Evaluation of a New Multiparametric Microdot Array-Based Immunoassay Panel for Systemic Autoimmune Disease Diagnosis

BACKGROUND

The early reliable detection and quantification of autoantibodies play an important role in autoimmune disease diagnosis and in disease-course monitoring. New technologies, such as the multiplexed determination of autoantibodies, have recently been introduced and are being adopted more frequently. The aim of this study was to evaluate the ability of a new microdot array-based multiparametric assay (ZENIT AMiDot CTD panel, A. Menarini Diagnostics, Firenze, Italy) to correctly classify patients with autoimmune rheumatic diseases (ARDs) and compare it to a fluorescence enzyme immunoassay (FEIA) for the detection of anti-ENAs.

METHODS

The study included 69 consecutive samples from patients with ARDs that were analyzed using two different methods (FEIA and AMiDot) to detect anti-CENP B and six anti-ENA antibodies: anti-Scl-70, anti-SSB/La, anti-Jo-1, anti-U1-RNP, anti-Ro52, and anti-Ro60. The control group sera came from sixty-eight blood donors. Tests were run on the automated slide processor ZENIT FLOW, and then the slides were imaged and analyzed using ZENIT fast.

RESULTS

Since the samples were selected for at least one antibody positivity with an ARD diagnosis, we did not calculate clinical sensitivity but only specificity, which was 98.53%, ranging from 90% for anti-SSB/La antibodies to 100% for anti-CENP B ones. Mean agreement among the methods assessed by Cohen's kappa was 0.816 ± 0.240.

CONCLUSIONS

The assay demonstrated good clinical performance and may be considered a valuable aid in detecting ARD patients, offering an alternative to methods such as FEIA which are largely in use today.

Analytical and clinical performance of different platforms simultaneously detecting 15 antinuclear antibodies

Background

Antinuclear antibodies (ANAs) are invaluable biomarkers for the diagnosis of autoimmune diseases (AIDs). This study aims to compare the performances of line immunoassay (LIA), multiplex bead‐based flow fluorescent immunoassay (MBFFI), and magnetic bar code immunofluorescence assay (MBC‐IF) to detect ANA‐Profile‐15S.

Methods

In total, 184 samples from AID patients and 50 healthy controls (HCs) were collected. Fifteen ANAs (anti‐dsDNA, nucleosome, histone, Sm, PCNA, ribosomal‐P, SS‐A/Ro52, SS‐A/Ro60, SS‐B/La, centromere B [CENP‐B], Scl‐70, U1‐snRNP, AMA‐M2, Jo‐1, and Pm/Scl) were subjected to parallel detection by the LIA, MBFFI, and MBC‐IF. The consistency between assays was analyzed. The discrepant results were further examined by chemiluminescent immunoassay (CLIA).

Results

Anti‐SS‐A/Ro52 and SS‐A/Ro60 autoantibodies were the most common autoantibodies in ANA positive‐profiles, and were detected with equal efficiency by the LIA, MBFFI, and MBC‐IF (p = 0.101 and p = 0.732, respectively). The three assays showed excellent agreement (consistency range: 66.5%–97.5%), and total consistency was 85.8%. The MBFFI and MBC‐IF assays were in good agreement in terms of ANA‐Profile‐15S determination; the kappa coefficient ranged from 0.59 to 0.95, except for the PCNA and PM‐Scl. Of the 262 re‐assessed divergent results, 124 (47.33%) were positive on CLIA; the various autoantibodies exhibited variable patterns. More importantly, the ANA‐Profile‐15S results of the MBFFI and MBC‐IF accurately identified patients with AID; the area under the curves ranged from 0.642 to 0.919.

Conclusions

The novel MBFFI and MBC‐IF assay performed well in detecting ANA‐Profile‐15S. The application of MBFFI and MBC‐IF play important roles in laboratory diagnosis of AIDs.

Laboratory evaluation of anti-dsDNA antibodies

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