The Role of Indirect Immunofluorescence (IIF) and Line Immunoassay (LIA) in the Diagnosis of Autoimmune Diseases and Their Clinical Correlation: An Observational Study From a Tertiary Care Center in Bihar

Background and aim The presence of distinct sets of autoantigens and autoantibodies bestow these autoimmune diseases (ADs) with specific immune profiles or fingerprints, which has cleared the diagnostic dilemma associated with these ADs. This study was planned to collate and compare the reporting of indirect immunofluorescence (IIF) with line immunoassay (LIA) and their clinical correlations. This study was conducted to investigate the association between the reporting of anti-nuclear antibody (ANA) screening by IIF and ANA profile reporting by LIA. Additionally, it aimed to explore the association of ANA pattern detection by IIF with the detection of autoantibodies against nuclear antigens by LIA and the association of autoantibody detection by LIA with clinical diagnosis. Methodology A total of 98 samples from patients suspected of having ADs were subjected to both IIF and LIA, and results were correlated with clinical diagnosis. Results In the homogenous pattern noted by IIF, the clustered antigens identified by LIA included dsDNA, Nucleosome, Histone, and Mi-2. In the speckled pattern, the identified antigens were SS-A/Ro52, P0, SS-A/Ro60, SS-B/La, and U1-snRNP. On the other hand, the nucleolar pattern revealed antigens AMA M2, PCNA, and CENP-B. The centromere pattern was mostly associated with CENP-B. The speckled pattern was found to be most commonly associated with systemic lupus erythematosus (SLE). The most common autoantibody found in total ANA profile-positive samples was anti-U1-snRNP followed by anti-SS-A/Ro60 and anti-SS-B/La, and all three were found to be associated with SLE. Conclusions SLE was the most common AD identified in our study samples, with the speckled pattern being the most common pattern on IIF and anti-U1-snRNP being the most common ANA identified by LIA. The fluorescence pattern of IIF predicts the presence of specific antibodies. LIA should be reserved for IIF-positive but dubious cases and whose signs and symptoms are nebulous and do not match the disease dictated by IIF.

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.

Performance of myositis-specific antibodies detected on myositis line immunoassay to diagnose and sub-classify patients with suspected idiopathic inflammatory myopathy, a retrospective records-based review

AIM

To evaluate myositis line immunoassay (LIA) for diagnosis and sub-classification of suspected idiopathic inflammatory myopathy (IIM). To investigate if test performance is improved by increasing signal strength cut-off for myositis-specific antibody (MSA) or combining MSA with indirect immunofluorescence (IIF).

METHODS

A retrospective, consecutive case series of patients investigated for MSAs from June 2013 to June 2020 for suspected IIM. Specificity, sensitivity, positive predictive value, and negative predictive value were calculated with 95% confidence intervals for diagnosis of IIM. Association of IIM diagnosis with increased signal strength and presence of an expected IIF pattern on Hep-2 cells was assessed by Fisher's exact test in MSA-positive patients.

RESULTS

A total of 195 patients were evaluated. IIM was diagnosed in 32/195 (16.4%) patients. MSAs were detected in 41/195 (21%) patients, 18/41 (43.9%) patients with an MSA had a diagnosis of IIM. The probability of an IIM diagnosis was increased in MSA-positive patients with high compared with low signal strength (83.3% vs 43.5%; P = 0.01) and an expected compared with unexpected IIF pattern (61.5% vs 23.8%; P = 0.04). Specificity for IIM was not significantly improved by increasing signal strength cut-off (85.9% vs 93.8%). Positive predictive value of myositis LIA was only modest and not significantly improved by either increasing signal strength cut-off or requiring an expected IIF pattern for determination of MSA positivity (43.9% vs 60% vs 61.5%). Sub-classification of IIM correlated closely for respective MSAs (88.9%).

CONCLUSION

Increased MSA signal strength on myositis LIA and the presence of an expected IIF pattern were associated with IIM diagnosis. Test performance was non-significantly improved by these methods. Prevalence of IIM in this patient cohort was low; it is not excluded that LIA performance could be improved by these methods in a higher prevalence cohort.

Comparison of antinuclear antibody profiles obtained using line immunoassay and fluorescence enzyme immunoassay

Objective

LIA-ANA-Profile-17S is a multiplex line immunoassay that simultaneously detects 17 antinuclear antibodies (ANAs) against extractable nuclear antigens (ENAs). We evaluated the utility of LIA-ANA-Profile-17S as a supplement to ANA indirect immunofluorescence (IIF) and EliA ENA (a fluorescence enzyme immunoassay) for diagnosis of ANA-associated rheumatic diseases.

