Diagnostic accuracy of commercially available serological tests for the detection of measles and rubella viruses: a systematic review and meta-analysis.

Measles and rubella serological diagnoses are done by IgM detection. The World Health Organization Global Measles and Rubella Laboratory Network previously endorsed Siemens Enzygnost enzyme-linked immunosorbant assay kits, which have been discontinued. A recommended replacement has not been determined. We aimed to search for suitable replacements by conducting a systematic review and meta-analysis of IgM detection methods that are currently available for measles and rubella. A systematic literature search was performed in Medline, Embase, Global Health, Cochrane Central, and Scopus on March 22 and on 27 September 2023. Studies reporting measles and/or rubella IgM detection with terms around diagnostic accuracy were included. Risk of bias was assessed using QUADAS tools. Meta-DiSc and R were used for statistical analysis. Clinical samples totalling 5,579 from 28 index tests were included in the measles meta-analysis. Sensitivity and specificity of the individual measles studies ranged from 0.50 to 1.00 and 0.53 to 1.00, respectively. Pooled sensitivity and specificity of all measles IgM detection methods were 0.94 (CI: 0.90-0.97) and 0.94 (CI: 0.91-0.97), respectively. Clinical samples totalling 4,983 from 15 index tests were included in the rubella meta-analysis. Sensitivity and specificity of the individual rubella studies ranged from 0.78 to 1.00 and 0.52 to 1.00, respectively. Pooled sensitivity and specificity of all rubella IgM detection methods were 0.97 (CI: 0.93-0.98) and 0.96 (CI: 0.93-0.98), respectively. Although more studies would be ideal, our results may provide valuable information when selecting IgM detection methods for measles and/or rubella.

Performance of two modified two-tier algorithms for the serologic diagnosis of Lyme disease.

We compared the performance of a new modified two-tier testing (MTTT) platform, the Diasorin Liaison chemiluminescent immunoassay (CLIA), to the Zeus enzyme-linked immunoassay (ELISA) MTTT and to Zeus ELISA/Viramed immunoblot standard two-tier testing (STTT) algorithm. Of 537 samples included in this study, 91 (16.9%) were positive or equivocal by one or more screening tests. Among these 91 samples, only 57 samples were concordant positive by first-tier screening tests, and only 19 of 57 were concordant by the three second-tier methods. For IgM results, positive percent agreement (PPA) was 68.1% for Diasorin versus 89.4% for Zeus compared to immunoblot. By contrast, the PPA for IgG for both Diasorin and Zeus was 100%. Using a 2-out-of-3 consensus reference standard, the PPAs for IgM were 75.6%, 97.8%, and 95.6% for Diasorin, Zeus, and immunoblot, respectively. The difference between Zeus MTTT and Diasorin MTTT for IgM detection was significant (P = 0.0094). PPA for both Diasorin and Zeus MTTT IgG assays was 100% but only 65.9% for immunoblot STTT (P = 0.0005). In total, second-tier positive IgM and/or IgG results were reported for 57 samples by Diasorin MTTT, 63 by Zeus MTTT, and 54 by Viramed STTT. While Diasorin CLIA MTTT had a much more rapid, automated, and efficient workflow, Diasorin MTTT was less sensitive for the detection of IgM than Zeus MTTT and STTT including in 5 early Lyme cases that were IgM negative but IgG positive. IMPORTANCE: The laboratory diagnosis of Lyme disease relies upon the detection of antibodies to Borrelia species. Standard two tier testing (STTT) methods rely upon immunoblots which have clinical and technical limitations. Modified two-tier testing (MTTT) methods have recently become available and are being widely adopted. There are limited independent data available assessing the performance of MTTT and STTT methods.

Refining Timely Diagnosis of Early Syphilis by Using Treponema pallidum PCR or IgM Immunoblotting Next to Conventional Serology for Syphilis.

Treponema pallidum subsp. pallidum is a fastidious spirochete and the etiologic agent of syphilis, a sexually transmitted infection (STI). Syphilis diagnoses and disease staging are based on clinical findings and serologic testing. Moreover, according to most international guidelines, PCR analysis of swab samples from genital ulcers is included in the screening algorithm where possible. It has been suggested that PCR might be omitted from the screening algorithm due to low added value. As an alternative to PCR, IgM serology might be used. In this study, we wanted to establish the added value of PCR and IgM serology for diagnosing primary syphilis. Added value was defined as finding more cases of syphilis, preventing overtreatment, or limiting the extent of partner notification to more recent partners. We found that both PCR and IgM immunoblotting could aid the timely diagnosis of early syphilis in ~24% to 27% of patients. PCR has the greatest sensitivity and can be applied to cases with an ulcer with suspected reinfection or primary infection. In the absence of lesions, the IgM immunoblot could be used. However, the IgM immunoblot has better performance in cases with suspected primary infection than in reinfections. The target population, testing algorithm, time pressures, and costs should determine whether either test provides sufficient value to be implemented in clinical practice.

