Inova Diagnostics Research Articles

Comparison of the analytical and clinical performances of four anti-cyclic citrullinated peptide antibody assays for diagnosing rheumatoid arthritis.

Anti-cyclic citrullinated peptide antibody (anti-CCP) is one of the most important serologic markers for diagnosing rheumatoid arthritis (RA). This study aimed to compare the analytical and clinical performances of the second- and third-generation anti-CCP assays. Four automated anti-CCP assays were evaluated: Chorus anti-CCP (Diesse Diagnostica), Elecsys anti-CCP (Roche Diagnostics), Atellica® IM anti-CCP IgG (Siemens Healthineers), and Quanta Flash® CCP3 (Inova Diagnostics Inc.). Analytical performance included the precision, linearity, correlation, and concordance rate. For evaluating the clinical performance, 240 patient samples (120 positive and 120 negative samples, determined by the Chorus anti-CCP assay) were used, including those with a diagnosis of RA (n = 132) and non-RA (n = 108). Using receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity were evaluated. All four assays that were evaluated showed good precision and linearity, and their correlation and concordance rates were in acceptable ranges. The area under the curve (AUC) values ranged from 0.888 to 0.914, showing a good diagnostic performance. The sensitivity and specificity of all assays were similar (88.0-97.2%). All four anti-CCP assays showed good analytical and diagnostic performances for diagnosing RA. After adjusting the cutoff values, these assays are expected to show enhanced sensitivity and specificity. Key Points • Previous studies have described the diagnostic performance of a few immunologic markers in RA diagnosis, but nothing has been proven to be sufficiently good in clinical practice. • All four automated anti-CCP assays showed good analytical and diagnostic performances for diagnosing RA in clinical practice. • After adjusting the cutoff values, these assays are expected to show enhanced sensitivity and specificity. • The present study provides reassuring evidence that any of the studied commercially available anti-CCP tests for detecting rheumatoid arthritis provide similar diagnostic information to institutions that adopt these specific testing systems.

Golgi protein-73: A biomarker for assessing cirrhosis and prognosis of liver disease patients.

BACKGROUNDReliable biomarkers of cirrhosis, hepatocellular carcinoma (HCC), or progression of chronic liver diseases are missing. In this context, Golgi protein-73 (GP73) also called Golgi phosphoprotein-2, was originally defined as a resident Golgi type II transmembrane protein expressed in epithelial cells. As a result, GP73 expression was found primarily in biliary epithelial cells, with only slight detection in hepatocytes. However, in patients with acute or chronic liver diseases and especially in HCC, the expression of GP73 is significantly up-regulated in hepatocytes. So far, few studies have assessed GP73 as a diagnostic or prognostic marker of liver fibrosis and disease progression.AIMTo assess serum GP73 efficacy as a diagnostic marker of cirrhosis and/or HCC or as predictor of liver disease progression.METHODSGP73 serum levels were retrospectively determined by a novel GP73 ELISA (QUANTA Lite® GP73, Inova Diagnostics, Inc., Research Use Only) in a large cohort of 632 consecutive patients with chronic viral and non-viral liver diseases collected from two tertiary Academic centers in Larissa, Greece (n = 366) and Debrecen, Hungary (n = 266). Aspartate aminotransferase (AST)/Platelets (PLT) ratio index (APRI) was also calculated at the relevant time points in all patients. Two hundred and three patients had chronic hepatitis B, 183 chronic hepatitis C, 198 alcoholic liver disease, 28 autoimmune cholestatic liver diseases, 15 autoimmune hepatitis, and 5 with other liver-related disorders. The duration of follow-up was 50 (57) mo [median (interquartile range)]. The development of cirrhosis, liver decompensation and/or HCC during follow-up were assessed according to internationally accepted guidelines. In particular, the surveillance for the development of HCC was performed regularly with ultrasound imaging and alpha-fetoprotein (AFP) determination every 6 mo in cirrhotic and every 12 mo in non-cirrhotic patients.RESULTSIncreased serum levels of GP73 (> 20 units) were detected at initial evaluation in 277 out of 632 patients (43.8%). GP73-seropositivity correlated at baseline with the presence of cirrhosis (96.4% vs 51.5%, P < 0.001), decompensation of cirrhosis (60.3% vs 35.5%, P < 0.001), presence of HCC (18.4% vs 7.9%, P < 0.001) and advanced HCC stage (52.9% vs 14.8%, P = 0.002). GP73 had higher diagnostic accuracy for the presence of cirrhosis compared to APRI score [Area under the curve (AUC) (95%CI): 0.909 (0.885-0.934) vs 0.849 (0.813-0.886), P = 0.003]. Combination of GP73 with APRI improved further the accuracy (AUC: 0.925) compared to GP73 (AUC: 0.909, P = 0.005) or APRI alone (AUC: 0.849, P < 0.001). GP73 levels were significantly higher in HCC patients compared to non-HCC [22.5 (29.2) vs 16 (20.3) units, P < 0.001) and positively associated with BCLC stage [stage 0: 13.9 (10.8); stage A: 17.1 (16.8); stage B: 19.6 (22.3); stage C: 32.2 (30.8); stage D: 45.3 (86.6) units, P < 0.001] and tumor dimensions [very early: 13.9 (10.8); intermediate: 19.6 (18.4); advanced: 29.1 (33.6) units, P = 0.004]. However, the discriminative ability for HCC diagnosis was relatively low [AUC (95%CI): 0.623 (0.570-0.675)]. Kaplan-Meier analysis showed that the detection of GP73 in patients with compensated cirrhosis at baseline, was prognostic of higher rates of decompensation (P = 0.036), HCC development (P = 0.08), and liver-related deaths (P < 0.001) during follow-up.CONCLUSIONGP73 alone appears efficient for detecting cirrhosis and superior to APRI determination. In combination with APRI, its diagnostic performance can be further improved. Most importantly, the simple GP73 measurement proved promising for predicting a worse outcome of patients with both viral and non-viral chronic liver diseases.

