Performance Characteristics of the Vidas SARS-CoV-2 IgM and IgG Serological Assays.

The COVID-19 pandemic, caused by the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread worldwide. Serological testing for SARS-CoV-2-specific antibodies plays an important role in understanding and controlling the pandemic, notably through epidemiological surveillance. Well-validated and highly specific SARS-CoV-2 serological assays are urgently needed. We describe here the analytical and clinical performance of Vidas SARS-CoV-2 IgM and Vidas SARS-CoV-2 IgG, two CE-marked, emergency use authorization (EUA)-authorized, automated, qualitative assays for the detection of SARS-CoV-2-specific IgM and IgG, respectively. Both assays showed high within-run and within-laboratory precision (coefficients of variation < 11.0%) and very low cross-reactivity toward sera of patients with a past common coronavirus or respiratory virus infection. Clinical specificity determined on up to 989 prepandemic healthy donors was ≥99% with a narrow 95% confidence interval for both IgM and IgG assays. Clinical sensitivity was determined on up to 232 samples from 130 reverse transcriptase PCR (RT-PCR)-confirmed SARS-CoV-2 patients. The positive percent agreement (PPA) with SARS-CoV-2 PCR reached 100% at ≥16 days (Vidas SARS-CoV-2 IgM) and ≥32 days (Vidas SARS-CoV-2 IgG) of symptom onset. Combined IgM/IgG test results improved the PPA compared to each test alone. SARS-CoV-2 IgG seroconversion followed closely that of SARS-CoV-2 IgM and remained stable over time, while SARS-CoV-2 IgM levels rapidly declined. Interestingly, SARS-CoV-2-specific IgM and IgG responses were significantly higher in COVID-19 hospitalized versus nonhospitalized patients. Altogether, the Vidas SARS-CoV-2 IgM and IgG assays are highly specific and sensitive serological tests suitable for the reliable detection of past acute SARS-CoV-2 infections.

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.

Measurement of S100B protein: evaluation of a new prototype on a bioMérieux Vidas® 3 analyzer.

Background The addition of S100B protein to guidelines for the management of mild traumatic brain injury (mTBI) decreases the amount of unnecessary computed tomography (CT) scans with a significant decrease in radiation exposure and an increase in cost savings. Both DiaSorin and Roche Diagnostics have developed automated assays for S100B determination. Recently, bioMérieux developed a prototype immunoassay for serum S100B determination. For the first time, we present the evaluation of the S100B measurement using a bioMérieux Vidas® 3 analyzer. Methods We evaluated the matrix effects of serum and plasma, and their stability after storage at 2-8 °C, -20 °C and -80 °C. The new measurement prototype (bioMérieux) was compared with an established one (Roche Diagnostics), and a precision study was also conducted. Lastly, clinical diagnostics performance of the bioMérieux and Roche Diagnostics methods were compared for 80 patients referred to the Emergency Department for mTBI. Results Stability after storage at 2-8 °C, -20 °C, and -80 °C and validation of the serum matrix were demonstrated. The bioMérieux analyzer was compared to the Roche Diagnostics system, and the analytical precision was found to be efficient. Clinical diagnosis performance evaluation confirmed the predictive negative value of S100B in the management of mTBI. Conclusions The study's data are useful for interpreting serum S100B results on a bioMérieux Vidas® 3 analyzer.

Salmonella prevalence and serovar distribution in healthy slaughter sheep and cattle determined by ISO 6579 and VIDAS UP Salmonella methods.

Prevalence of Salmonella in slaughter sheep and cattle was determined by International Organization for Standardization Method 6579 (ISO) and Vitek Immunodiagnostic Assay System UP Salmonella Phage Technology (VIDAS UP Salmonella SPT-VIDAS UP). A total of 400 healthy slaughter sheep (n = 200) and cattle (n = 200) carcass (C), fecal content (FC), mesenteric lymph node (MLN), liver (L), kidney (K), spleen (S) and gall bladder (GB) were randomly sampled and analysed. ISO and VIDAS UP results indicated 13 (3.25%) and 17 (4.25%) of 400 animals carried Salmonella, respectively, regardless of sample type. There was no isolation from L, S, GB, while 2 C (0.5%), 6 FC (1.5%), 7 MLN (1.75%), 3 K (0.75%) were contaminated with Salmonella. S. Typhimurium (27.8%), S. Enteritidis (22.2%), S. Newport (22.2%) were the three dominant serovars, followed by S. Kentucky (11.1%), S. Umbilo (5.6%), S. Corvallis (5.6%), and S. Albany (5.6%). Overall prevalence in 2800 samples was 0.46% by ISO and 0.61% by VIDAS UP. High relative trueness (RT: 99.79%) of VIDAS UP with a substantial agreement to ISO (κ value: 0.80) indicated its efficiency to accompany ISO to monitor Salmonella in slaughter animals. As the first report to evaluate ISO and VIDAS UP in detecting Salmonella from slaughter sheep and cattle, this current prevalence signifies a risk for public health in red-meat and related products in Turkey.