Methods

Sera were collected from 245 patients referred for an ANA IIF test. LIA-ANA-Profile-17S results were compared with those of EliA ENA. The kappa coefficients, agreement rates, and diagnostic performance of these tests were assessed for systemic lupus erythematosus (SLE) and Sjögren’s syndrome (SjS).

Results

We observed almost perfect interassay agreement for antibodies against Ro52/Ro60, CENP-B, and Scl-70 (kappa = 0.91, 0.97, and 1.00, respectively); strong agreement for anti-SS-B/La antibody (kappa = 0.81); and relatively low agreement for other antibodies, including those against dsDNA, Sm, RNP, and Jo-1. For SLE diagnosis, LIA-ANA-Profile-17S showed lower sensitivity and similar specificity compared with EliA ENA. The sensitivity and specificity of these two assays were similar for SjS diagnosis.

Conclusions

The specificity of LIA-ANA-Profile-17S was enhanced when combined with ANA IIF and was comparable with that of EliA ENA. LIA-ANA-Profile-17S showed relatively good agreement with EliA ENA. In combination with ANA IIF, these assays showed enhanced diagnostic performance.

Lack of standardisation in interpretation and reporting of autoantibody assays: a survey analysis of Australasian laboratories with focus on line immunoassays

Autoantibody assays are reported in a variety of formats. Results only slightly above established cut-offs provide lower likelihood ratios; therefore, their clinical significance may be more uncertain, which is not readily communicated with dichotomous qualitative reporting. Line immunoassays (LIA) are a common method for detecting antibodies to extractable nuclear antigens (ENA) and myositis-associated antibodies. However, recommended positive cut-offs are contentious. We distributed a survey via e-mail to participants in the Royal College of Pathologists of Australasia Quality Assurance Program (RCPAQAP) Immunology modules and to a dedicated immunology mailing list in Australasia. Questions explored general viewpoints surrounding autoantibody reporting, as well as current laboratory practices, with particular focus on interpretation and reporting of the most commonly used ENA LIA manufactured by Euroimmun. There were 31 responders, representative of at least 17 unique laboratories across Australia (8 public, 5 private) and New Zealand (4 laboratories). Responses suggest that autoantibody reporting is not standardised; there was variation in general viewpoints and reporting practices, particularly regarding the interpretation of and positive cut-offs used for the Euroimmun ENA LIA, which were contrary to the manufacturer's guidelines in a majority of the responses. Interpretative qualitative reporting based on results from other investigations and the clinical history was a common theme. There is large variation in the reporting of autoantibody assays within Australasia, especially by LIA. A majority of respondents report the most commonly used ENA LIA contrary to manufacturer's guidelines; alternative positive cut-offs are commonly utilised. LIA reports should indicate the level of positivity to enhance their relevance in the clinical decision-making process.

Current Promising Biomarkers and Methods in the Diagnostics of Antiphospholipid Syndrome: A Review

Antiphospholipid syndrome (APS) is a hypercoagulation condition associated with the incidence of heterogenic antiphospholipid antibodies (aPLs), which non-specifically affect hemostasis processes. APS is clinically manifested by recurrent arterial and venous thromboses and reproduction losses. The aPL antibodies, which may induce clinical manifestations of APS, include criteria antibodies anti-cardiolipin, anti-β2-glycoprotein-I, and lupus anticoagulant, but also non-criteria antibodies, for example anti-β2-glycoprotein-I domain I, anti-phosphatidylserine/prothrombin, anti-annexin V, and many others. APS occurs mostly in patients of younger and middle age, most frequently in females. Laboratory diagnostics of APS are quite difficult, as they include a wide spectrum of examining methods, which are based on various principles of detection and are performed using various laboratory techniques. The objective of the review is to describe the current state of potentially examined biomarkers and methods in APS diagnostics. The aforementioned biomarkers are lupus anticoagulant, anti-β2-glycoprotein-I, anti-cardiolipin, anti-β2-glycoprotein-I domain I, anti-phosphatidylserine/prothrombin, anti-β2-glycoprotein-I IgA, anti-cardiolipin IgA, anti-annexin V and II, anti-prothrombin, anti-cardiolipin/vimentin, anti-protein S/protein C, and antibodies against phospholipid antigens for whose diagnostics we may use some of the methods established for a long time and some of the modern methods—the coagulation method for the determination of lupus anticoagulant (LA), enzyme-linked imunosorbent assay (ELISA), chemiluminescence analysis (CLIA), multiplex fluorescence flow immunoassay (MFFIA), fluorescence enzyme immunoassay (EliA), line immunoassay (LIA), multiline dot assay (MLDA), and thin-layer chromatography (TLC). Conclusion: Antibodies against phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, cardiolipin/vimentin complex, and annexin V are currently the most studied new markers. However, these assays have not been standardized until now, both from the laboratory and clinical point of view. In this review we summarize the evidence of the most studied aPL markers and their potential clinical significance in seronegative APS (SN-APS).