OP0118 DECIPHERING THE ANTI-PROTEIN-ARGININE DEIMINASE (PAD) RESPONSE IDENTIFIES PAD1 AND PAD6 AS NOVEL AUTOANTIGENS IN RHEUMATOID ARTHRITIS

Background:Protein-arginine deiminase (PAD) 4 enzymes play a central role in the pathogenesis of rheumatoid arthritis (RA) and represents an antigenic target. Among the five known family members (PAD1, PAD2, PAD3, PAD4 and PAD6), only PAD2, PAD3 and PAD4 have been described to have autoantigenic properties. Furtheremore, very little is known on the the isotype usage of these autoantibodies. Understanding the molecular basis of the anti-PAD antibody reponse has the potential to open novel approaches for precision medicine in RA.Objectives:The objectives of this study were to screen for the presence of antibodies to the five PAD family members and to evaluate the isotype usage of the anti-PAD4 response in RA.Methods:First, we developed a panel for the detection of anti-PAD IgG based on a particle-based multi-analyte technology (PMAT), that utilized paramagnetic particles coupled with the different human recombinant PAD proteins (PAD1, PAD2, PAD3, PAD4 and PAD6) and anti-human IgG conjugate. This panel was used to test sera from RA patients (n=33) and non-RA controls (n=36). The controls were comprised of apparently healthy individuals (n=10), and patients with infectious diseases (n=10), systemic lupus erythematosus (n=7), systemic sclerosis (n=9) and Sjogren’s syndrome (n=1). Next, the PAD4-coupled beads were tested with anti-human IgM, IgA and IgG conjugates on an extended cohort of RA patients (n=62) and the same non-RA controls.Results:All five anti-PAD IgG (Figure 1) demonstrated the ability to discriminate between RA patients and controls. At greater than 90% specificity, anti-PAD4 IgG, followed by anti-PAD3 IgG, showed the best diagnostic performance. Significantly higher levels of the five antibodies were observed in RAvs.controls (p-values of 0.0041, &lt;0.0001, 0.0014, 0.0039, and 0.0140 for anti-PAD1, 2, 3, 4 and 6, respectively). Significant correlation was observed between all the antibodies, with the highest between anti-PAD1 and anti-PAD4 (Spearman´srho=0.87,p&lt;0.0001) and the lowest between anti-PAD4 and anti-PAD2 (Spearman’srho=0.38,p=0.0015) and anti-PAD4 and anti-PAD6 (Spearman’srho=0.38,p=0.0011). While principal component analysis (PCA) (Figure 2) showed an association between all anti-PAD antibodies, there was further discrimination that displayed closer association between anti-PAD1, 3 and 4 on one hand, and between anti-PAD2 and 6. For the extended testing of anti-PAD4 with IgG, IgA and IgM, all three isotypes were identified in the sera of RA patients. Higher levels of the three isotypes were observed in RA patients with erosive disease when compared with the patients without erosion, but this association was only significant for anti-PAD4 IgA (p=0.0086).Figure 1.Receiver operating characteristics (ROC) analysis of the discrimination between rheumatoid arthritis (RA) and controls of IgG to protein-arginine deiminase (PAD) 1, PAD2, PAD3, PAD4 and PAD6. The area under the curve (AUC) values are shown in brackets for each biomarker.Abbreviations:TPF: true positive fraction; FPF: false positive fractionFigure 2.Two dimensional principal component analysis (PCA) plot of the anti-PAD levels in RA patients (n=33) and controls (n=36). Anti-PAD1, 3 and 4 have the main contribution to PC1, which explains 51.7% of the variance, and anti-PAD2 and 6 to PC2, that represents 20.8% of it.Abbreviations:PC: principal componentConclusion:Our study is the first to describe PAD1 and PAD6 as novel antigenic targets in RA and to demostrate that the anti-PAD4 B-cell immune response uses all three isotypes (IgG, IgA and IgM). The strong and significant association between anti-PAD4 IgA and joint erosion is of particular clinical relevance.Disclosure of Interests:Laura Martinez-Prat Employee of: I am an employee of Inova Diagnostics, an in vitro diagnostics company., Mary Ann Aure Employee of: I am an employee of Inova Diagnostics, an in vitro diagnostics company., Chelsea Bentow Employee of: I am an employee of Inova Diagnostics, an in vitro diagnostics company., David Lucia Employee of: I am an employee of Inova Diagnostics, an in vitro diagnostics company., Marcos Lopez-Hoyos Consultant of: Inova Diagnostics, an in vitro diagnostics company., Michael Mahler Employee of: I am an employee of Inova Diagnostics, an in vitro diagnostics company.

THU0112 DIAGNOSTIC PERFORMANCE OF ANTI-CYCLIC CITRULLINATED PEPTIDE (CCP) 2 AND CCP3.1 ASSAYS IN EARLY RHEUMATOID ARTHRITIS