Evaluation of bioMérieux's Dissociated Vidas Lyme IgM II and IgG II as a First-Tier Diagnostic Assay for Lyme Disease.

The recommended laboratory diagnostic approach for Lyme disease is a standard two-tiered testing (STTT) algorithm where the first tier is typically an enzyme immunoassay (EIA) that if positive or equivocal is reflexed to Western immunoblotting as the second tier. bioMérieux manufactures one of the most commonly used first-tier EIAs in the United States, the combined IgM/IgG Vidas test (LYT). Recently, bioMérieux launched its dissociated first-tier tests, the Vidas Lyme IgM II (LYM) and IgG II (LYG) EIAs, which use purified recombinant test antigens and a different algorithm than STTT. The dissociated LYM/LYG EIAs were evaluated against the combined LYT EIA using samples from 471 well-characterized Lyme patients and controls. Statistical analyses were conducted to assess the performance of these EIAs as first-tier tests and when used in two-tiered algorithms, including a modified two-tiered testing (MTTT) approach where the second-tier test was a C6 EIA. Similar sensitivities and specificities were obtained for the two testing strategies (LYT versus LYM/LYG) when used as first-tier tests (sensitivity, 83 to 85%; specificity, 85 to 88%) with an observed agreement of 80%. Sensitivities of 68 to 69% and 76 to 77% and specificities of 97% and 98 to 99% resulted when the two EIA strategies were followed by Western immunoblotting and when used in an MTTT, respectively. The MTTT approach resulted in significantly higher sensitivities than did STTT. Overall, the LYM/LYG EIAs performed equivalently to the LYT EIA in test-to-test comparisons or as first-tier assays in STTT or MTTT with few exceptions.

New AMH assay allows rapid point of care measurements of ovarian reserve.

In this study, we compare two commercial automated immunoassays used to evaluate serum anti-Müllerian hormone (AMH) levels as a prognostic value for ovarian response and pregnancy outcome in assisted reproductive technology cycles. Serum AMH was measured for 193 women. We performed a simultaneous measurement in serum AMH with the two alternative kits VIDAS® and Elecsys® AMH assay. For all women undergoing in vitro fertilization cycle, we collected data on their antral follicle count (AFC) and numbers of retrieved cumulus oocyte complexes (OC) and metaphase II oocytes and pregnancy outcome. The AMH values provided by VIDAS® were correlated with the values obtained with Elecsys® (0.977 for fresh and 0.971 for the frozen samples). For both assays AMH exhibited a moderate positive correlation with AFC, OC and MII oocytes (0.612, 0.674, 0.605 for VIDAS® and 0.570, 0.617, 0.530 for Elecsys®, respectively). AMH prediction of biochemical and clinical pregnancy was similar. The present results suggest that the VIDAS® AMH assay is broadly comparable to the Elecsys-AMH assay in terms of technical performance for clinical or epidemiological use. Both automated assays performed in a similar way and the choice of assay can be made depending on the technical configuration of each laboratory.

Evaluation of rapid screening techniques for detection of Salmonella spp. from produce samples after pre-enrichment according to FDA BAM and a short secondary enrichment.

