardisation Initiative: facing the challenges of diagnostics in autoimmunity

The European Autoimmunity Standardisation Initiative (EASI) has been founded in order to improve autoimmune diagnostics by stimulating the interaction between the clinicians and laboratory specialists, by standardization of autoantibody tests, and by harmonization of testing algorithms. The ultimate goal of EASI is to utilize autoimmune diagnostics in the best way in order to optimize patient care. This mini-review gives an overview of the historical perspective of EASI and summarizes the major achievements.