Background:Anti-cyclic citrullinated peptide (CCP) antibodies are the most specific markers for rheumatoid arthritis (RA). Different generations of assays have been developed among which the anti-CCP2 and anti-CCP3 assays are most widely used.Objectives:Since some differences between these assays have been reported it was our aim to compare their diagnostic performance and evaluate their usefulness for diagnostics of early RA.Methods:The anti-CCP3.1 assay (Quanta Lite®CCP3.1 IgG/IgA, Inova Diagnostics) was compared to anti-CCP2 IgG and IgA assays (EliATMCCP, Thermo Fisher Scientific) employing sera of 184 early RA patients, 360 disease controls and 98 healthy subjects.Results:Anti-CCP2 IgG and IgA assays showed high specificity versus healthy subjects (98.9%; 98%) and disease controls (98.8%; 99.4%). Sensitivity was 52.2% for the IgG and 30.4% for the IgA assay, respectively, resulting in high positive likelihood ratios (LR+) of 47.5 (IgG) and 50.7 (IgA). However, IgA antibodies did not show an added diagnostic value since all positive patients were also IgG positive. The anti-CCP3.1 assay was slightly more sensitive than the anti-CCP2 IgG assay (55.4%) but specificity was markedly lower and amounted to 95.9% versus healthy subjects and 90.8% versus disease controls resulting in a LR+ of only 6.0. Out of 360 disease controls 33 (9.2%) were found to be positive for CCP3.1 but among these only four (1.1%) were positive for anti-CCP2 IgG (and 2 of these also for anti-CCP2 IgA). The most common diagnosis of CCP3.1 positive control patients was osteoarthritis (12 patients); six patients suffered from spondyloarthropathies, two patients had reactive arthritis, 10 patients were diagnosed with an autoimmune rheumatic disease (AI RMD) and two patients had osteoporosis. However, at a cut-off of 60 AU/ml only nine disease controls remained positive (3 OA, 1 SpA, 4 AI RMD, 1 ReA) and 3 of them were also positive in the anti-CCP2 assay (ReA, SpA, SLE). When applying 60 AU/ml (high positive) as cut-off value at the early RA cohort, sensitivity (52.7%) became comparable to the anti-CCP2 assay and both specificity (97.5%) and LR+ (21.08) increased substantially.Conclusion:When interpreting the results of anti-CCP assays disease specificity should be taken into account in order to reduce the risk of misclassification and a false positive diagnosis.Table 1.Specificity, sensitivity and positive likelihood ratio (LR+) of CCP2 (IgG, IgA) and CCP3.1 assays.CCP3.1CCP2 IgGCCP2 IgACut-off (U/ml)201010Patients positive (n)1029656Specificity % (healthy subjects)95.999.098.0Specificity % (disease controls)90.898.999.4Sensitivity %55.452.230.4LR+ (healthy)13.552.015.2LR+ (disease controls)6.047.550.7Disclosure of Interests:Daniela Sieghart Grant/research support from: Thermo Fisher Scientific, Speakers bureau: Thermo Fisher Scientific, Christian Konrad Employee of: Thermo Fisher Scientific, Sascha Swiniarski Employee of: Thermo Fisher Scientific, Helmuth Haslacher: None declared, Daniel Aletaha Grant/research support from: AbbVie, Novartis, Roche, Consultant of: AbbVie, Amgen, Celgene, Lilly, Medac, Merck, Novartis, Pfizer, Roche, Sandoz, Sanofi Genzyme, Speakers bureau: AbbVie, Celgene, Lilly, Merck, Novartis, Pfizer, Sanofi Genzyme, UCB, Günter Steiner Grant/research support from: Thermo Fisher Scientific, Speakers bureau: Thermo Fisher Scientific

P239 Third generation APCA improve prediction of clinical arthritis in at-risk individuals with positive second generation ACPA

Abstract Background Anti-citrullinated peptide antibodies (ACPA) are important biomarkers in rheumatoid arthritis (RA) and can predict arthritis development in at-risk individuals. ACPA are conventionally detected using the second-generation or third generation IgG anti-CCP antibody (Ab) assays. Although the value of anti-CCP2 Ab for predicting progression to RA in at-risk individuals is well understood, very little knowledge exists for anti-CCP3.The objectives of this study were: i) To evaluate the prevalence of serum anti-CCP3 Ab in serum anti-CCP2 Ab positive at-risk individuals (CCP2+ at-risk); ii)) To study the incremental value of anti-CCP3 Ab in CCP2+ at-risk subjects for predicting progression to clinical inflammatory arthritis (IA). Methods Anti-CCP3 Ab were tested on stored serum samples obtained from 347 CCP2 + (BioRad, USA) at-risk individuals from the Leeds CCP study. Anti-CCP2 and anti-CCP3 tests positivity threshold was &amp;gt;2.99 IU/ml and &amp;gt;20 units, respectively. Moreover, anti-CCP2 and anti-CCP3 titres were categorised according to manufacturer’s cut-off: low (LT) and high (HT) for anti-CCP2, negative/weak/moderate/strong for anti-CCP3. Progression to IA was defined as the development of clinical synovitis in at least one joint. Only subjects with at least one follow-up visit were included in the progression analysis (n = 317). Results Anti-CCP3 Ab were negative in 138/347 (39.7%) CCP2+ individuals, and weakly, moderately, and strongly positive in 15/347 (4.3%), 5/347 (1.4%) and 189/347 (54.4%) individuals, respectively. LT and HT anti-CCP2 Ab were found in 103/347 (29.7%) and in 244/347 (70.3%) individuals, respectively. Eighty-eight/317 subjects (28%) developed IA. The rate of progression of LT and HT anti-CCP2, when anti-CCP3 was negative, decreased from 6.5% to 2.7%, and from 36.6% to 9.4%, respectively. Progression in anti-CCP2 HT increased from 36.6% to 45.6% when anti-CCP3 was positive (Table 1). Conclusion Our results support an important role for anti-CCP3 Ab in improving prediction of IA in CCP2+ at-risk individuals. Disclosures A. Di Matteo None. K. Mankia None. L. Duquenne None. M. Mahler Other; Inova Diagnostic. D. Corscadden None. K. Mbara None. L. Garcia-Montoya None. J. Nam None. P. Emery Honoraria; AbbVie, BMS, Bristol-Myers Squibb, Gilead, Lilly, MSD, Novartis, Pfizer, Roche, Samsung, Samsung Bioepis Co., Ltd.

Optimization of serologic diagnosis of celiac disease in the pediatric setting.