UNLABELLED: Conventional detection of Salmonella from foods involves enrichment and isolation on selective media which can significantly lengthen time to result. The objective of this study was to evaluate the utility of an accelerated plating procedure and the use of rapid screening devices for Salmonella detection. Fresh produce was inoculated with Salmonella at ~2·5, ~7·5 and ~25 CFU sample(-1) . After 24 h pre-enrichment, subcultures were made into TT and RV broths and further incubated at 42°C for an additional 7 and 24 h. Enrichments were streaked for isolation of Salmonella as well as tested by rapid screening methods. The 7-h accelerated plating procedure worked well from 4/6 to 6/6 in all produce samples inoculated at the lowest level. Both the RapidChek and Neogen Reveal tests worked as well as the VIDAS-SLM after 24 h secondary enrichment, but failed to detect the pathogen after 7 h selective enrichment in romaine lettuce and tomatoes, while fractional detection was observed in cilantro and jalapenos. Both devices detected Salmonella on cantaloupe at the lowest level of inoculation. An abbreviated selective enrichment procedure worked well to accelerate the isolation of colonies of Salmonella from contaminated samples providing isolates for further characterization 1 day earlier than standard analysis. SIGNIFICANCE AND IMPACT OF THE STUDY: In the event of a foodborne disease outbreak, rapid identification and characterization of the pathogen is essential to prevent the spread of disease and reduce the number of illnesses. This study reports the utility of an abbreviated secondary enrichment for the isolation of Salmonella in artificially contaminated fresh produce at very low levels. In addition, incorporation of rapid, easy-to-use lateral flow devices to screen enrichments can provide a low cost (equipment and highly trained personnel), high return (rapid identification of contaminated food) investment in the timely pathogen screening of fresh produce.

Evaluation and comparison of rapid methods for the detection of Salmonella in naturally contaminated pine nuts using different pre enrichment media.

Foodborne outbreaks, involving pine nuts and peanut butter, illustrate the need to rapidly detect Salmonella in low moisture foods. However, the current Bacteriological Analytical Manual (BAM) culture method for Salmonella, using lactose broth (LB) as a pre enrichment medium, has not reliably supported real-time quantitative PCR (qPCR) assays for certain foods. We evaluated two qPCR assays in LB and four other pre enrichment media: buffered peptone water (BPW), modified BPW (mBPW), Universal Pre enrichment broth (UPB), and BAX(®) MP media to detect Salmonella in naturally-contaminated pine nuts (2011 outbreak). A four-way comparison among culture method, Pathatrix(®) Auto, VIDAS(®) Easy SLM, and qPCR was conducted. Automated DNA extraction techniques were compared with manual extraction methods (boiling or InstaGene™). There were no significant differences (P > 0.05) among the five pre enrichment media for pine nuts using the culture method. While both qPCR assays produced significantly (P ≤ 0.05) higher false negatives in 24 h pre enriched LB than in the other four media, they were as sensitive as the culture method in BPW, mBPW, UPB, and BAX media. The VIDAS Easy and qPCR were equivalent; Pathatrix was the least effective method. The Automatic PrepSEQ™ DNA extraction, using 1000 µL of pre enrichment, was as effective as manual extraction methods.

Evaluation of the diagnostic performance of the xpert Clostridium difficile assay and its comparison with the toxin A/B enzyme-linked fluorescent assay and in-house real-time PCR assay used for the detection of toxigenic C. difficile.

BACKGROUND: Clostridium difficile genes or toxin can be detected using several laboratory techniques. In this study, we compared the performance of the Xpert C. difficile assay with that of a toxin A/B enzyme-linked fluorescent immunoassay (ELFA) and an in-house real-time PCR assay for the tcdB gene. METHODS: From April 2011 through January 2012, 138 soft or liquid stool samples from 138 adult patients at Paik Hospital were tested using the toxin A/B ELFA, in-house real-time PCR assay, and Xpert C. difficile assay to detect toxigenic C. difficile. Specimens were considered true positives if results were positive in both the in-house real-time PCR for tcdB gene and Xpert C. difficile assays. RESULTS: Sensitivity of the toxin A/B ELFA, in-house tcdB gene real-time PCR, and Xpert C. difficile assay were 67.6%, 97.3%, and 100.0%, respectively. The specificity of the in-house tcdB gene real-time PCR assay was 100%, while the specificity was 98.0% for the other two methods. The turnaround time (TAT) was 50 min for the Xpert C. difficile assay, 75 min for the toxin A/B ELFA, and 160 min for the in-house real-time PCR assay. CONCLUSION: The Xpert C. difficile assay and the in-house real-time PCR assay had higher sensitivity than the toxin A/B ELFA; however, the specificities of the three assays were similar. Considering its rapid TAT and high sensitivity, use of the Xpert C. difficile assay is highly recommended for rapid and accurate diagnosis of C. difficile infection.

