Diagnostic value of IgG antibody and stool antigen tests for chronic Helicobacter pylori infections in Ibb Governorate, Yemen.

The stool antigen test (SAT) and the serum Helicobacter pylori (H. pylori) IgG antibody assays exhibit significant utility in the clinical diagnosis of H. pylori infection and in distinguishing between acute and chronic infections. The main objective of the current study was to identify the diagnostic value of serum H. pylori IgG antibody and SAT in the detection of H. pylori infections among chronic H. pylori-infected patients residing in Ibb Governorate, Yemen. 200 patients with H. pylori infection, confirmed through positive results in the serum immunochromatographic antibody test, were selected for H. pylori infection confirmation using serum H. pylori IgG antibodies and SAT across diverse hospitals, gastroenterology, and Hepatology clinics in Ibb Governorate. After the selection of patients, blood and stool specimens were obtained from all participants and underwent analysis via the Statistical Package for the Social Sciences (SPSS). The prevalence of H. pylori infection demonstrated variability based on the confirmatory tests, with rates of 54% for SAT and 78.5% for serum H. pylori IgG antibody, contrasting with a 100% prevalence observed in the screening serum immunochromatographic antibody test. Clinically, the study categorized H. pylori infections into four stages, whereby a significant proportion of patients (40.5%) exhibited positivity for both serum H. pylori IgG antibody and SAT, indicative of active chronic infections. The majority of positive cases only manifested serum H. pylori IgG antibody presence (chronic infections) at 38%, whereas 13.5% exclusively tested positive for SAT, corresponding to acute infections. Moreover, 88% of patients did not have either serum H. pylori IgG antibody or SAT (absence of infections) during confirmatory tests. Noteworthy is the study's approach employing multiple tests for H. pylori infection detection, focusing predominantly on chronic infections-prevailing types caused by H. pylori. The results revealed a significant association between serum levels of H. pylori IgG antibody and SAT results with the presence of diverse gastrointestinal symptoms among patients, which increased with long H. pylori infection durations.

Seroprevalence of Infection by Borrelia Species Responsible for Lyme Disease in the French Alps: Analysis of 27,360 Serology Tests, 2015-2020.

Objectives: Lyme borreliosis incidence is increasing in several areas; moreover, it has recently gained the public's attention. Apart from erythema migrans, Lyme disease diagnosis relies (among others) on serology test; however, the prevalence of positive enzyme-linked immunosorbent assay (ELISA) and western blot (WB) assay has been poorly studied in the general population. We aimed to approach the seroprevalence of infection by Borrelia species responsible for Lyme disease in the French Isere department using city laboratories data. Patients and Methods: We retrieved all serological tests for Borrelia species responsible for Lyme disease performed in the two main networks of city laboratories between 2015 and 2020. All patients with both ELISA and WB IgG were considered seropositive. Results: We analyzed 27,360 tests (ELISA/ELISA+WB). Mean age was 50.9 ± 20.3 years (ranges: 0-101), with 57.1% females. Overall, 11.7% had IgG detected by ELISA, and 4.7% had IgG detected by both ELISA and WB assay. Seropositive status was more frequent in males (7.0% vs. 2.9%, p < 0.001). Seropositivity rate increased with age after a first peak in childhood; men aged 61-70 years had the highest seropositivity rate (10.3%). In addition, seropositivity rate was higher in persons from a rural area. In multivariate analysis, older age, male gender and living in a rural area were independently associated with seropositivity. Seropositivity rate was stable on the 2017-2020 period. Conclusion: The seroprevalence of infection by Borrelia species responsible for Lyme disease is high in Isere; this probably reduces the predictive positive value for Lyme disease of ELISA and WB IgG, suggesting that this serological test should not be performed for nonspecific symptoms.

Analysis of diagnostic test outcomes in a large loiasis cohort from an endemic region: Serological tests are often false negative in hyper-microfilaremic infections.