The clinical presentation of celiac disease (CD) varies between children. The objective of this study was to document the pre-test probability for CD based on symptoms and routine laboratory test and to evaluate the performance of two IgA anti-tissue transglutaminase (tTG) assays. We critically reviewed the concept of using multiples of the manufacturer's upper limit of normal (ULN), as proposed in the ESPGHAN guidelines (if IgA tTG is >10 times ULN, no biopsy is needed). The retrospective study included 91 children with newly diagnosed CD and 605 controls (<16 years). All underwent upper endoscopy with small bowel biopsies. Four laboratory parameters and 16 symptoms were registered. All patients were tested for IgA anti-tTG antibodies with assays from Inova Diagnostics and Thermo Fisher Scientific. Some combinations of clinical symptoms and laboratory parameters had a high pre-test probability for CD, such as (combinations of) anorexia, failure to thrive, low ferritin level and elevated AST. The diagnostic performance of both IgA anti-tTG assays was excellent and comparable (no difference in ROC curve area under the curve). At a threshold that corresponds to a specificity of 100% (5 times ULN for Inova Diagnostics and 2 times ULN for Thermo Fisher), the sensitivity was 82% for both assays. At the 10 times ULN threshold, the sensitivity differed between the assays (77% vs. 57%), indicating that such threshold does not completely align interpretation across companies. Our study showed that some combinations of symptoms and aberrant laboratory parameters had a high pre-test probability. The use of the ESPGHAN non-biopsy approach could reduce small bowel biopsies, but thresholds for IgA-tTG levels are not aligned across assays and should be based on predefined likelihood ratios or specificity.

A161 MACROSCOPIC AND HISTOLOGY FINDINGS DURING UPPER DIGESTIVE ENDOSCOPY IN CHILDREN WITH SUSPICION OF CELIAC DISEASE AND HIGH LEVELS OF TRANSGLUTAMINASE IGA-ANTIBODY

Abstract Background The European Society of Pediatric Gastroenterology Hepatology and Nutrition suggests that the diagnosis of Celiac disease (CD) can be confirmed solely on the basis of clinical symptoms and bloodwork including a level of transglutaminase IgA-antibodies (TGA) ≥ 10 times the upper limit of normal (10XN). In Canada and the United States, this recommendation has not been endorsed. We recently demonstrated that TGA ≥ 10XN performed at our institution (INOVA Diagnostics’ Quanta Lite) was a reliable predictive test of villous atrophy in patients with suspicion of CD. Aims The aim of the present study was to investigate the rate of supplemental endoscopic or histological findings in a cohort of children with TGA ≥ 10XN and the association of these findings with clinical symptoms. Methods Consecutive children with suspected CD who had an endoscopy between 2011 and 2018 were included in this analysis. Data was extracted from our CD database. The macroscopic and histological findings were reported. We compared these diagnoses to the clinical symptoms. Results From 2011 to 2018, 405 new cases of CD were identified in our pediatric center. In total, 238 (58.7%) patients had baseline TGA levels ≥ 10XN (67.2% females, median (IQR) age 8.4 (4.8–12.2)). The median interval between the first visit to the gastroenterology unit and the endoscopy was 43.0 (21.0–78.0) days. In total, 58% of the endoscopies had macroscopic findings in the bulb (37.8 %) or the duodenum (41.5%) including a mosaic pattern, mucosal fissuring, or erythema. Seven cases (2.8%) of esophagitis were identified during endoscopy; histological analysis confirmed eosinophilic esophagitis in 3 cases (1.2%) and peptic esophagitis in 4 cases. Non-specific gastritis was present in 58 patients (24.4%) and 2 cases of Helicobacter pylori infection were identified. The biopsies showed subtotal/total villous atrophy of duodenum in 171 (71.8%) or partial villous atrophy in 51 patients (29.8 %). Ten patients (4,3%) had villous atrophy in the duodenal bulb alone, with normal biopsies of the second part of the duodenum. Abdominal pain did not correlate with gastritis or duodenitis. However, children with diarrhea had a greater prevalence of visible endoscopic inflammation in the duodenum than those without diarrhea: 53.5% vs 38.9% respectively; P= 0,037. Conclusions Apart from the classical features associated with CD, the supplementary diagnostic yield of endoscopy was low. There were only a few cases of additional diseases identified by the endoscopic procedure in a large cohort of children and adolescents with suspicion of CD. Therefore, these results support the no-biopsy approach in the settings of TGA ≥ 10XN using a reliable diagnostic kit. Funding Agencies None

A five-year retrospective audit of anti-myeloperoxidase antibody titres measured using a commercial chemiluminescent immunoassay

Background: In 2015, ACT Pathology transitioned to a commercial chemiluminescent immunoassay (QUANTA-Flash MPO, Inova Diagnostics) to measure anti-MPO IgG antibodies. Monitoring of internal performance check sera identified discordant results following a change in reagent lot. To investigate this further, we conducted a five-year retrospective audit of all anti-MPO titres measured using this assay. Methods: Samples were stratified according to titre (negative <6 IU/mL, low-positive 6–23 IU/mL and high-positive ≥24 IU/mL), clinical information provided on request forms, ANCA pattern as detected by indirect immunofluorescence (IIF), and reagent lot number. Results: A total of 2005 anti-MPO titres were measured between 15 May 2015 and 13 August 2019. The mean number of tests performed each month doubled between 2015–2016 (25 tests/month) to 2017–2019 (50 tests/month). This was associated with increased testing of patients with known AAV. Some variation in the percentage of low-positive (5.8–16.4%) and high-positive (7.7–21.4%) results was observed between the 12 reagent lots used, however this may have been confounded by duration of use (range 2–296 days). The predicted probability of p-ANCA detection was significantly higher in patients with higher anti-MPO IgG titres (OR=17.66, 95% CI 13.72–21.13, p<0.0001). Conclusion: Anti-MPO IgG testing at ACT Pathology has increased over the last five years. While some variation between reagent lots has been observed, this has not significantly affected overall assay performance.