VIDAS3® TB-IGRA assay: evaluation of performance characteristics in a predominantly low risk, low incidence population.

OBJECTIVES: To evaluate the analytical performance of the TB-IGRA® assay on the VIDAS3 platform (bioMérieux) when testing a predominantly low risk population in a low incidence area. RESULTS: Eighty-eight percent of the results were concordant between QuantiFERON®-TB Gold-Plus (QFT®-Plus, QIAGEN) and TB-IGRA®. All 12 of 99 (12.1%) discordant results were determined positive only with the TB-IGRA® assay. In 11 of 12 of these discordant cases, no explanation could be found in the medical record. Five of these discrepant results were probably caused by the use of contaminated stimulation reagents. The remaining 6 discrepant samples were also part of the reproducibility experiment and only 2 results were reproducible positive. Overall, in the reproducibility experiment 5 of 25 (20.0 %) results were not repeatable. CONCLUSIONS: the TB-IGRA® assay seems prone to contamination. Besides, we documented a reproducibility of only 80.0% with the TB-IGRA® assay.

Comparison between qPCR, VIDAS immunoassays, and agar streaking for the detection of Listeria monocytogenes from food and environmental surfaces containing and not containing Listeria innocua.

Comparisons among a qPCR assay, VIDAS® assays and a conventional agar streaking method following the same enrichment for the detection of Listeria monocytogenes were performed under two challenging conditions. In the first comparison, L. innocua and L. monocytogenes were coinoculated into sausages at ratios (L. innocua-to-L. monocytogenes) of 10, 100, 1000, and 10 000. qPCR provided the most sensitive detection at all ratios after both 24-h and 48-h enrichments. A modified VIDAS® LMO2 assay (i.e., replacement of the kit-specified enrichment scheme with the enrichment scheme used in this study) and agar streaking yielded equivalent results when the ratio was 10 and 100; agar streaking was more sensitive when the ratio was 1000; neither method could detect L. monocytogenes at the ratio of 10 000. Enrichment duration of 48 h was needed for modified VIDAS® to detect L. monocytogenes when the ratio was 1000. Agar streaking after 24-h enrichment isolated L. monocytogenes better than after 48-h enrichment when the ratio was 100 and 1000. In the second comparison, we followed the validation guidelines of AOAC International and inoculated L. monocytogenes, without any L. innocua, onto lettuce and stainless-steel surfaces at low levels. The numbers of positive samples detected by qPCR, VIDAS® LIS assay, modified VIDAS® LMO2 assay, and agar streaking after 48-h enrichment were not statistically different. Our data showed that qPCR was the most sensitive method, while agar streaking and VIDAS® performed reasonably well. Streaking after 24-h enrichment was needed when background flora could overgrow L. monocytogenes during prolonged enrichment, and this is critical for confirming rapid screening assays. Appropriate selection of enrichment duration and rapid assays will enhance the testing of L. monocytogenes in food and environmental samples.

Performance of VIDAS® Diagnostic Tests for the Automated Detection of Dengue Virus NS1 Antigen and of Anti-Dengue Virus IgM and IgG Antibodies: A Multicentre, International Study.

Dengue is a serious mosquito-transmitted disease caused by the dengue virus (DENV). Rapid and reliable diagnosis of DENV infection is urgently needed in dengue-endemic regions. We describe here the performance evaluation of the CE-marked VIDAS® dengue immunoassays developed for the automated detection of DENV NS1 antigen and anti-DENV IgM and IgG antibodies. A multicenter concordance study was conducted in 1296 patients from dengue-endemic regions in Asia, Latin America, and Africa. VIDAS® dengue results were compared to those of competitor enzyme-linked immunosorbent assays (ELISA). The VIDAS® dengue assays showed high precision (CV ≤ 10.7%) and limited cross-reactivity (≤15.4%) with other infections. VIDAS® DENGUE NS1 Ag showed high positive and negative percent agreement (92.8% PPA and 91.7% NPA) in acute patients within 0-5 days of symptom onset. VIDAS® Anti-DENGUE IgM and IgG showed a moderate-to-high concordance with ELISA (74.8% to 90.6%) in post-acute and recovery patients. PPA was further improved in combined VIDAS® NS1/IgM (96.4% in 0-5 days acute patients) and IgM/IgG (91.9% in post-acute patients) tests. Altogether, the VIDAS® dengue NS1, IgM, and IgG assays performed well, either alone or in combination, and should be suitable for the accurate diagnosis of DENV infection in dengue-endemic regions.

