Diagnostic performance of the fully automated Roche Elecsys SARS-CoV-2 antigen electrochemiluminescence immunoassay: a pooled analysis

Evaluation of three alternative methods to the plaque reduction neutralizing assay for measuring neutralizing antibodies to dengue virus serotype 2

BACKGROUND

Dengue is a global public health challenge which requires accurate diagnostic methods for surveillance and control. The gold standard for detecting dengue neutralizing antibodies (nAbs) is the plaque reduction neutralization test (PRNT), which is both labor-intensive and time-consuming. This study aims to evaluate three alternative approaches, namely, the MTT-based (or (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) microneutralization assay, the xCELLigence real-time cell analysis (RTCA), and the immuno-plaque assay-focus reduction neutralization test (iPA-FRNT).

METHODS

Twenty-two residual serum samples were tested for DENV-2 nAbs using all four assays at three neutralization endpoints of 50%, 70% and 90% inhibition in virus growth. For each neutralization endpoint, results were compared using linear regression and correlation analyses. Test performance characteristics were further obtained for iPA-FRNT using 38 additional serum samples.

RESULTS

Positive correlation of DENV-2 neutralization titers for the MTT-based microneutralization assay and the PRNT assay was only observed at the neutralization endpoint of 50% (r = 0.690). In contrast, at all three neutralization end points, a linear trend and positive correlation of DENV-2 neutralization titers for the xCELLigence RTCA and the PRNT assays were observed, yielding strong or very strong correlation (r = 0.829 to 0.967). This was similarly observed for the iPA-FRNT assay (r = 0.821 to 0.916), which also offered the added advantage of measuring neutralizing titers to non-plaque forming viruses.

CONCLUSION

The xCELLigence RTCA and iPA-FRNT assays could serve as suitable alternatives to PRNT for dengue serological testing. The decision to adopt these methods may depend on the laboratory setting, and the utility of additional applications offered by these technologies.

High-Sensitivity Homogeneous Detection of miRNA-155 Governed by DNA Walker-Regulated Surface DNA Density of Magnetic Electrochemiluminescence Nanoparticles

Homogeneous electrochemiluminescence (ECL) has gained attention for its simplicity and stability. However, false positives due to solution background interference pose a challenge. To address this, magnetic ECL nanoparticles (Fe3O4@Ru@SiO2 NPs) were synthesized, offering easy modification, magnetic separation, and stable luminescence. These were utilized in an ECL sensor for miRNA-155 (miR-155) detection, with locked DNAzyme and substrate chain (mDNA) modified on their surface. The poor conductivity of long-chain DNA significantly impacts the conductivity and electron transfer capability of Fe3O4@Ru@SiO2 NPs, resulting in weaker ECL signals. Upon target presence, unlocked DNAzyme catalyzes mDNA cleavage, leading to shortened DNA chains and reduced density. In contrast, the presence of short-chain DNA has minimal impact on the conductivity and electron transfer capability of Fe3O4@Ru@SiO2 NPs. Simultaneously, the material surface's electronegativity decreases, weakening the electrostatic repulsion with the negatively charged electrode, resulting in the system detecting stronger ECL signals. This sensor enables homogeneous ECL detection while mitigating solution background interference through magnetic separation. Within a range of 100 fM to 10 nM, the sensor exhibits a linear relationship between ECL intensity and target concentration, with a 26.91 fM detection limit. It demonstrates high accuracy in clinical sample detection, holding significant potential for clinical diagnostics. Future integration with innovative detection strategies may further enhance sensitivity and specificity in biosensing applications.

Diagnostic accuracy of Siemens SARS-CoV-2 Antigen (CoV2Ag) chemiluminescent immunoassay for diagnosing acute SARS-CoV-2 infection: a pooled analysis

BACKGROUND

This article provides a critical literature review and pooled analysis of diagnostic accuracy of the fully-automated Siemens SARS-CoV-2 Antigen (CoV2Ag) chemiluminescent immunoassay for diagnosis of acute SARS-CoV-2 infections.