Evaluation of a novel particle-based assay for detection of autoantibodies in idiopathic inflammatory myopathies

BackgroundMyositis specific antibodies (MSA) represent not only important diagnostic tools for idiopathic inflammatory myopathies (IIM), but also help to stratify patients into subsets with particular clinical features, treatment responses, and disease outcome. Consequently, standardization of MSA is of high importance. Although many laboratories rely on protein immunoprecipitation (IP) for the detection of MSA, IP standardization is challenging and therefore reliable alternatives are mandatory. Recently, we identified significant variation between IP and line immunoassay (LIA) for the detection of MSA and myositis associated antibodies. In this study we aimed to compare the results from our previous study to the results obtained with a novel fully automated particle-based technology for the detection of MSA and MAA. MethodsA total of 54 sera from patients with idiopathic inflammatory myopathy (IIM) were tested using three methods: IP, LIA (Euroimmun, Germany) and a novel particle-based multi-analyte technology (PMAT, Inova Diagnostics, US, research use only). The analysis focused on antibodies to EJ, SRP, Jo-1, NXP-2, MDA5, TIF1-γ, and Mi-2. ResultsSignificant variations were observed among all methods. Overall, the novel PMAT assays showed slightly better correlation with IP, but the kappa agreement was strongly dependent on the antibody tested. When the results obtained from IP were used as reference for receiver operating characteristic (ROC) curve analysis, good discrimination and a high area under the curve (AUC) value were found for PMAT (AUC = 0.83, 95% confidence interval, CI 0.70-0.95) which was significantly higher (p = .0332) than the LIA method (AUC = 0.70, 95% CI 0.56–0.84). ConclusionThe novel PMAT used to detect a spectrum of MSA in IIM represents a potential alternative to IP and other diagnostic assays. Additional studies based on larger cohorts are needed to fully assess the performance of the novel PMAT system for the detection of autoantibodies in myositis.

Two Novel Technologies for the Detection of Anti-cardiolipin and Anti β2–Glycoprotein Antibodies in the Real Life: Chemiluminescent in Comparison to the Addressable Laser Bead Immunoassays

ABSTRACTIn the present study, we evaluated two novel technologies, the chemiluminescent immunoassay (CIA) QUANTA Flash on BIO-FLASH (Inova Diagnostics, San Diego, CA, USA) and the addressable laser bead immunoassay (ALBIA) on BioPlex™ 2200 (Bio-Rad, Hercules, CA, USA) for the detection of anti-cardiolipin IgG/IgM (aCL) and anti-β2–glycoprotein IgG/IgM (aβ2GPI) antibodies. The study was performed on 134 samples from consecutive patients (59 males and 75 females, mean age 54 ± 10 years) who consulted a rheumatologist because thrombosis and/or pregnancy complications were present or another immunological disease (Sjogren’s syndrome, inflammatory arthritis). Fourteen patients of the total fulfilled 25the Sydney criteria for APS and for these patients previous results of aPLs were available. Sera were tested for aCL and aβ2GPI of IgG and IgM isotypes using CIA (BIO-FLASH) and ALBIA (BioPlex™ 2200). Overall agreement between CIA and ALBIA ranged from 88.1% (aCL IgG) to 97.8% (aβ2GPI IgG). Cohen’s kappa coefficient ranged from 0.53 to 0.91, implying moderate to almost perfect agreement. Almost perfect agreement was found between BioPlex™ 2200 and BIO-FLASH aβ2GPI IgG and aCL IgM with Cohen’s kappa of 0.91 and 0.88, respectively. On the other hand, moderate agreement was found between BioPlex™ 2200 and BIO-FLASH aCL IgG and β2GPI IgM assays with Cohen’s kappa of 0.57 and 0.53, respectively. The two novel technologies look promising and comparable but further studies with larger cohorts are needed to contribute to the better understanding of the new aPLs antibodies assays performance.

Only monospecific anti-DFS70 antibodies aid in the exclusion of antinuclear antibody associated rheumatic diseases: an Italian experience.

Background The dense fine speckled (DFS) is one of the most common patterns that can be observed as a result of the anti-nuclear antibodies (ANA) test on HEp-2 cells and is mostly caused by antibodies to DFS70 as the main antigenic target. As was recently demonstrated, isolated anti-DFS70 positivity can be used as an aid in the exclusion of ANA associated rheumatic diseases (AARD) due to the opportunity to better interpret unexplained positive IIF ANA results. Methods Our study included 333 subjects with AARD, 51 undifferentiated connective tissue disease (UCTD) patients, 235 disease controls and 149 healthy blood donors from an Italian cohort. All samples were tested for anti-DFS70 and anti-ENA antibodies using QUANTA Flash assays (Inova Diagnostics, San Diego, CA, USA). Results No differences in the prevalence of anti-DFS70 antibodies were seen among AARD, non-AARD and UCTD (2.1% [7/333] vs. 2.3% [9/384] vs. 5.9% [3/51], respectively; p-value = 0.188). AARD patients positive for anti-DFS70 antibodies showed in all cases an accompanying anti-ENA specificity. In contrast, monospecific anti-DFS70 antibodies showed a significantly different distribution with a clear trend across the main groups (AARD vs. non-AARD vs. UCTD: 0% [0/7] vs. 22% [2/9] vs. 100% [3/3], p = 0.007). Anti-DFS70 antibody levels among AARD, non-AARD and UCTD patients were not significantly different (p = 0.094). Within the anti-DFS70 antibody positive cases, AARD cohort showed a higher variability (median [min-max]: 3.2 [3.2-450.8] CU) compared to non-AARD (median [min-max]: 3.2 [3.2-75.7] CU) and UCTD patients (median [min-max]: 3.2 [3.2-59.0] CU). Conclusions Our preliminary data showed a similar frequency of anti-DFS70 antibodies in AARD, UCTD and non-AARD cohorts. Monospecificity of anti-DFS70 antibodies but not their mere presence is the key element in the diagnostic algorithm. Mono-specific anti-DFS70 antibodies might be a helpful biomarker to discriminate individuals with AARD from non-AARD presenting with a positive ANA.