Temporal virus serological profiling of kidney graft recipients using VirScan.

At this time, pretransplant viral screening of donors and recipients is based on serological status and limited to certain viruses. After transplantation, patient follow-up is based on a monitoring strategy using ELISA or PCR. Such approaches exclude other emerging viruses that can affect the transplant outcome. Recently, a multiplex unbiased array, VirScan, was developed. This tool allows the detection of antibodies against viruses, using a synthetic human virome, with minimal serum and cost. We decided to test the value of VirScan in the follow-up of a cohort of transplant recipients. We enrolled 45 kidney transplant recipients and performed virus serological profiling at day 0 and day +365, using VirScan. We compared the results obtained with ELISA/PCR assays. We detected antibody responses to 39 of the 206 species of virus present in the VirScan library, with an average of 12 species of virus per sample. VirScan gave similar results to PCR/ELISA screening tests. Using VirScan, we found that anti-viral antibody responses were largely conserved in patients during the first year after transplantation, regardless of immunosuppressive treatment. Our study suggests VirScan offers an unprecedented opportunity to screen and monitor posttransplant virus infection in a cost-effective, easy, and unbiased manner.

SARS-CoV-2 Associated Immune Dysregulation and COVID-Associated Pulmonary Aspergilliosis (CAPA): A Cautionary Tale.

As the global SARS-CoV-2 pandemic continues to plague healthcare systems, it has become clear that opportunistic pathogens cause a considerable proportion of SARS-CoV-2-associated mortality and morbidity cases. Of these, Covid-Associated Pulmonary Aspergilliosis (CAPA) is a major concern with evidence that it occurs in the absence of traditional risk factors such as neutropenia and is diagnostically challenging for the attending physician. In this review, we focus on the immunopathology of SARS-CoV-2 and how this potentiates CAPA through dysregulation of local and systemic immunity as well as the unintended consequences of approved COVID treatments including corticosteroids and IL-6 inhibitors. Finally, we will consider how knowledge of the above may aid in the diagnosis of CAPA using current diagnostics and what treatment should be instituted in probable and confirmed cases.

Evaluation of Abbott Architect, Siemens Immulite, bioMerieux Vidas, and Euroimmune assays for determination of Epstein-Barr virus serological diagnosis.

Serological tests detecting antibodies for Epstein-Barr virus (EBV) antigens are frequently used to define infection status. Several new automated assays are available for this purpose. We compared the performance of Architect, Immulite, Vidas, and Euroimmune immunofluorescence assays (IFA)/enzyme-linked immunosorbent assays (ELISA) for the detection of EBV viral capsid antigen (VCA) immunoglobulin M (IgM), VCA IgG, Epstein-Barr nuclear antigen (EBNA)-1 IgG. The routine diagnosis of EBV in our laboratory is done by anti-EBV VCA IgM IFT, anti-EBV VCA IgG IFT, and anti-EBNA-1 IgG ELISA (Euroimmune) Kits. Samples were tested with EBV Kits of Architect, Immulite, and Vidas for anti-VCA IgM, anti-VCA IgG, and anti-EBNA-1 IgG. The agreement between assays was calculated for each marker individually and for the determination of the EBV infection profile, based on the combination of three markers. BIOCHIP Sequence EBV (Avidity test) and/or EUROLINE EBV Profile 2 (IgG/IgM) were used as confirmatory assays to resolve discrepancies. The best concordance for VCA IgM detection was between Immulite and Vidas; for VCA IgG and EBNA-1 IgG were between Architect and Vidas. The sensitivities and specificities for VCA IgM were 97% and 88% for IFA, 100% and 94% for Architect, 100% and 99% for Vidas, and 100% and 100% for Immulite, respectively. The most problematic marker was EBNA-1 IgG with a 68.1% specificity by Immulite. Vidas panel had a perfect performance (100%) for determining all EBV profiles. Overall, evaluated assays had comparable performance. There were more discordant VCA IgG and EBNA-1 IgG results than VCA IgM results. The agreement between Architect and Vidas was better than other assays.

Diagnostic value of serological and molecular biological tests for infectious mononucleosis by EBV in different age stages and course of the disease.