Performance Evaluation of VIDAS® Diagnostic Assays Detecting Anti-Chikungunya Virus IgM and IgG Antibodies: An International Study.

Chikungunya (CHIK) is a debilitating mosquito-borne disease with an epidemiology and early clinical symptoms similar to those of other arboviruses-triggered diseases such as dengue or Zika. Accurate and rapid diagnosis of CHIK virus (CHIKV) infection is therefore challenging. This international study evaluated the performance of the automated VIDAS® anti-CHIKV IgM and IgG assays compared to that of manual competitor IgM and IgG ELISA for the detection of anti-CHIKV IgM and IgG antibodies in 660 patients with suspected CHIKV infection. Positive and negative agreements of the VIDAS® CHIKV assays with ELISA ranged from 97.5% to 100.0%. The sensitivity of the VIDAS® CHIKV assays evaluated in patients with a proven CHIKV infection confirmed reported kinetics of anti-CHIKV IgM and IgG response, with a positive detection of 88.2-100.0% for IgM ≥ 5 days post symptom onset and of 100.0% for IgG ≥ 11 days post symptom onset. Our study also demonstrated the superiority of ELISA and VIDAS® assays over rapid diagnostic IgM/IgG tests. The analytical performance of VIDAS® anti-CHIKV IgM and IgG assays was excellent, with a high precision (coefficients of variation ≤ 7.4%) and high specificity (cross-reactivity rate ≤ 2.9%). This study demonstrates the suitability of the automated VIDAS® anti-CHIKV IgM and IgG assays to diagnose CHIKV infections and supports its applicability for epidemiological surveillance and differential diagnosis in regions endemic for CHIKV.

Use of a simplified non-invasive technic to monitor fecal progesterone metabolites and reproduction function in several zoo species: Efficacy of mini VIDAS® automate (bioMérieux).

Developing the zoos' ability to assess the reproductive status of the individuals they house is essential to improve the husbandry and management of these species. The use of non-invasive techniques such as fecal hormone analysis has been proven to be a simple and effective way to achieve this. Designed by bioMérieux, mini VIDAS® instrument is used in human and veterinary medicine to evaluate different endocrinological parameters, including serum or plasma progesterone. This study evaluates VIDAS® Progesterone (PRG) assay's efficacy to monitor fecal progestagens using a simple sample extraction protocol adapted to the zoo environment. We compared (1) VIDAS® PRG fecal profiles with established assays specifically designed for fecal progestagens analysis at the VetmedUni (Vienna, Austria) for okapis (Okapia johnstoni), greater one-horned rhinoceros (Rhinoceros unicornis), giraffes (Giraffa camelopardalis reticulata) and hippopotamus (Hippopotamus amphibius) (2) VIDAS® PRG fecal profiles with VIDAS® PRG serum profiles for African elephants (Loxodonta Africana), giant anteater (Myrmecophaga tridactyla) and white rhinoceros (Ceratotherium simum). Spearman mean correlations were: 0.6748 for African elephants (n = 2 animals), 0.7969 for giant anteater (n = 1 animal), 0.7926 for okapis (n = 2 animals), 0.6072 for greater one-horned rhinoceros (n = 4 animals), 0.6062 for giraffes (n = 4 animals) and 0.5740 for hippopotamus (n = 2 animals). Fecal progestagens analysis revealed estrous cycles in several species: 12.5 ± 0.5 weeks for African elephants (n = 2 cycles), 15.3 ± 1.1 days for okapis (n = 6 cycles), 44 ± 2.1 days for greater one-horned rhinoceros (n = 4 cycles) and 15.5 ± 0.5 days for giraffes (n = 4 cycles). We observed pregnancies in a giant anteater, an okapi and a hippopotamus. We observed a strong positive Spearman correlation (r > 0.60) for individuals exhibiting estrous cycles. These first results indicate that the mini VIDAS® can be used for monitoring of the reproductive status of non-domesticated species and can be a useful tool for the reproductive management through fecal progesterone analysis. A simple extraction protocol was suitable for sample preparation of fecal progesterone metabolite analysis. Further studies using a larger number of individuals per species at different reproductive stages could confirm the relevance of mini VIDAS® in the zoo community.