Autoantibodies to Mi-2 alpha and Mi-2 beta in patients with idiopathic inflammatory myopathy.

The objective of this study was to compare the results obtained from different assays for the detection of anti-Mi-2 antibodies, which are important markers in the diagnosis of DM. The study included 82 patients (68 females/14 males), most of whom had DM (n = 57), followed by PM (n = 16) and juvenile DM (n = 9). All samples were tested using a novel particle-based multi-analyte technology (PMAT) (Inova Diagnostics, research use only) in parallel with a line immunoassay (LIA: Euroimmun). To assess clinical specificity for the PMAT assay, a total of 775 disease and healthy controls were tested. 29 samples were positive by at least one test for anti-Mi-2 antibodies. Of those, 24 were Mi-2β LIA+, five were Mi-2α LIA+ and 23 Mi-2 PMAT+. The comparison shows varying agreement between the different methods (kappa 0.27-0.77). When LIA results were used as reference for receiver operating characteristics analysis, high area under the curve values were found for both PMAT vs LIA Mi-2α and LIA Mi-2β. When analysing the results in the context of the myositis phenotype, PMAT associated closest with the DM phenotype. In the control group, 3/775 controls (all low levels) were anti-Mi-2+ resulting in a sensitivity and specificity of 28.1% and 99.6%, respectively. Overall, good agreement was found between LIA and PMAT for anti-Mi-2 antibodies, which is important for the standardization of autoantibodies. Anti-Mi-2β antibodies measured by PMAT tend be more highly associated with the clinical phenotype of DM.

Increased prevalence of anti-DFS70 antibodies in young females: experience from a large international multi-center study on blood donors.

Background Isolated antibodies to DFS70 have been described in healthy individuals and are rarely found in patients with antinuclear antibody-associated autoimmune rheumatic diseases (AARD). However, no data is available on geographic differences in the prevalence of anti-DFS70 antibodies. We aimed to study the prevalence of anti-DFS70 antibodies in blood donor samples from several countries representing various ethnical backgrounds and geographic regions in the world. Methods Sera from apparently healthy blood donors (n≥300 per site) were collected in seven countries (USA, Italy, Spain, Germany, UK, Belgium and Brazil). All samples (n=2628) were tested for anti-DFS70 antibodies by QUANTA Flash DFS70 (Inova Diagnostics, Inc., San Diego, CA, USA). Results The prevalence of anti-DFS70 antibodies varied from 4/321 (1.2%, Italy) to 42/497 (8.5%, USA). Consequently, the prevalence of the antibodies was significantly higher in USA compared to all other countries (p<0.05). In addition, the prevalence in the combined cohort (all sites) was higher in young blood donors (<35 years; 5.0% vs. 2.7%; p=0.0017) and among females (4.5% vs. 3.0%; p=0.0446). However, when cohorts from different countries were corrected for age and gender, no significant difference between the countries were found. Conclusions This is the first study to analyze the prevalence of anti-DFS70 antibodies in different geographic areas using a standardized assay. Our findings show that the antibodies are most prevalent in young females.

Harmonizing by reducing inter-run variability: performance evaluation of a quality assurance program for antinuclear antibody detection by indirect immunofluorescence.

Background The introduction of automated anti-nuclear antibody (ANA) indirect immunofluorescence (IIF) analysis may allow for more harmonized ANA IIF reporting, provided that a thorough quality assurance program controls this process. The aim of this study was to evaluate various quality indicators used for ANA IIF analysis with the final goal of optimizing the iQC program. Methods In an experimental setup, we introduced artificial errors, mimicking plausible problems during routine practice on a QUANTA-Lyser-NOVA View® system (Inova Diagnostics, San Diego, CA, USA). Predetermined quality indicators were evaluated against predefined acceptance criteria. In addition, we retrospectively investigated the applicability of the selected quality indicators in the daily routine practice during three pre-defined periods. Results Both the experimental as the retrospective study revealed that pre-analytical, analytical and post-analytical errors were not highlighted by company internal quality control (iQC) materials. The use of patient derived iQC samples, median fluorescence intensity results per run and the percentage of positive ANA IIF results as additional quality indicators ensured a more adequate ANA IIF quality assurance. Furthermore, negative and moderate positive sample iQC materials merit clinical validation, as titer changes of >1 correspond to clinically important shifts. Traditional Westgard rules, including a clinically defined stop limit, revealed to be useful in monitoring of the supplemental quality indicators. Conclusions A thorough ANA IIF quality assurance for daily routine practice necessitates the addition of supplemental quality indicators in combination with well-defined acceptance criteria.

Two-Parametric Immunological Score Development for Assessing Renal Involvement and Disease Activity in Systemic Lupus Erythematosus.

Objective Anti-double-stranded (ds) DNA and anti-C1q autoantibodies are useful tools in the assessment of disease activity and nephritis in systemic lupus erythematosus (SLE) patients. This study aimed to explore the utility of these antibodies along with anti-Ku antibodies in an oligoparametric model approach for the assessment of disease activity and lupus nephritis. Methods Samples from 261 well-characterized SLE patients were tested using chemiluminescent immunoassays (CIA) for anti-dsDNA and anti-Ku antibodies as well as by anti-C1q antibody ELISA (Inova Diagnostics, USA). Of these SLE patients, 26.4% had lupus nephritis (LN) at the time of blood draw or had a history of LN, and modified SLE disease activity index-2K (SLEDAI) scores were used to assess disease activity. Results All three antibodies demonstrated higher prevalence and higher antibody levels in active versus inactive SLE patients and in LN versus non-LN patients. When oligoparametric analysis was performed, the likelihood of LN and patients with active disease increased with dual and triple positivity. Conclusions Anti-dsDNA and anti-C1q antibodies are useful tools to identify disease activity and/or renal involvement in SLE patients. In addition, the combination of those antibodies in a two-parametric score might improve the clinical utility of those markers.