Epstein-Barr virus (EBV)-based serologic antibody and viral nucleic acid assays have been found to be feasible means to diagnose infectious mononucleosis (IM) caused by EBV in children. In this study, we will further explore their diagnostic value for IM by EBV in different age stages and over the course of the disease. A collection of 616 children from clinically suspected IM cases was studied. Indirect immunofluorescence (IIF) for EBV-specific antibody (Euroimmun) combined with plasma EB viral nucleic acid assay (real-time fluorescence quantitative polymerase chain reaction reverse-transcription polymerase chain reaction) were used as reference methods. The diagnostic efficiency of the peripheral blood routine test, serologic antibody test, and plasma EB viral nucleic acid assay for the diagnosis of IM was evaluated, respectively. The sensitivity, specificity, Youden' index and the area under curve (AUC) were 93.08%, 87.77%, 0.81 and 0.904 (95% confidence interval [CI]: 0.878-0.931) for the peripheral lymphocyte test (lymphocytosis > 5 × 109 /L), 98.27%, 91.13%, 0.89 and 0.947 (95% CI: 0.927-0.967) for the plasma EBV-DNA test, and 84.08%, 96.33%, 0.80 and 0.902 (95% CI: 0.874-0.930) for the EBV viral capsid antigen (VCA)-IgG avidity test. The plasma EBV-DNA test has a higher diagnostic value than the VCA-IgG avidity test in children aged <6 years, especially aged <3 years; the peripheral lymphocyte test and plasma EBV-DNA test are suitable for the early stage of the disease, while the VCA-IgG avidity test for after 7 days of the disease. EBV antibody detection (IIF) should be combined with EBV nucleic acid detection in children age <6 years and the early stage of the disease.

SARS-CoV-2 antibody persistence in COVID-19 convalescent plasma donors: Dependency on assay format and applicability to serosurveillance.

BACKGROUND: Antibody response duration following severe acute respiratory syndrome coronavirus 2 infection tends to be variable and depends on severity of disease and method of detection. STUDY DESIGN AND METHODS: COVID-19 convalescent plasma from 18 donors was collected longitudinally for a maximum of 63-129 days following resolution of symptoms. All the samples were initially screened by the Ortho total Ig test to confirm positivity and subsequently tested with seven additional direct sandwich or indirect binding assays (Ortho, Roche, Abbott, Broad Institute) directed against a variety of antigen targets (S1, receptor binding domain, and nucleocapsid [NC]), along with two neutralization assays (Broad Institute live virus PRNT and Vitalant Research Institute [VRI] Pseudovirus reporter viral particle neutralization [RVPN]). RESULTS: The direct detection assays (Ortho total Ig total and Roche total Ig) showed increasing levels of antibodies over the time period, in contrast to the indirect IgG assays that showed a decline. Neutralization assays also demonstrated declining responses; the VRI RVPN pseudovirus had a greater rate of decline than the Broad PRNT live virus assay. DISCUSSION: These data show that in addition to variable individual responses and associations with disease severity, the detection assay chosen contributes to the heterogeneous results in antibody stability over time. Depending on the scope of the research, one assay may be preferable over another. For serosurveillance studies, direct, double Ag-sandwich assays appear to be the best choice due to their stability; in particular, algorithms that include both S1- and NC-based assays can help reduce the rate of false-positivity and discriminate between natural infection and vaccine-derived seroreactivity.

Production of high-quality SARS-CoV-2 antigens: Impact of bioprocess and storage on glycosylation, biophysical attributes, and ELISA serologic tests performance.

Serological assays are valuable tools to study SARS-CoV-2 spread and, importantly, to identify individuals that were already infected and would be potentially immune to a virus reinfection. SARS-CoV-2 Spike protein and its receptor binding domain (RBD) are the antigens with higher potential to develop SARS-CoV-2 serological assays. Moreover, structural studies of these antigens are key to understand the molecular basis for Spike interaction with angiotensin converting enzyme 2 receptor, hopefully enabling the development of COVID-19 therapeutics. Thus, it is urgent that significant amounts of this protein became available at the highest quality. In this study, we produced Spike and RBD in two human derived cell hosts: HEK293-E6 and Expi293F™. We evaluated the impact of different and scalable bioprocessing approaches on Spike and RBD production yields and, more importantly, on these antigens' quality attributes. Using negative and positive sera collected from human donors, we show an excellent performance of the produced antigens, assessed in serologic enzyme-linked immunosorbent assay (ELISA) tests, as denoted by the high specificity and sensitivity of the test. We show robust Spike productions with final yields of approx. 2 mg/L of culture that were maintained independently of the production scale or cell culture strategy. To the best of our knowledge, the final yield of 90 mg/L of culture obtained for RBD production, was the highest reported to date. An in-depth characterization of SARS-CoV-2 Spike and RBD proteins was performed, namely the antigen's oligomeric state, glycosylation profiles, and thermal stability during storage. The correlation of these quality attributes with ELISA performance show equivalent reactivity to SARS-CoV-2 positive serum, for all Spike and RBD produced, and for all storage conditions tested. Overall, we provide straightforward protocols to produce high-quality SARS-CoV-2 Spike and RBD antigens, that can be easily adapted to both academic and industrial settings; and integrate, for the first time, studies on the impact of bioprocess with an in-depth characterization of these proteins, correlating antigen's glycosylation and biophysical attributes to performance of COVID-19 serologic tests.