BACKGROUND: The parasitic disease loiasis is associated with significant morbidity and mortality. Individuals with hyper-microfilaremia (greater than 20,000 microfilariae per mL of blood) may suffer from serious treatment-related or spontaneous adverse events. Diagnosing loiasis remains complex and primarily relies on direct parasite detection. In this study, we analyzed the performance of various diagnostic tests and the influence of parasitological and clinical factors on test outcomes in samples from individuals living in an endemic region. METHODS: Data and samples were collected from rural Gabon. Loiasis was defined as either detectable microfilaremia, or a positive history of eyeworm as assessed by the RAPLOA questionnaire. Diagnostic testing included a quantitative PCR (qPCR) for detection of Loa loa DNA in blood samples, an in-house crude L. loa antigen IgG ELISA, and a rapid test for antibodies against the Ll-SXP-1 antigen (RDT). Sensitivity and specificity were determined for each test and factors potentially influencing outcomes were evaluated in an exploratory analysis. RESULTS: ELISA, RDT and qPCR results were available for 99.8%, 78.5%, and 100% of the 1,232 participants, respectively. The ELISA and RDT had only modest diagnostic accuracy. qPCR was specific for L. loa microfilaremia and Cycle threshold values correlated with microfilarial density. Anti-L. loa IgG levels were highest in occult loiasis, and antibody levels correlated inversely with L. loa microfilarial density as did RDT line intensities. Only 84.6% and 16.7% of hyper-microfilaremic individuals tested positive by ELISA (11/13) and RDT (2/12), respectively. CONCLUSION: None of the tests demonstrated high sensitivity and specificity for loiasis. Indirect diagnostic assays were characterized by low specificity. Additionally, hyper-microfilaremic individuals often tested negative by RDT and ELISA, indicating that these tests are not suitable for individual case management in endemic populations.

Diagnostic accuracy of serological rk-39 test for visceral Leishmaniasis: Systematic review and meta-analysis.

BACKGROUND: Visceral leishmaniasis (VL), or kala-azar, is a vector-borne tropical disease caused by a group of intracellular hemoflagellate protozoa belonging to the family of Trypanosomatide and the genus Leishmania. The disease is distributed around the world and transmitted via the bite of infected female Phlebotomine sandflies, and there is variation in the diagnostic accuracy. Therefore, this systematic review and meta-analysis aimed to determine the pooled global sensitivity and specificity of the rk-39 test and to evaluate if there is a difference between the different parts of the world. METHODS: A systematic review and meta-analysis have been conducted on the diagnostic accuracy of dermoscopy. After setting eligibility criteria, literature was searched in four databases and one searching engine. Articles were screened, critically appraised, and extracted independently by two reviewers, and any disagreements were resolved with the involvement of a third person. The quality of the included studies had been assessed by the Quality Assessment of Diagnostic Accuracy Studies (QUADAS 2) tool. Pooled sensitivity and specificity were determined by bivariate random effect analysis. Heterogeneity was assessed by Higgins's I2, and when it was present, mitigation was conducted by using sensitivity analysis. RESULT: A total of 409 studies were identified, and finally 18 articles were eligible for the review with a total sample size of 5, 253. The bivariate random effect meta-analysis of the 7 diagnostic accuracy studies showed a pooled sensitivity of 0.89 (0.76-0.95) and specificity of 0.86 (0.72-0.94). The +LR was 6.32 (95% CI: 2.85-14.02), the-LR was 0.13 (95% CI: 0.06-0.30), and the diagnostic odds ratio (DOR) was 47.8 (95% CI: 11.3-203.2). Abdel-Latif (2018) was both an outlier and influential for sensitivity, and Walter (2011) was both an outlier and influential for specificity, and removing them from sensitivity and specificity, respectively, was beneficial for reducing the heterogeneity. CONCLUSION: Rk-39 is found to have highly accurate measures in the diagnosis of visceral leishmaniasis. Both sensitivity and specificity were found to be highly accurate in the diagnosis of leishmaniasis, with a pooled sensitivity of 0.91 (0.88-0.93) and a pooled specificity of 0.89 (0.85-0.91). ETHICAL CONSIDERATION: As we will use secondary data for the systematic review and meta-analysis, ethical concerns are not necessary.

A multi-country comparative study of two treponemal tests for the serodiagnosis of syphilis amongst men who have sex with men (MSM): Chemo-luminescent assay vs Treponema pallidum particle agglutination assay.