Comparison of second- and third-generation immunoassays for detection of anti-cyclic citrullinated peptide antibodies

Anti-cyclic citrullinated peptide antibodies (anti-CCPs) are important diagnostic markers for rheumatoid arthritis (RA). We evaluated the analytical and clinical performance of the QUANTA Flash CCP3 (INOVA Diagnostics, USA), a fully automated third-generation anti-CCP assay, in comparison with three second-generation anti-CCP (CCP2) assays. A total of 300 sera (67 from RA patients, 64 from other rheumatic diseases, 43 from osteoarthritis [OA], and 126 from other conditions) were tested with QUANTA Flash CCP3, Kallestad Anti-CCP II (Bio-Rad, USA), Elecsys Anti-CCP (Roche Diagnostics GmbH, Germany), and ARCHITECT Anti-CCP (Abbott Diagnostics, USA). Within-run and total imprecision (% coefficient of variation) of the QUANTA Flash CCP3 were <6%, and its linearity was acceptable over the claimed range (4.0–2,749.7 chemiluminescent units). The frequency of anti-CCP was similar between QUANTA Flash CCP3 and the other CCP2 assays in the RA (67.2% vs. 62.7–70.1%), other rheumatic diseases (7.8% vs. 6.3%), and OA (2.3% vs. 0–2.3%) groups. The concordance rate between QUANTA Flash CCP3 and the other assays ranged from 96.3% to 97.7% (kappa from 0.87 to 0.92). For the diagnosis of RA, the sensitivity/specificity was 67.2%/95.7%, 62.7%/98.3%, 70.2%/96.6%, and 67.2%/97.9%, and the areas under the receiver operating characteristic curves were 0.851, 0.791, 0.853, and 0.867 for QUANTA Flash CCP3, Kallestad, Elecsys, and ARCHITECT assays, respectively. The performance of the QUANTA Flash CCP3 was satisfactory and comparable to that of the three CCP2 assays. This fully automated assay would be a practical and reasonable option in clinical laboratories.

A better definition of the anti-DFS70 antibody screening by IIF methods

BackgroundAnti-DFS70 antibodies have been recently included in a new testing algorithm for patients with suspicion of connective tissue diseases (CTDs). This algorithm enables to assess the probability of having a CTD in patients with a positive antinuclear antibodies (ANA) result. The aim of the study was to analyze the the inter-method agreement between three different HEp-2 cell substrates for anti-DFS70 detection, focusing on two novel IIF methods that assess the presence of monospecific anti-DFS70 antibodies. MethodsImmunological and clinical records of 29 patients who were double positive for anti-DFS70 autoantibodies using chemiluminescence assay (CIA) and Immunoblot (IB) were studied. The IIF on HEp-2 cells were determined using slides from Inova Diagnostics, Euroimmun and Immco. The capability to detect isolated anti-DFS70 antibodies was compared using immunoadsorption on NOVA Lite HEp-2 Select (Inova Diagnostics) and the HEp-2 ELITE/DFS70 knockout test (Immco). ResultsThe three substrates had very good sensitivity for detecting patients with anti-DFS staining pattern (93.1%, 79.3% and 72.4% for Euroimmun, Immco and Inova respectively). Most of the patients had full inhibition of DFS pattern (65.5%) by immunoabsorption test. Also, the 55.2% of the subjects were positive for monospecific DFS pattern using HEp-2 ELITE/DFS70 knockout test. However, the correlation between the full inhibition by immunoadsorption and the monospecific DFS pattern in knockout cells was very low (kappa: 0.22). ConclusionThe evaluation of monospecific anti-DFS70 antibodies is clinically fundamental and challenging using traditional HEp-2 IIF. Results obtained in this study support the hypothesis that the lack of standardization across IIF kits along with the subjectivity of user interpretation among other factors contribute to the overall reduction in the agreement.

The association of solid-phase assays to immunofluorescence increases the diagnostic accuracy for ANA screening in patients with autoimmune rheumatic diseases

Abstract Aim This study aimed to investigate whether it is useful both for diagnostic purposes and for cost savings to associate a solid-phase monotest called CTD screen to the immunofluorescence (IIF) test, to detect anti-nuclear and anti-cytoplasmic antibodies (ANA). Methods Fifteen Italian laboratories participated in the study enrolling at least 250-each consecutive unselected samples from patients routinely referred for ANA testing. They all used the conventional IIF method on HEp-2 cells associated to a solid phase CTD screen method. Seven centers used the EliA FEIA CTD screen method on the Phadia 250 instrument (ThermoFisher), five centers used the QUANTAFlash CTD Screen method (Inova Diagnostics) on the BioFlash CLIA instrument, while three centers used both methods, albeit in two different series of patients. Results A total of 5043 samples were tested. We focused attention to the 1674 discrepant results: 106 (2%) were ANA-IIF negative/CTD screen positive and 1568 (31%) were ANA-IIF positive/CTD screen negative. Specific antibodies were detected in 87/106 (82%) of the ANA-IIF negative/CTD screen positive samples, mainly Ro52, Ro60, dsDNA, PM/Scl and Jo1. Thirty four of these patients were diagnosed with an ANA-associated autoimmune rheumatic disease (AARD) (seven SLE, 15 Sjӧgren's syndrome, nine autoimmune inflammatory myositis, three systemic sclerosis). Among 1568 ANA-IIF positive/CTD screen negative discrepant patients, a specific antibody was found in 94 (6%) samples (28 patients with AARD, 13 with undifferentiated connective tissue disease, two with undifferentiated arthritis, and 51 without a rheumatic disease). Conclusions This study is the first that compares the IIF method vs. solid-phase assays in the detection of ANA, on a very large sample size from the routine work-up (real-life approach). Results show that the association of solid-phase CTD screen tests to the ANA-IIF test increases the sensitivity (from 89.2% to 97.4%) and the specificity (from 64.6% to 98.4%) of serological tests for ANA screening. Analysis of costs demonstrated that combination of the two tests is also cost-effective, reducing global costs for the immunoserological diagnosis of AARD by 22%.