Development and application of a novel triplex protein microarray method for rapid detection of antibodies against avian influenza virus, Newcastle disease virus, and avian infectious bronchitis virus.

Avian influenza virus (AIV), Newcastle disease virus (NDV), and avian infectious bronchitis virus (IBV) inflict immense damage on the global poultry industry annually. Serological diagnostic methods are fundamental for the effective control and prevention of outbreaks caused by these viruses. In this study, a novel triplex protein microarray assay was developed and validated for the rapid and simultaneous visualized detection of antibodies against AIV, NDV, and IBV in chicken sera. The AIV nuclear protein (NP), NDV phosphoprotein (P), and IBV nonstructural protein 5 (nsp5) were produced in a prokaryotic expression system, purified, and immobilized onto an initiator integrated poly(dimethylsiloxane) (iPDMS) film as probes to detect antibodies against these viruses in chicken sera. After optimization of the reaction conditions, no cross-reactivity was detected with infectious bursal disease virus, avian leukosis virus subgroup J and chicken anemia virus antisera. The lowest detectable antibody titers in this assay corresponded to hemagglutination inhibition (HI) titers of 24 and 21 for AIV and NDV, respectively, and to an IDEXX antibody titer of 103 for IBV, using the HI assay and IDEXX commercial ELISA kit as the reference methods. When156 serum samples were tested using the new assay, the HI test and the IBV IDEXX ELISA kit, the assay showed 96.8% (151/156), 97.4% (152/156) and 99.4% (155/156) diagnostic accuracy for detection of AIV, NDV and IBV antibody, respectively. The current study suggests that the newly developed triplex microarray is rapid, sensitive, and specific, providing a viable alternative assay for AIV, NDV, and IBV antibody screening in epidemiological investigations and vaccination evaluations.

Identification of immunodominant proteins of Leishmania infantum by immunoproteomics to evaluate a recombinant multi-epitope designed antigen for serodiagnosis of human visceral leishmaniasis.

Visceral leishmaniasis (VL) is a protozoan disease caused by Leishmania infantum in the Mediterranean region including Iran. In 95% of cases, the disease can be fatal if not rapidly diagnosed and left untreated. We aimed to identify immunoreactive proteins of L. infantum (Iranian strain), and to design and evaluate a recombinant multi-epitope antigen for serodiagnosis of human VL. To detect the immunoreactive proteins of L. infantum promastigotes, 2DE immunoblotting technique was performed using different pooled sera of VL patients. The candidate immunoreactive proteins were identified using MALDI-TOF/TOF mass spectrophotometry. Among 125 immunoreactive spots detected in 2-DE gels, glucose-regulated protein 78 (GRP78), ubiquitin-conjugating enzyme E2, calreticulin, mitochondrial heat shock 70-related protein 1 (mtHSP70), heat shock protein 70-related protein, i/6 autoantigen-like protein, ATPase beta subunit, and proteasome alpha subunit 5 were identified. The potent epitopes from candidate immunodominant proteins including GRP78, mtHSP70 and ubiquitin-conjugating enzyme E2 were then selected to design a recombinant antigenic protein (GRP-UBI-HSP). The recombinant antigen was evaluated by ELISA and compared to direct agglutination test for detection of anti L. infantum human antibodies. We screened 34 sera of VL patients from endemic areas and 107 sera of individuals without L. infantum infection from non-endemic area of VL. The recombinant protein-based ELISA provided a sensitivity of 70.6% and a specificity of 84.1%. These results showed that GRP78, ubiquitin-conjugating enzyme E2, and mtHSP70 proteins are potential immunodominant targets of the host immune system in response to the parasite and they can be considered as potential candidate markers for diagnosis purposes.

COVIDIAGNOSTIX: health technology assessment of serological tests for SARS-CoV-2 infection.