Comparative Evaluation of Three Immunoassays for the Simultaneous Detection of Clostridioides difficile Glutamate Dehydrogenase and Toxin A/B.

BACKGROUND: In the medical laboratory, a step-by-step workflow for Clostridioides difficile infection (CDI) detection using glutamate dehydrogenase (GDH) and toxin A/B assays for initial screening, along with a nucleic acid amplification test (NAAT), has been recommended recently. In this study, we evaluated these three immunoassays for the simultaneous detection of GDH and Clostridioides difficile (CD) toxin A/B. METHODS: A total of 304 stool samples were tested for the presence of GDH antigen and CD toxin A/B using VIDAS C. difficile GDH and toxin A/B (CDAB), RIDASCREEN C. difficile GDH and toxin A/B (RIDA), and C. DIFF QUIK CHEK COMPLETE according to the manufacturers' recommendations. As complementary reference methods for GDH and toxin A/B detection in the three immunoassays, CD cultures using ChromID C. difficile agar and the Xpert C. difficile assay, respectively, were tested. RESULTS: All three GDH assays showed overall substantial agreement with the CD culture. All three toxin A/B assays showed overall moderate agreement with the Xpert C. difficile assay. In comparison with consensus results, VIDAS GDH and QCC GDH showed almost perfect agreement, whereas RIDA GDH showed inferior but substantial agreement. All three toxin A/B assays showed almost perfect agreement. CONCLUSIONS: Since the QCC GDH and toxin A/B assay is relatively more sensitive and specific than the other two immunoassays for discriminating toxigenic or non-toxigenic CDI, QCC is very helpful for the simultaneous identification of GDH and CD toxin A/B in the initial step of the two-round workflow for diagnosing CDI.

Evaluation of a Prototype of a Novel Galactomannan Sandwich Assay Using the VIDAS® Technology for the Diagnosis of Invasive Aspergillosis.

Objectives: To evaluate the analytical and clinical performance of a prototype of a VIDAS® Galactomannan (GM) unitary test (bioMérieux, Marcy l'Etoile, France) and compare to that of the Platelia™ Aspergillus Ag assay (Bio-Rad, CA, USA). Methods: Repeatability, reproducibility, and freeze-thaw stability of VIDAS®GM were evaluated. Sera from patients at risk of IA were concurrently tested with both the VIDAS®GM and Platelia™ Aspergillus Ag assays. Correlations between the two assays were assessed by Passing Bablok (PB) regression and performance by ROC analysis. Results: The correlations between the VIDAS®GM indexes after one and two cycles of freezing/thawing were r=1.00 and r=0.989, respectively. The coefficients of variation for negative, low-positive, and positive sera were 13%, 6%, and 5% for repeatability and 14.4%, 7.2%, and 5.5% for reproducibility. Overall, 126 sera were tested with both assays (44 fresh and 82 frozen). The correlation between VIDAS®GM and Platelia™ Aspergillus Ag was r=0.798. The areas under the curve of the ROC analyses were 0.892 and 0.894, for VIDAS®GM and Platelia™ Aspergillus Ag, respectively. Conclusions: This new VIDAS®GM prototype assay showed adequate analytical and clinical performance and a good correlation with that of Platelia™ Aspergillus Ag with 126 sera, although these results need to be confirmed in a larger prospective and multicentric study. As for the other VIDAS® assays, VIDAS®GM is a single-sample automated test using a solid reagent strip and receptacle. It is easy to use and suitable for rapid on-demand test results.

Influence of Food Matrices and the Population of Interfering Microorganisms on the Determination of Listeria monocytogenes by Conventional Methods and VIDAS.

In this study, the possible influence of the food matrix and the interfering population of microorganisms on the detection and count of Listeria monocytogenes in three common foods of the Spanish diet (Spanish omelette, fresh cheese and vegetable salad) was determined. Four groups were assayed: one control, two groups with interfering microorganisms (Salmonella Enteritidis, Staphylococcus aureus and Proteus mirabilis) with different levels of L. monocytogenes and a final group only contaminated with L. monocytogenes. The samples were analyzed with the normalized method (UNE-EN ISO 11290:2018) and with an alternative technique (VIDAS). The results show that the presence of interfering microorganisms did not seem to interfere with the determination of L. monocytogenes. Furthermore, the type of food did not seem to influence the determination of L. monocytogenes, but the culture media used showed differences. In fact, regardless of the type of food, the ALOA medium showed higher sensitivity than the other media, with higher recovery in 100% of samples (only for the Spanish omelette in Group B was the result the same as that for PALCAM, -8.11 log cfu/g). The results obtained using the VIDAS were not influenced by any of the factors or conditions used and show 100% efficiency.