Analytical variability in the determination of anti-double-stranded DNA antibodies: the strong need of a better definition of the old and new tests.

Anti-dsDNA antibodies are a heterogeneous group of antibodies, quite specific for SLE. Their variability is related to the assay used, the immunoglobulin class secondary antibody, and the dsDNA source. The standardization of measuring anti-dsDNA antibodies is still poor and different methods yield different results. Several novel technologies were developed during the last decades that represent viable alternatives to the traditional methods such as the chemiluminescent immunoassay (CIA) and multiplex flow immunoassay (MFI). Additionally, positive results for anti-dsDNA antibodies can be detected in patients with inflammatory arthritis (IA) treated with different biologics reducing its clinical specificity for SLE. Anti-dsDNA antibody levels were evaluated in 246 patient samples: 70 SLE and 176 disease control (including 96 IA during treatment with different biologics), using three enzyme immunoassays (indirect enzyme immunoassay, Bio-Rad Laboratories; chemiluminescent immunoassay, Inova Diagnostics; multiplex flow immunoassay, Bio-Rad Laboratories) and three Crithidia luciliae immunofluorescence tests (CLIFT) (Euroimmun AG, Bio-Rad Laboratories, INOVA Diagnostics). Diagnostic performances were assessed both including and excluding the IA patients. Agreements, measured by the Cohen's Kappa between all methods, ranged from moderate to substantial (0.47-0.68). The clinical sensitivities for the anti-dsDNA antibody tests varied from 5.7% by CLIFT A up to 33.3% provided by EIA while the clinical specificities varied from 89.8% by MFI to 98.9% provided by CLIFT B and C. Newer technologies, such as MFI and CIA, showed great potential as a diagnostic application. Significant variations among anti-dsDNA antibody assays were observed confirming the lack of standardization.

Evaluation of classical and novel autoantibodies for the diagnosis of Primary Biliary Cholangitis-Autoimmune Hepatitis Overlap Syndrome (PBC-AIH OS).

Background and aimsUp to 20% of Primary Biliary Cholangitis (PBC) patients are estimated to have features that overlap with Autoimmune Hepatitis (AIH). Patients with PBC-AIH overlap syndrome (PBC-AIH OS) have been reported to exhibit suboptimal responses to ursodeoxycholic acid therapy, and are more likely to progress to cirrhosis. Anti-double stranded DNA (anti-dsDNA) and anti-p53 have been previously suggested to be potential autoantibodies for identifying patients with PBC-AIH OS. In our well defined PBC patient cohorts, a comprehensive assessment of various classical and novel autoantibodies was evaluated for their utility in identifying PBC-AIH OS patients.MethodsPBC-AIH OS was classified according to the Paris criteria and PBC as per the European Association for the Study of the Liver guidelines. Biobanked serum samples from 197 patients at the University of Calgary Liver Unit and the University of Alberta were analyzed for classical and novel autoantibodies. Anti-dsDNA was measured by the Crithidia luciliae immunofluorescence (CLIFT) assay (1:20 dilution) and chemiluminescence (CIA: QUANTA Flash®, Inova Diagnostics, San Diego). Anti-p53, anti-Ro52/TRIM21, anti-YB 1, anti-GW182, anti-Ge-1, and anti-Ago 2 were measured by either an addressable laser bead immunoassay (ALBIA) or line immunoassay (LIA). Autoantibodies against MIT3, gp210, sp100, LKM1, SLA, and the novel autoantibodies Hexokinase-1 (HK-1), and Kelch like protein 12 (KLHL-12) were measured using QUANTA Lite® ELISA assays. We applied non-parametric methods to compare the biomarkers frequencies between study groups. We used multivariate adjusted models and AUROC to compare the diagnostic accuracy of the different autoantibodies alone or in combination with serum biochemistry.Results16 out of 197 PBC patients (8.1%) were classified as PBC-AIH OS. Compared to PBC patients, PBC-AIH OS patients were similar in age (median: 59 vs. 63, P = 0.21) and female predominance (94% vs. 89%, P = 1.00). Anti-dsDNA-by CLIFT (37.5% in PBC-AIH OS vs 9.9% in PBC alone, P <0.01) was the only autoantibody associated with PBC-AIH OS; a finding consistent with previous reports. Significant elevation in serum ALT (62 IU/L in PBC-AIH OS vs 37 IU/L in PBC alone, P < 0.01), and serum IgG (17.6 g/L in OS vs 12.1 g/L in PBC alone, P <0.01) were observed in patients with PBC-AIH OS receiving medical/immunosuppressive therapy. In a multivariate model, positive anti-dsDNA by CLIFT, ALT and IgG were significant predictors of PBC-AIH OS with an area under the receiver operator curve (AUROC) value of 0.84.ConclusionsConsistent with previous findings, the presence of anti-dsDNA by CLIFT is associated with PBC-AIH OS. Contrary to previous reports, anti-p53 was not associated with PBC-AIH OS. Our comprehensive evaluation of various classical and novel autoantibody biomarkers including Ro52/TRIM21, anti-p53, anti-KLHL-12 and anti-HK-1 were not significantly associated with PBC-AIH OS. Our findings highlight the ongoing need for the research and development of new autoantibody biomarkers to aid in the diagnosis of PBC-AIH OS.