OBJECTIVE: In vitro diagnostic tests for SARS-COV-2, also known as serological tests, have rapidly spread. However, to date, mostly single-center technical and diagnostic performance's assessments have been carried out without an intralaboratory validation process and a health technology assessment (HTA) systematic approach. Therefore, the rapid HTA for evaluating antibody tests for SARS-COV-2 was applied. METHODS: The use of rapid HTA is an opportunity to test innovative technology. Unlike traditional HTA (which evaluates the benefits of new technologies after being tested in clinical trials or have been applied in practice for some time), the rapid HTA is performed during the early stages of developing new technology. A multidisciplinary team conducted the rapid HTA following the HTA Core Model® (version 3.0) developed by the European Network for Health Technology Assessment. RESULTS: The three methodological and analytical steps used in the HTA applied to the evaluation of antibody tests for SARS-COV-2 are reported: the selection of the tests to be evaluated; the research and collection of information to support the adoption and appropriateness of the technology; and the preparation of the final reports and their dissemination. Finally, the rapid HTA of serological tests for SARS-CoV-2 is summarized in a report that allows its dissemination and communication. CONCLUSIONS: The rapid-HTA evaluation method, in addition to highlighting the characteristics that differentiate the tests from each other, guarantees a timely and appropriate evaluation, becoming a tool to create a direct link between science and health management.

Evaluation of Serological Tests for SARS-CoV-2: Implications for Serology Testing in a Low-Prevalence Setting.

BACKGROUND: Robust serological assays are essential for long-term control of the COVID-19 pandemic. Many recently released point-of-care (PoCT) serological assays have been distributed with little premarket validation. METHODS: Performance characteristics for 5 PoCT lateral flow devices approved for use in Australia were compared to a commercial enzyme immunoassay (ELISA) and a recently described novel surrogate virus neutralization test (sVNT). RESULTS: Sensitivities for PoCT ranged from 51.8% (95% confidence interval [CI], 43.1%-60.4%) to 67.9% (95% CI, 59.4%-75.6%), and specificities from 95.6% (95% CI, 89.2%-98.8%) to 100.0% (95% CI, 96.1%-100.0%). ELISA sensitivity for IgA or IgG detection was 67.9% (95% CI, 59.4%-75.6%), increasing to 93.8% (95% CI, 85.0%-98.3%) for samples >14 days post symptom onset. sVNT sensitivity was 60.9% (95% CI, 53.2%-68.4%), rising to 91.2% (95% CI, 81.8%-96.7%) for samples >14 days post symptom onset, with specificity 94.4% (95% CI, 89.2%-97.5%). CONCLUSIONS: Performance characteristics for COVID-19 serological assays were generally lower than those reported by manufacturers. Timing of specimen collection relative to onset of illness or infection is crucial in reporting of performance characteristics for COVID-19 serological assays. The optimal algorithm for implementing serological testing for COVID-19 remains to be determined, particularly in low-prevalence settings.

Clinical and Analytical Performance of an Automated Serological Test That Identifies S1/S2-Neutralizing IgG in COVID-19 Patients Semiquantitatively.

In the coronavirus (CoV) disease 2019 (COVID-19) pandemic, highly selective serological testing is essential to define exposure to severe acute respiratory syndrome CoV 2 (SARS-CoV-2). Many tests have been developed, yet with variable speeds to first results, and are of unknown quality, particularly when considering the prediction of neutralizing capacity. The LIAISON SARS-CoV-2 S1/S2 IgG assay was designed to measure antibodies against the SARS-CoV-2 native S1/S2 proteins in a standardized automated chemiluminescence assay. The clinical and analytical performances of the test were validated in an observational study using residual samples (>1,500) with a positive or negative COVID-19 diagnosis. The LIAISON SARS-CoV-2 S1/S2 IgG assay proved to be highly selective and specific and offered semiquantitative measures of serum or plasma levels of anti-S1/S2 IgG with neutralizing activity. The assay's diagnostic sensitivities were 91.3% and 95.7% at >5 or ≥15 days from diagnosis, respectively, and 100% when assessed against a neutralizing assay. The assay's specificity ranged between 97% and 98.5%. The average imprecision of the assay was a <5% coefficient of variation. Assay performance at 2 different cutoffs was evaluated to optimize predictive values. The automated LIAISON SARS-CoV-2 S1/S2 IgG assay brings efficient, sensitive, specific, and precise serological testing to the laboratory, with the capacity to test large amounts of samples per day; first results are available within 35 min, with a throughput of 170 tests/hour. The semiquantitative results provided by the test also associate with the presence of neutralizing antibodies and may provide a useful tool for the large-scale screening of convalescent-phase plasma for safe therapeutic use.

Serological antibody testing in the COVID-19 pandemic: their molecular basis and applications.