METHODS

An electronic search was conducted in Scopus, PubMed and medRxiv using the keywords ["Siemens AND CoV2Ag"] OR ["Siemens AND SARS-CoV-2 AND antigen"] for capturing studies that investigated the accuracy of Siemens CoV2Ag for diagnosing acute SARS-CoV-2 infection against a reference SARS-CoV-2 molecular test. The retrieved information was used for constructing a 2 × 2 table and for calculating pooled diagnostic sensitivity, specificity, Summary Receiver Operating Characteristic Curve (SROC) and Agreement. This study followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting checklist.

RESULTS

Four studies totalling 1,310 respiratory samples (612 with high viral load) were finally included in our analysis. The cumulative area under the curve, accuracy, sensitivity, specificity, were 0.964 (95% CI, 0.957-0.971), 86.9% (95% CI, 84.9-88.7%), 0.79 (95% CI, 0.76-0.82) and 0.98 (95% CI, 0.96-0.99), respectively. The negative (NPV) and positive (PPV) predictive values were 0.77 (0.74-0.79) and 0.98 (95% CI, 0.96-99), respectively. The diagnostic sensitivity in samples with high viral load (i.e., Ct<29-30) was 0.95 (95% CI, 0.93-0.97).

CONCLUSIONS

The Siemens CoV2Ag fully-automated and high-throughput immunoassay approximates the minimum performance criteria for general SARS-CoV-2 antigen testing and displays excellent performance in samples with high viral load, thus representing a valuable screening solution for risk assessment in COVID-19 and for limiting viral spread.

Evaluation of four laboratory-based high-throughput SARS-CoV-2 automated antigen tests compared to RT-PCR on nasal and oropharyngeal samples

BACKGROUND

The demand for RT-PCR testing has been unprecedented during the SARS-CoV-2 pandemic. Fully automated antigen tests (AAT) are less cumbersome than RT-PCR, but data on performance compared to RT-PCR are scarce.

METHODS

The study consists of two parts. A retrospective analytical part, comparing the performance of four different AAT on 100 negative and 204 RT-PCR positive deep oropharyngeal samples divided into four groups based on RT-PCR cycle of quantification levels. In the prospective clinical part, 206 individuals positive for and 199 individuals negative for SARS-CoV-2 were sampled from either the anterior nasal cavity (mid-turbinate) or by deep oropharyngeal swabs or both. The performance of AATs was compared to RT-PCR.

RESULTS

The overall analytical sensitivity of the AATs differed significantly from 42% (95% CI 35-49) to 60% (95% CI 53-67) with 100% analytical specificity. Clinical sensitivity of the AATs differed significantly from 26% (95% CI 20-32) to 88% (95% CI 84-93) with significant higher sensitivity for mid-turbinate nasal swabs compared to deep oropharyngeal swabs. Clinical specificity varied from 97% to 100%.

CONCLUSION

All AATs were highly specific for detection of SARS-CoV-2. Three of the four AATs were significantly more sensitive than the fourth AAT both in terms of analytical and clinical sensitivity. Anatomical test location significantly influenced the clinical sensitivity of AATs.

Real-world assessment of the clinical performance of COVID-VIRO ALL IN rapid SARS-CoV-2 antigen test

OBJECTIVES

Since the external validation of severe acute respiratory syndrome coronavirus 2 antigen rapid diagnostic tests (SARS-CoV-2 RDT-Ags) is a necessary requisite before they can be introduced into routine clinical practice, this study reports the results of a real-world assessment of the clinical performance of the new COVID-VIRO ALL IN device.

METHODS

The study population consisted in 165 outpatients (median age: 43 years, range: 14-68 years; 66.1% females) who had paired nasal and nasopharyngeal samples collected upon hospital presentation. The samples were concomitantly tested with the AAZ-LMB COVID-VIRO ALL IN SARS-CoV-2 RDT-Ag and with Cepheid Xpert Xpress SARS-CoV-2 real-time reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

The number of subjects with positive RT-PCR results (i.e., mean Ct value <45) was 116 (70.3%), 109 (66.1%) and 86 (52.1%) with mean Ct values <37 and <30, respectively. In all RT-PCR positive samples, COVID-VIRO ALL IN displayed 78.8% agreement, 0.698 sensitivity, 1.000 specificity, 0.583 negative predictive value (NPV) and 1.000 positive predictive value (PPV) compared to RT-PCR. The median Ct value of samples testing positive with COVID-VIRO ALL IN was significantly lower than those testing negative (22.8 vs. 32.2; p<0.001). In samples with high viral load (i.e., Ct value <30), COVID-VIRO ALL IN displayed 92.1% agreement, 0.895 sensitivity, 0.949 specificity, 0.983 NPV and 0.951 PPV compared to RT-PCR.