INTRODUCTION: International guidelines recommend routine screening for syphilis (aetiological agent: Treponema pallidum subspecies pallidum) amongst key populations and vulnerable populations using tests detecting treponemal and non-treponemal antibodies. Whilst treponemal tests have high sensitivities and specificities, they differ regarding subjective or objective interpretation, throughput and workload. Chemiluminescence immunoassays (CLIAs) are cost- and time-effective automated methods for detecting treponemal antibodies. The Treponema pallidum particle agglutination assay (TPPA) has been considered the "gold standard" treponemal assay, however, this includes a highly manual procedure, low throughput and subjective interpretation. The present multi-country study evaluated the ADVIA Centaur® Syphilis CLIA (Siemens Healthcare) assay compared to the reference SERODIA-TP·PA® (Fujirebio Diagnostics) for the serodiagnosis of syphilis amongst men who have sex with men (MSM). METHOD: 1,485 MSM were enrolled in Brighton (UK), Malta, and Verona (Italy) as part of a larger WHO multi-country and multi-site ProSPeRo study. Ethical approval was obtained. Serum was tested with the ADVIA Centaur® Syphilis CLIA assay and SERODIA-TP·PA®, in accordance with the manufacturers' instructions, for a first round of validation. A second round of validation was carried out for discrepant results that were additionally tested with both Western Blot (Westernblot EUROIMMUN®) and an Immunoblot (INNO-LIA, Fujirebio Diagnostics). Sensitivity, specificity, positive and negative predictive value (PPV and NPV), likelihood ratios (positive/negative), and the Diagnostic Odds Ratio (DOR)/pre-post-test probability (Fagan's nomogram) were calculated. RESULTS: Out of 1,485 eligible samples analysed in the first phase, the SERODIA-TP·PA® identified 360 positive and 1,125 negative cases. The ADVIA Centaur® Syphilis CLIA assay (Siemens) identified 366 positives, missclassifying one TPPA-positive sample. In the second phase, the ADVIA Centaur® Syphilis CLIA resulted in 1 false negative and 4 false positive results. Considering the syphilis study prevalence of 24% (95% CI: 22-26.7), The sensitivity of the ADVIA Centaur® Syphilis CLIA assay was 99.7% (95% CI: 98.5-100), and the specificity was 99.4% (95% CI: 98.7-99.7). The ROC area values were 0.996 (95% CI: 0.992-0.999), and both the PPV and NPV values were above 98% (PPV 98.1%, 95% CI: 96.1-99.2; NPV 99.9%, 95% CI: 99.5-100). CONCLUSIONS: The ADVIA Centaur® Syphilis CLIA assay showed similar performance compared to the SERODIA-TP·PA®. Considering the study is based on QUADAS principles and with a homogeneous population, results are also likely to be generalisable to MSM population but potentially not applicable to lower prevalence populations routinely screened for syphilis. The automated CLIA treponemal assay confirmed to be accurate and appropriate for routine initial syphilis screening, i.e. when the reverse testing algorithm is applied.

Approaching the complexity of Crimean-Congo hemorrhagic fever virus serology: A study in swine.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne zoonotic orthonairovirus of public health concern and widespread geographic distribution. Several animal species are known to seroconvert after infection with CCHFV without showing clinical symptoms. The commercial availability of a multi-species ELISA has led to an increase in recent serosurveillance studies as well as in the range of species reported to be exposed to CCHFV in the field, including wild boar (Sus scrofa). However, development and validation of confirmatory serological tests for swine based on different CCHFV antigens or test principles are hampered by the lack of defined control sera from infected and non-infected animals. For the detection of anti-CCHFV antibodies in swine, we established a swine-specific in-house ELISA using a panel of swine sera from CCHFV-free regions and regions with reported CCHFV circulation. We initially screened more than 700 serum samples from wild boar and domestic pigs and observed a correlation of ≃67% between the commercial and the in-house test. From these sera, we selected a panel of 60 samples that were further analyzed in a newly established indirect immunofluorescence assay (iIFA) and virus neutralization test. ELISA-non-reactive samples tested negative. Interestingly, only a subset of samples reactive in both ELISA and iIFA displayed CCHFV-neutralizing antibodies. The observed partial discrepancy between the tests may be explained by different test sensitivities, antibody cross-reactivities or suggests that the immune response to CCHFV in swine is not necessarily associated with eliciting neutralizing antibodies. Overall, this study highlights that meaningful CCHFV serology in swine, and possibly other species, should involve the performance of multiple tests and careful interpretation of the results.

Development of an indirect ELISA for the serodiagnosis of canine infection by Onchocerca lupi.

Onchocerca lupi is a zoonotic filarioid parasite of dogs and cats with widespread distribution. A specific non-invasive diagnostic assay for the detection of O. lupi infections remains unavailable. This study aimed to assess the accuracy, specificity, and sensitivity of an ELISA test designed using nine peptides from two O. lupi proteins. Sera (n = 54) collected from O. lupi infected dogs from endemic areas (Portugal and USA), alongside sera from dogs positive for Dirofilaria immitis, D. repens, Cercopithifilaria bainae, and Acanthocheilonema reconditum (n = 53) from a non-endemic area for O. lupi, as well as from helminth-free dogs (n = 60), were tested. The checkerboard titration method was applied for the optimization of peptide concentrations and conjugate anti-dog dilutions. Sensitivity, specificity, and optimal cut-off values were calculated using ROC curve analysis. All peptides reacted against sera of O. lupi, with no correlation between optic density (OD) values and microfilariae (mfs) loads. Sensitivity and specificity values ranging from 85.45 to 100%, and 88.89% to 100%, respectively, were recorded for all peptides examined, with 100% specificity and sensitivity observed for peptides 40_3, 40_5, 130_3, 120_3 and 40_1, 130_5, respectively. The maximum cut-off value was observed for peptides 40_5 (0.765) and 40_3 (0.708). Testing of sera from dogs positive for other filarioids resulted in lower OD values (up to 1.565) for peptides 40_3 and 40_5 when compared with O. lupi (up to 2.929). The availability of this assay will be of value in epidemiological studies of canine O. lupi infection in both endemic and non-endemic areas, and in assessing the risk for zoonotic transmission.