The ongoing COVID-19 pandemic has placed an overwhelming burden on the healthcare system, and caused major disruption to the world economy. COVID-19 is caused by SARS-CoV-2, a novel coronavirus that leads to a variety of symptoms in humans, including cough, fever and respiratory failure. SARS-CoV-2 infection can trigger extensive immune responses, including the production of antibodies. The detection of antibody response by serological testing provides a supplementary diagnostic tool to molecular tests. We hereby present a succinct yet comprehensive review on the antibody response to SARS-CoV-2 infection, as well as molecular mechanisms behind the strengths and limitations of serological antibody tests. The presence of antibodies can be detected in patient sera within days post symptom onset. Serological tests demonstrate superior sensitivity to molecular tests in some periods of time during disease development. Compared with the molecular tests, serological tests can be used for point-of-care testing, providing faster results at a lower cost. Commercially available serological tests show variable sensitivity and specificity, and the molecular basis of these variabilities are analysed. We discuss assays of different complexities that are used to specifically quantitate neutralising antibodies against SARS-CoV-2, which has important implications for vaccine development and herd immunity. Furthermore, we discuss examples of successful applications of serological tests to contact tracing and community-level sero-surveying, which provide invaluable information for pandemic management and assessment.

An exploration of the advantages of automated titration testing: low inter-instrument variability and equivalent accuracy for ABO and non-ABO antibody titres relative to tube testing.

BACKGROUND AND OBJECTIVES: Obtaining IgM and IgG titres is important in numerous clinical situations, including solid-organ transplant, obstetrics, and for testing of out-of-group plasma-containing components. Tube method is the most prevalent testing modality, though it is both labour-intensive and known for intra- and inter-laboratory variability. The utility of automated gel testing as a method to improve both inter- and intra-laboratory reproducibility is unknown. MATERIALS AND METHODS: Two academic centres participated in a study evaluating automated gel titreing. Group O plasma samples were used to measure titres of antibodies against ABO (IgM) with buffered gel cards and 4 minor and minor red-blood-cell antigens (IgG) anti-IgG gel cards. Multiple ORTHO VISION automated analyzers were used to assess inter-instrument variation. A subset of ABO (IgM) samples were compared between laboratories to evaluate inter-laboratory variability. Multiple samples were titred by tube and by automated gel technology to determine similarity of results. RESULTS: Testing demonstrated no significant difference between analysers or between sites when performing automated titrations (P ≥ 0·99). Non-ABO IgG titres were evaluated and demonstrated little inter-instrument variability. The IgM anti-A and -B titres obtained by automated gel testing were neither consistently higher nor lower than tube titres. Greater than 90% of titre values were within one dilution. CONCLUSION: Based on this study, our data suggest that titreing by automated gel testing is both highly reproducible (IgM and IgG) and does not differ significantly from manual tube testing results of direct agglutination (IgM).

Anti-platelet antibody immunoassays in childhood immune thrombocytopenia: a systematic review.

BACKGROUND: In adult immune thrombocytopenia (ITP), an acquired autoimmune bleeding disorder, anti-platelet autoantibody testing may be useful as a rule-in test. Childhood ITP has different disease characteristics, and the diagnostic and prognostic value of anti-platelet antibody testing remains uncertain. OBJECTIVE: To systematically review the diagnostic accuracy of anti-platelet autoantibody testing in childhood ITP. METHODS: PubMed and EMBASE were searched for studies evaluating immunoassays in childhood ITP. Study quality was assessed (QUADAS2), and evidence was synthesized descriptively. RESULTS: In total, 40 studies (1606 patients) were identified. Nine studies reported sufficient data to determine diagnostic accuracy measures. Anti-platelet IgG antibody testing showed a moderate sensitivity (0·36-0·80 platelet-associated IgG [direct test]; 0·19-0·39 circulating IgG [indirect test]). In studies that reported control data, including patients with non-immune thrombocytopenia, specificity was very good (0·80-1·00). Glycoprotein-specific immunoassays showed comparable sensitivity (three studies) and predominantly identified IgG anti-GP IIb/IIIa antibodies, with few IgG anti-GP Ib/IX antibodies. Anti-platelet IgM antibodies were identified in a substantial proportion of children (sensitivity 0·62-0·64 for direct and indirect tests). CONCLUSION: The diagnostic evaluation of IgG and IgM anti-platelet antibodies may be useful as a rule-in test for ITP. In children with insufficient platelets for a direct test, indirect tests may be performed instead. A negative test does not rule out the diagnosis of ITP. Future studies should evaluate the value of anti-platelet antibody tests in thrombocytopenic children with suspected ITP.

Evaluation of serological diagnostic tests of human brucellosis for prevention and control in Mexico.