CONCLUSIONS

Although the diagnostic performance of COVID-VIRO ALL IN do not exactly match those of the manufacturer, its high NPV in high viral load samples would enable fast-track and rapid identification of highly contagious subjects.

Tutorial: statistical methods for the meta-analysis of diagnostic test accuracy studies

This tutorial shows how to perform a meta-analysis of diagnostic test accuracy studies (DTA) based on a 2 × 2 table available for each included primary study. First, univariate methods for meta-analysis of sensitivity and specificity are presented. Then the use of univariate logistic regression models with and without random effects for e.g. sensitivity is described. Diagnostic odds ratios (DOR) are then introduced to combine sensitivity and specificity into one single measure and to assess publication bias. Finally, bivariate random effects models using the exact binomial likelihood to describe within-study variability and a normal distribution to describe between-study variability are presented as the method of choice. Based on this model summary receiver operating characteristic (sROC) curves are constructed using a regression model logit-true positive rate (TPR) over logit-false positive rate (FPR). Also it is demonstrated how to perform the necessary calculations with the freely available software R. As an example a meta-analysis of DTA studies using Procalcitonin as a diagnostic marker for sepsis is presented.

Clinical Chemistry and Laboratory Medicine celebrates 60 years – narrative review devoted to the contribution of the journal to the diagnosis of SARS-CoV-2

This review is an integral part of the special issue for the 60 years of the journal Clinical Chemistry and Laboratory Medicine (CCLM). The aim of the review is to highlight the role of the clinical laboratory since the emergence of the “severe acute respiratory syndrome coronavirus 2” (SARS-CoV-2), which causes Coronavirus disease 2019 (COVID-19), with special focus on the contribution of the journal in generating knowledge in SARS-CoV-2 diagnosis. As of October 30, 2022, a total of 186 CCLM publications were dedicated to COVID-19. Of importance, major International Federation of Clinical Chemistry (IFCC) guidelines related to the diagnosis of COVID-19 were published in CCLM. Between early-2020 and late October 2022, COVID-19 publications represented around 27% of all articles in CCLM, highlighting the willingness of the editorial board to help the field in order to better describe and diagnose this new emerging disease. First launched in 1963 under the name “Zeitschrift für Klinische Chemie”, the Journal was entirely devoted to clinical chemistry in the strict sense. The various topics published in relation to COVID-19 including its diagnosis, its impact on biochemical or hematological measures, as well as biosafety measures, is the perfect example that shows that the journal has greatly diversified over time.

Evaluating the role of a fully automated SARS-CoV-2 antigen ECLIA immunoassay in the management of the SARS COV 2 pandemic on general population

OBJECTIVES

Chemiluminescence immunoassay (CLIA) automated assays (fourth-generation antigen test) for SARS-CoV-2 detection are promising because of their analytical productivity, but have lower sensitivity and specificity than rt-PCR assays. The authors of this paper evaluated a recent immunoassay implemented on Siemens Atellica IM, investigating how much this could affect the actual feasibility of this diagnostic during the pandemic.

METHODS

From the three-day routine 134 positive and 241 negative swab samples by rt-PCR test were evaluated, selected as 1/3 positive - 2/3 negative.

RESULTS

Using rt-PCR as gold standard, the specificity of immunoassay was 96.7%, while sensitivity was 68.0%. Sensitivity is inversely proportional to the viral load: 100% for cycles threshold (CT) values from 14 to 29, 95% until 30 CT, then 85, 74, 72, 68%, for 31-35 CT respectively.

CONCLUSIONS

Our study confirms the reliability of the fourth-generation antigen assay in recognizing negative samples. Conversely, sensitivity appears to be less reliable (68.0%) than reported in the literature. This could be due to a non-randomized study group: many swab samples were taken from patients with expected low viral load (hospitalized for COVID for more than 10-12 days or asymptomatic patients for epidemiological surveillance). The strong correlation of sensitivity and viral load could prove significant to track the infectiousness of infected people, as previous studies reported that a viral load of at least 10E6 copies of RNA/mL, corresponding to 25 CT, is the threshold of transmission of the disease.