A Strategy for Screening and Confirmation of HTLV-1/2 Infections in Low-Endemic Areas

Serological tests have been widely used for detecting human T-cell lymphotropic virus type 1/2 (HTLV-1/2) antibodies in the endemic areas, but their performance in low-risk populations is rarely reported. The aim of this study was to evaluate the performance of four HTLV-1/2 screening assays and to discuss a strategy for diagnosis of HTLV-1/2 infection in a non-endemic area. At the present study, 1546 specimens repeatedly reactive (RR) by one screening ELISA were collected from blood centers/banks from January 2016 to April 2019. Avioq-ELISA, Murex-ELISA, Roche-ECLIA and Fujirebio-CLIA were independently performed on each plasma sample and compared to WB and LIA confirmatory tests. Positive or indeterminate specimens with blood available were quantified by qPCR. The results showed that 48 samples were finally confirmed as HTLV-1 positive, 13 were HTLV positive, 151 were indeterminate, and 387 were negative. All the WB-positive samples were also LIA-positive. Roche-ECLIA showed the highest sensitivity that was able to detect 91.8% positives and combined with the Murex-ELISA would significantly increase the positive detection rate (98.4%). In addition, LIA yield more indeterminate and HTLV-untyped results than WB (152 vs. 27), but was able to resolve infection status of some individuals with an indeterminate WB. Besides, 3 WB indeterminate and 1 LIA-untyped samples were confirmed as HTLV-1 positive by qPCR. Based on these findings, we put forward a proper test strategy for HTLV-1/2 diagnosis in low-prevalence areas. If possible, the Roche-ECLIA with the highest sensitivity is suggested as a second screening assay in primary labs. If not, all RR specimens are recommended to be firstly retested by Roche-ECLIA and Murex-ELISA in the reference lab. Secondly, samples reactive to any one of the two tests were quantified by qPCR, and then the NAT-negatives were furtherly submitted to LIA for confirmation. Thereby, the cost can be reduced and the diagnostic accuracy would be improved.

Comparison of two extractable nuclear antigen testing algorithms: ALBIA versus ELISA/line immunoassay

Extractable nuclear antigen (ENA) antibody testing is often requested in patients with suspected connective tissue diseases. Most laboratories in Australia use a two step process involving a high sensitivity screening assay followed by a high specificity confirmation test. Multiplexing technology with Addressable Laser Bead Immunoassay (e.g., FIDIS) offers simultaneous detection of multiple antibody specificities, allowing a single step screening and confirmation. We compared our current diagnostic laboratory testing algorithm [Organtec ELISA screen / Euroimmun line immunoassay (LIA) confirmation] and the FIDIS Connective Profile. A total of 529 samples (443 consecutive+86 known autoantibody positivity) were run through both algorithms, and 479 samples (90.5%) were concordant. The same autoantibody profile was detected in 100 samples (18.9%) and 379 were concordant negative samples (71.6%). The 50 discordant samples (9.5%) were subdivided into 'likely FIDIS or current method correct' or 'unresolved' based on ancillary data. 'Unresolved' samples (n = 25) were subclassified into 'potentially' versus 'potentially not' clinically significant based on the change to clinical interpretation. Only nine samples (1.7%) were deemed to be 'potentially clinically significant'. Overall, we found that the FIDIS Connective Profile ENA kit is non-inferior to the current ELISA screen/LIA characterisation. Reagent and capital costs may be limiting factors in using the FIDIS, but potential benefits include a single step analysis and simultaneous detection of dsDNA antibodies.