Brucellosis is a zoonosis mainly present in developing countries. The WHO reports 500,000 new cases every year. From 2012 to 2016, 13,677 cases were reported in Mexico, with 2.00 to 2.64 rate per 100,000 inhabitants. To analyze the diagnostic algorithm of brucellosis in Mexico, we compared the commercial laboratory tests ELISA, Brucellacapt®, and lateral flow test (LFT) in a study of 473 individuals from two endemic Mexican populations. All patients were treated in first-level medical units for presenting brucellosis compatible symptoms and without a history of the disease. Clinical-epidemiological information was gathered and initial serum samples were obtained to react with anti-Brucella antibodies; subsequent samples were collected at follow-up treatment visits. Using the Rose Bengal screening, we found 165 negative samples and 308 positive reactive samples, of which 222 cases were confirmed and 234 were positive on at least one marker (IgG or IgM) or LFT. When Brucellacapt® was used, similar results to those observed with the conventional algorithm were found as judged by the Cohen's kappa coefficient (κ) (0.813, 95% CI 0.7788-0.8472). Similar κ indices between conventional algorithm and ELISA pair were found, 0.7038 (95% CI 0.6555-0.7521), representing high similarity between both groups of diagnosis. We conclude that conventional serodiagnoses, Brucellacapt® and LFT, presented inconclusive results and poor correlation between them. By contrast, ELISA test pair (IgG + IgM) presented high correlation with the conventional algorithm and greater capacity for correct positive and negative classification.

Immunosensor-based rapid quantitative detection of Newcastle disease virus antibodies using innovative gold immunochromatographic assay.

AIMS: A novel quantitative method for rapid Newcastle disease virus (NDV) antibody detection was developed based on an innovative gold immunochromatographic assay with a quantitative immunosensor. METHODS AND RESULTS: NDV antibody-detecting test strips containing a two-reaction system and double-test lines (T1, T2) were prepared. The test results were judged according to the signal ratio between the test and control lines as measured by the quantitative immunosensor. The minimum detection limit of the test strips for NDV antibodies was 22 titres. In addition, the assay was highly specific because only NDV antibodies produced visible test lines on the strip. The clinical application of the strips was tested by detecting NDV antibodies in 506 serum samples collected from chickens. The results showed a coincidence of 92·49% with those of the haemagglutination inhibition assay. CONCLUSIONS: The strips were successfully prepared and showed high specificity towards NDV, sensitivity and stability. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes a new method for detection of NDV antibody and provides a reference basis for rapid and quantitative monitoring of NDV antibodies. This new method overcomes the limitation of the existing colloidal gold immunochromatography, which only produces qualitative or semi-quantitative results.

Antibody tests for identification of current and past infection with SARS-CoV-2.