Evaluation of a laboratory-based high-throughput SARS-CoV-2 antigen assay

OBJECTIVES

Antigen tests are an essential part of SARS-CoV-2 testing strategies. Rapid antigen tests are easy to use but less sensitive compared to nucleic acid amplification tests (NAT) and less suitable for large-scale testing. In contrast, laboratory-based antigen tests are suitable for high-throughput immunoanalyzers. Here we evaluated the diagnostic performance of the laboratory-based Siemens Healthineers SARS-CoV-2 Antigen (CoV2Ag) assay.

METHODS

In a public test center, from 447 individuals anterior nasal swab specimens as well as nasopharyngeal swab specimens were collected. The nasal swab specimens were collected in sample inactivation medium and measured using the CoV2Ag assay. The nasopharyngeal swab specimens were measured by RT-PCR. Additionally, 9,046 swab specimens obtained for screening purposes in a tertiary care hospital were analyzed and positive CoV2Ag results confirmed by NAT.

RESULTS

In total, 234/447 (52.3%) participants of the public test center were positive for SARS-CoV-2-RNA. Viral lineage B1.1.529 was dominant during the study. Sensitivity and specificity of the CoV2Ag assay were 88.5% (95%CI: 83.7-91.9%) and 99.5% (97.4-99.9%), respectively. Sensitivity increased to 93.7% (97.4-99.9%) and 98.7% (97.4-99.9%) for swab specimens with cycle threshold values <30 and <25, respectively. Out of 9,046 CoV2Ag screening tests from hospitalized patients, 21 (0.2%) swab specimens were determined as false-positive by confirmatory NAT.

CONCLUSIONS

Using sample tubes containing inactivation medium the laboratory-based high-throughput CoV2Ag assay is a very specific and highly sensitive assay for detection of SARS-CoV-2 antigen in nasal swab specimens including the B1.1.529 variant. In low prevalence settings confirmation of positive CoV2Ag results by SARS-CoV-2-RNA testing is recommended.

Ad interim recommendations for diagnosing SARS-CoV-2 infection by the IFCC SARS-CoV-2 variants working group

This document, endorsed by the IFCC Working Group on SARS-CoV-2 Variants, aims to update previous indications for diagnosing acute SARS-CoV-2 infection, taking into consideration the evidence that has emerged after the origin and spread of new lineages and sub-lineages of the virus characterized by mutated genetics and altered biochemical, biological and clinical characteristics. These indications encompass the use of different diagnostic strategies in specific clinical settings, such as high risk of SARS-CoV-2 infection (symptomatic patients), low risk of SARS-CoV-2 infection (asymptomatic subjects) at hospital admission/contact tracing, testing in asymptomatic subjects, in epidemiologic surveys and/or population screening, along with tentative indications for identification of new lineages and/or sub-lineages of SARS-CoV-2.

LumiraDX SARS-CoV-2 Antigen Test for Diagnosing Acute SARS-CoV-2 Infection: Critical Literature Review and Meta-Analysis

We present here a critical literature review and meta-analysis on the accuracy of the LumiraDX SARS-CoV-2 Antigen Test for diagnosing acute SARS-CoV-2 infection. An electronic search was conducted in the Scopus and Medline databases using the keywords “LumiraDX” AND “COVID-19” OR “SARS-CoV-2”, without date (i.e., up to 1 February 2022) or language restrictions, for detecting clinical studies where the diagnostic accuracy of the LumiraDX SARS-CoV-2 Antigen Test was compared with reference molecular diagnostic methods. All studies where the rates of true positive, true negative, false positive and false negative cases were available for constructing a 2 × 2 table and providing pooled estimates of diagnostic sensitivity, specificity and accuracy were included in a pooled analysis. The study was conducted in accordance with the PRISMA (preferred reporting items for systematic reviews and meta-analyses) reporting checklist. Eleven studies (n = 8527 samples) could be included in our pooled analysis, while five additional documents provided diagnostic accuracy data but could not be extracted for construction of a 2 × 2 table. The pooled diagnostic sensitivity and specificity were 0.86 (95%CI, 0.84–0.88) and 0.99 (95%CI, 0.98–0.99), respectively, while the area under the summary receiver operating characteristic curve was 0.974 (95%CI, 0.965–0.983) and the agreement was 96.8% (95%CI, 96.4–97.1%), with kappa statistics of 0.87 (95%CI, 0.85–0.88). In conclusion, the diagnostic performance of the LumiraDX SARS-CoV-2 Antigen Test would allow the conclusion that it may be seen as a reliable alternative to molecular testing for the rapid preliminary screening of acute SARS-CoV-2 infections.