Evaluation of VIDAS® Diagnostic Assay Prototypes Detecting Dengue Virus NS1 Antigen and Anti-Dengue Virus IgM and IgG Antibodies.

Dengue is a serious tropical disease caused by the mosquito-borne dengue virus (DENV). Performant, rapid, and easy-to-use assays are needed for the accurate diagnosis of acute DENV infection. We evaluated the performance of three prototype assays developed for the VIDAS® automated platform to detect dengue NS1 antigen and anti-dengue IgM and IgG antibodies. Positive and negative agreement with competitor enzyme-linked immunosorbent assays (ELISA) and rapid diagnostic tests (RDT) was evaluated in 91 Lao patients (57 adults, 34 children) with acute DENV infection. The VIDAS® NS1 assay showed the best overall agreement (95.6%) with the competitor NS1 ELISA. Both VIDAS® NS1 and NS1 ELISA assays also demonstrated high sensitivity relative to DENV RNA RT-PCR set as gold standard (85.7% and 83.9%, respectively). In contrast, NS1 RDT was less sensitive relative to DENV RNA RT-PCR (72.7%). The overall agreement of VIDAS® IgM and IgG assays with the competitor assays was moderate (72.5% for IgM ELISA, 76.9% for IgG ELISA, and 68.7% for IgM and IgG RDT). In most analyses, test agreements of the VIDAS® assays were comparable in adults and children. Altogether, the VIDAS® dengue prototypes performed very well and appear to be suitable for routine detection of dengue NS1 antigen and anti-dengue IgM/IgG antibodies.

Comparative study of SARS-CoV-2 antibody titers between male and female COVID-19 patients living in Kurdistan region of Iraq.

Recently, there is increasing evidence that coronavirus disease 2019 (COVID-19) causes men to experience more serious symptoms and have a higher mortality rate than women, but the association between sex and immune response stays unknown till now, and weather patient's prognosis associated with sex or not is another vague in COVID-19. In this study, the SARS-CoV-2-specific antibody titer test was performed for 727 patients who were a positive RT-PCR result for COVID-19 and we determined the difference in immune response in both genders. Patients were divided into two groups based on their genders, which were 383 males and 344 females. Plasma was collected from the patients after 17 days of diagnosis with COVID-19, and the concentrations of specific antibodies (IgG and IgM) was measured by multiparametric immunoassay system (VIDAS). Results demonstrated that there was no significant difference in both IgM and IgG production in male participants compared to women. Moreover, despite there was a weak significant positive association between age and IgM in male patients, while there was no significant correlation between IgG and age for the same gender. On the other hand, a slight positive correlation between IgM and IgG with age was observed in female participants. Finally, it concluded that there was no sex biases in patients with COVID-19 in Erbil, Iraq. So, these findings are crucial to treat and care male and female's patients infected with COVID-19 at hospitals.

Evaluation of the diagnostic performance and optimal cutoff value of a fourth-generation ELISA, VIDAS HIV-1/2 Duo Ultra assay, in a low-prevalence country.

In this study, we described the largest analysis to date conducted with VIDAS® HIV Duo Ultra assay. Additionally, we analyzed the diagnostic performance and cutoff values (TV) of HIV Duo Ultra assay and total cost analysis for HIV testing. Of 11,642 enzyme-linked immunosorbent assay (ELISA)-positive samples referred to our center for confirmation, 2000 were positive with HIV Duo Ultra, and of these, 87% were HIV-1 positive and 0.6% were HIV-1 indeterminate with the confirmatory test. Overall, the false-positivity rate was 1.75% for HIV Duo Ultra assay. The sensitivity and specificity were 100% and 99.1%, respectively, when the TV was set at the recommended cutoff value. Even increasing the cutoff value four times, sensitivity and specificity remained high, pointing out that a TV of 0.99 is highly indicative of HIV positivity. Retesting samples with HIV Duo Ultra assay decreased 80% of the confirmatory tests, revealing a significant decrease of 78% in the total costs and reporting time.