BACKGROUND: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and resulting COVID-19 pandemic present important diagnostic challenges. Several diagnostic strategies are available to identify current infection, rule out infection, identify people in need of care escalation, or to test for past infection and immune response. Serology tests to detect the presence of antibodies to SARS-CoV-2 aim to identify previous SARS-CoV-2 infection, and may help to confirm the presence of current infection. OBJECTIVES: To assess the diagnostic accuracy of antibody tests to determine if a person presenting in the community or in primary or secondary care has SARS-CoV-2 infection, or has previously had SARS-CoV-2 infection, and the accuracy of antibody tests for use in seroprevalence surveys. SEARCH METHODS: We undertook electronic searches in the Cochrane COVID-19 Study Register and the COVID-19 Living Evidence Database from the University of Bern, which is updated daily with published articles from PubMed and Embase and with preprints from medRxiv and bioRxiv. In addition, we checked repositories of COVID-19 publications. We did not apply any language restrictions. We conducted searches for this review iteration up to 27 April 2020. SELECTION CRITERIA: We included test accuracy studies of any design that evaluated antibody tests (including enzyme-linked immunosorbent assays, chemiluminescence immunoassays, and lateral flow assays) in people suspected of current or previous SARS-CoV-2 infection, or where tests were used to screen for infection. We also included studies of people either known to have, or not to have SARS-CoV-2 infection. We included all reference standards to define the presence or absence of SARS-CoV-2 (including reverse transcription polymerase chain reaction tests (RT-PCR) and clinical diagnostic criteria). DATA COLLECTION AND ANALYSIS: We assessed possible bias and applicability of the studies using the QUADAS-2 tool. We extracted 2x2 contingency table data and present sensitivity and specificity for each antibody (or combination of antibodies) using paired forest plots. We pooled data using random-effects logistic regression where appropriate, stratifying by time since post-symptom onset. We tabulated available data by test manufacturer. We have presented uncertainty in estimates of sensitivity and specificity using 95% confidence intervals (CIs). MAIN RESULTS: We included 57 publications reporting on a total of 54 study cohorts with 15,976 samples, of which 8526 were from cases of SARS-CoV-2 infection. Studies were conducted in Asia (n = 38), Europe (n = 15), and the USA and China (n = 1). We identified data from 25 commercial tests and numerous in-house assays, a small fraction of the 279 antibody assays listed by the Foundation for Innovative Diagnostics. More than half (n = 28) of the studies included were only available as preprints. We had concerns about risk of bias and applicability. Common issues were use of multi-group designs (n = 29), inclusion of only COVID-19 cases (n = 19), lack of blinding of the index test (n = 49) and reference standard (n = 29), differential verification (n = 22), and the lack of clarity about participant numbers, characteristics and study exclusions (n = 47). Most studies (n = 44) only included people hospitalised due to suspected or confirmed COVID-19 infection. There were no studies exclusively in asymptomatic participants. Two-thirds of the studies (n = 33) defined COVID-19 cases based on RT-PCR results alone, ignoring the potential for false-negative RT-PCR results. We observed evidence of selective publication of study findings through omission of the identity of tests (n = 5). We observed substantial heterogeneity in sensitivities of IgA, IgM and IgG antibodies, or combinations thereof, for results aggregated across different time periods post-symptom onset (range 0% to 100% for all target antibodies). We thus based the main results of the review on the 38 studies that stratified results by time since symptom onset. The numbers of individuals contributing data within each study each week are small and are usually not based on tracking the same groups of patients over time. Pooled results for IgG, IgM, IgA, total antibodies and IgG/IgM all showed low sensitivity during the first week since onset of symptoms (all less than 30.1%), rising in the second week and reaching their highest values in the third week. The combination of IgG/IgM had a sensitivity of 30.1% (95% CI 21.4 to 40.7) for 1 to 7 days, 72.2% (95% CI 63.5 to 79.5) for 8 to 14 days, 91.4% (95% CI 87.0 to 94.4) for 15 to 21 days. Estimates of accuracy beyond three weeks are based on smaller sample sizes and fewer studies. For 21 to 35 days, pooled sensitivities for IgG/IgM were 96.0% (95% CI 90.6 to 98.3). There are insufficient studies to estimate sensitivity of tests beyond 35 days post-symptom onset. Summary specificities (provided in 35 studies) exceeded 98% for all target antibodies with confidence intervals no more than 2 percentage points wide. False-positive results were more common where COVID-19 had been suspected and ruled out, but numbers were small and the difference was within the range expected by chance. Assuming a prevalence of 50%, a value considered possible in healthcare workers who have suffered respiratory symptoms, we would anticipate that 43 (28 to 65) would be missed and 7 (3 to 14) would be falsely positive in 1000 people undergoing IgG/IgM testing at days 15 to 21 post-symptom onset. At a prevalence of 20%, a likely value in surveys in high-risk settings, 17 (11 to 26) would be missed per 1000 people tested and 10 (5 to 22) would be falsely positive. At a lower prevalence of 5%, a likely value in national surveys, 4 (3 to 7) would be missed per 1000 tested, and 12 (6 to 27) would be falsely positive. Analyses showed small differences in sensitivity between assay type, but methodological concerns and sparse data prevent comparisons between test brands. AUTHORS' CONCLUSIONS: The sensitivity of antibody tests is too low in the first week since symptom onset to have a primary role for the diagnosis of COVID-19, but they may still have a role complementing other testing in individuals presenting later, when RT-PCR tests are negative, or are not done. Antibody tests are likely to have a useful role for detecting previous SARS-CoV-2 infection if used 15 or more days after the onset of symptoms. However, the duration of antibody rises is currently unknown, and we found very little data beyond 35 days post-symptom onset. We are therefore uncertain about the utility of these tests for seroprevalence surveys for public health management purposes. Concerns about high risk of bias and applicability make it likely that the accuracy of tests when used in clinical care will be lower than reported in the included studies. Sensitivity has mainly been evaluated in hospitalised patients, so it is unclear whether the tests are able to detect lower antibody levels likely seen with milder and asymptomatic COVID-19 disease. The design, execution and reporting of studies of the accuracy of COVID-19 tests requires considerable improvement. Studies must report data on sensitivity disaggregated by time since onset of symptoms. COVID-19-positive cases who are RT-PCR-negative should be included as well as those confirmed RT-PCR, in accordance with the World Health Organization (WHO) and China National Health Commission of the People's Republic of China (CDC) case definitions. We were only able to obtain data from a small proportion of available tests, and action is needed to ensure that all results of test evaluations are available in the public domain to prevent selective reporting. This is a fast-moving field and we plan ongoing updates of this living systematic review.