Fujirebio Lumipulse SARS-CoV-2 antigen immunoassay: pooled analysis of diagnostic accuracy

We provide here a pooled analysis of accuracy of Fujirebio Lumipulse SARS-CoV-2 Antigen chemiluminescent immunoassay for diagnosing acute SARS-CoV-2 infections. An electronic search was conducted in Scopus and Medline with the keywords "Lumipulse" AND "antigen" AND "SARS-CoV-2" or "COVID-19", up to January 21, 2022, for identifying clinical investigations (minimum sample size ≥100) where diagnostic accuracy of Lumipulse G SARS-CoV-2 Ag was tested against reference molecular techniques. All studies which allowed to construct a 2 × 2 table were included in a pooled analysis. A final number of 21 studies, totalling 17,648 nasopharyngeal and 8538 saliva specimens, were finally included. The pooled diagnostic sensitivity and specificity in nasopharyngeal swabs were 0.80 (95%CI, 0.78-0.81) and 0.98 (95%CI, 0.97-0.98), respectively, whilst the area under the curve and agreement were 0.980 (95%CI, 0.973-0.986) and 94.9%, respectively. In the twelve studies which used the fixed 1.34 pg/mL currently recommended manufacturer's threshold, the diagnostic accuracy remained unvaried. In saliva samples, the pooled diagnostic sensitivity and specificity were 0.75 (95%CI, 0.36-0.62) and 1.00 (95%CI, 0.99-1.00), respectively, whilst the area under the curve and were 0.976 (95%CI, 0.969-0.984) and 98.4%, respectively. In the five studies which used the fixed 0.67 pg/mL currently recommended manufacturer's threshold, the diagnostic accuracy remained unvaried. In conclusion, Lumipulse G SARS-CoV-2 Ag assay demonstrates good diagnostic sensitivity and specificity, thus representing a valuable complementary and integrative option to molecular testing for SARS-CoV-2 in the current pandemic.

Critical literature review and pooled analysis of diagnostic accuracy of Ortho VITROS SARS-CoV-2 antigen test for diagnosing acute SARS-CoV-2 infections

Background: The present study is aimed at reviewing and meta-analyzing the currently published data on the diagnostic accuracy of Ortho VITROS SARS-CoV-2 antigen test for diagnosing acute SARS-CoV-2 infections. Methods: An electronic search was conducted in Scopus and Medline with the keywords "VITROS" AND "antigen" AND "COVID-19" OR "SARS-CoV-2" AND "immunoassay" within the search fields "TITLE" AND "ABSTRACT" AND "KEYWORDS", without no date (i.e., up to January 23, 2022) or language restrictions, aimed at detecting documents reporting the diagnostic accuracy of this SARSCoV-2 immunoassay compared with reference molecular diagnostic methods. Results: Overall, 5 studies (n=2734 samples) were finally included in our pooled analysis, four of which also provided diagnostic sensitivity in oro-and nasopharyngeal samples with high viral load. The pooled cumulative diagnostic sensitivity and specificity were 0.82 (95%CI, 0.78-0.86) and 1.00 (95%CI, 1.00-1.00), respectively, whilst the area under the curve was 0.995 (95%CI, 0.993-0.997), the cumulative agreement 97.2% (95%CI, 96.5-97.8%), with 0.89 (95%CI, 0.86-0.91) kappa statistics, thus reflecting an almost perfect concordance with reference molecular biology techniques. The pooled diagnostic sensitivity in samples with high viral load was as high as 0.98 (95%CI, 0.96-0.99). Conclusions: These results confirm that the automated and high-throughput Ortho VITROS SARS-CoV-2 antigen test may represent a valuable surrogate of molecular testing for diagnosing acute SARS-CoV-2 infections, especially in subjects with high viral load.