Confirmation of anti-DFS70 antibodies is needed in routine clinical samples with DFS staining pattern

Background

Recognition of nuclear dense fine speckled (DFS) pattern by indirect immunofluorescence (IIF) is not easy. Thus, confirming the presence of these antibodies might be needed. In this study, we aimed to determine the frequency of DFS pattern in our diagnostic laboratory and to investigate the presence of anti-DFS70 antibodies in samples showing DFS pattern by two commercially available research kits retrospectively.

Material and methods

Seventy-four sequential serum samples with DFS pattern on HEp2010 cell substrates by IIF were included in this study. The semiquantitative DFS70 ELISA Kit (MBL International Corporation, Woburn, UK) was used for detection of anti-DFS70 antibodies in these samples. Twenty selected samples were tested for the presence of anti-DFS70 antibodies using ANA Line Immunoassay (LIA) (Immco Diagnostics, New York, USA).

Results

Sixty-two (83.8%) of 74 serum samples were found positive with ELISA, when 15 U/ml was taken as a reference value. Among 18 samples that were found positive by ELISA, five were negative for anti-DFS70 antibodies by LIA, while 13 were found positive. The lowest ELISA result of the sample that was positive by LIA was found to be 45.3 U/ml. When 45.3 U/ml was considered as a reference value, 45 (60.8%) of 74 serum samples were positive by ELISA. Nineteen of 20 patients had no SARD, while one had systemic lupus erythematosus (SLE).

Conclusions

DFS pattern should be confirmed with an objective method such as ELISA, LIA, or IB. We think that confirmation tests for detection of anti-DFS70 antibodies should be included in diagnostic algorithms.

Autoantibody profiling in APS

The international consensus for the classification of antiphospholipid syndrome (APS) requires clinical and laboratory criteria to be considered at an equal level for diagnosing APS. Thus, detection of antiphospholipid antibodies (aPL) being a hallmark of APS has been the object of intensive investigation over the past 40 years. However, appropriate detection of aPL still remains a laboratory challenge due to their heterogeneity comprising autoantibodies reactive to different phospholipid-binding plasma proteins, such as beta-2 glycoprotein I (β2GPI) and prothrombin. The relevance of aPL interacting with phospholipids other than cardiolipin (CL, diphosphatidylglycerol), such as phosphatidylserine (PS), remains elusive with regard to the diagnosis of APS. Recently, the concept of aPL profiling has been introduced to assess the risk of thrombotic complications in patients with APS. New assay techniques, apart from enzyme-linked immunosorbent assays (ELISAs) recommended by the international consensus for the classification of APS, have been proposed for multiplexing of aPL testing. Line immunoassays (LIAs) employing a novel hydrophobic solid phase for the simultaneous detection of different aPL seem to be an intriguing alternative. We evaluated a novel multiplex LIA employing a hydrophobic membrane coated with different phospholipid (PL)-binding proteins or PLs. The performance characteristics of this new multiplexing assay technique demonstrated its usefulness for aPL profiling.

PR3-ANCA: a promising biomarker for ulcerative colitis with extensive disease

BACKGROUND

We determined if PR3-ANCA is a biomarker that differentiates ulcerative colitis (UC) from Crohn's disease (CrD).

METHODS

A total of 946 sera were tested, including 86 granulomatosis with polyangiitis (GPA) and 491 inflammatory bowel disease (IBD) patients (283 UC and 208 CrD), 264 pathological controls (various diseases) and 105 healthy individuals. All samples were tested for PR3-ANCA by ELISA (QUANTA Flash Lite®, INOVA Diagnostics) and chemiluminescent immunoassays (CIA QUANTA Flash PR3). Conventional anti-neutrophil cytoplasmic antibody (ANCA) indirect immunofluorescence assays (IIF) was performed with NOVA Lite™ (INOVA Diagnostics).

RESULTS

PR3-ANCA by CIA were detected in 31.1% UC vs. 1.9% CrD sera (p=2.2E-16), and by ELISA in 6% UC and 0% CrD (p=0.0003). In GPA patients, PR3-ANCA were detected in 75.6% by CIA and 61.6% by ELISA (p<0.05). PR3-ANCA by CIA were more prevalent in E3-UC compared to E1/2-UC (p<0.05), and in patients with shorter disease duration (p<0.0001). PR3-ANCA showed similar sensitivity, but significantly higher specificity (p<0.05), compared to atypical pANCA by IIF.

CONCLUSION

The novel PR3 CIA may prove helpful in the differentiation of CrD from UC, as well as in the identification of UC patients with more extensive disease.