CDC Laboratory Recommendations for Syphilis Testing, United States, 2024.

This report provides new CDC recommendations for tests that can support a diagnosis of syphilis, including serologic testing and methods for the identification of the causative agent Treponema pallidum. These comprehensive recommendations are the first published by CDC on laboratory testing for syphilis, which has traditionally been based on serologic algorithms to detect a humoral immune response to T. pallidum. These tests can be divided into nontreponemal and treponemal tests depending on whether they detect antibodies that are broadly reactive to lipoidal antigens shared by both host and T. pallidum or antibodies specific to T. pallidum, respectively. Both types of tests must be used in conjunction to help distinguish between an untreated infection or a past infection that has been successfully treated. Newer serologic tests allow for laboratory automation but must be used in an algorithm, which also can involve older manual serologic tests. Direct detection of T. pallidum continues to evolve from microscopic examination of material from lesions for visualization of T. pallidum to molecular detection of the organism. Limited point-of-care tests for syphilis are available in the United States; increased availability of point-of-care tests that are sensitive and specific could facilitate expansion of screening programs and reduce the time from test result to treatment. These recommendations are intended for use by clinical laboratory directors, laboratory staff, clinicians, and disease control personnel who must choose among the multiple available testing methods, establish standard operating procedures for collecting and processing specimens, interpret test results for laboratory reporting, and counsel and treat patients. Future revisions to these recommendations will be based on new research or technologic advancements for syphilis clinical laboratory science.

Simple and promising paper-based electrochemical platform for serological detection of American tegumentary leishmaniasis.

BACKGROUND: American tegumentary leishmaniasis (ATL) is an endemic neglected tropical disease (NTD), its conventional treatment is toxic, slow, and invasive. Rapid diagnosis is crucial for the clinical management of suspected patients, so the development and use of low-cost, miniaturised and portable devices could be the key. OBJECTIVES: This work aimed to develop a simple paper-based electrochemical platform for the serological detection of ATL. METHODS: Platform was fabricated in Whatman N°1 paper, contains a hydrophobic zone generated by wax printing, two pencil graphite electrodes, and uses specific crude extracts (CA) antigens for ATL immuno-determination. The platform performance was analysed by measuring the relative impedance change for different antigen-antibody combinations. Then, 10 serum human samples previously diagnosed by the gold standard (five positive ATL cases and five non-ATL cases) were evaluated. FINDINGS: The platform presented a linear response for the charge transfer resistance (ΔRct) and the interface reactance (ΔXc). Also, optimal working conditions were established (1/60 serum dilution and 180 µg/mL CA concentration). Then, the platform permits to distinguish between ATL and non-ATL (p < 0.05) human serum samples. MAIN CONCLUSIONS: Our platform could allow the diagnosis, management, and monitoring of leishmaniasis while being an extremely simple and environmentally friendly technology.

Bayesian evaluation of temporal changes in sensitivity and specificity of three serological tests for multiple circulating strains of rabbit haemorrhagic disease virus.

Competition and indirect ELISAs are currently being used to monitor rabbit haemorrhagic disease viruses (RHDV1 and RHDV2) in rabbits worldwide. Temporal changes in the sensitivity (Se) and specificity (Sp) of RHDV1 competition-ELISA (cELISA1), RHDV2 competition-ELISA (cELISA2), and RHDV1 Immunoglobulin G (IgG1) ELISA, were investigated using Bayesian Latent Class models (BCLM) in the Australian wild rabbit population where both viruses circulate simultaneously and a long-term serological dataset exists. When cELISA1 was compared to IgG1 ELISA, the Se of cELISA1 improved while the Sp of IgG1 ELISA declined over the 2011-21. This corresponded with a decline in the true RHDV1 prevalence in 2018-21, suggesting that a large proportion of RHDV1 exposed rabbits survived the introduction and dominance of RHDV2 up to approximately 2017/2018, after which they died and were not replaced. The Se and Sp estimates for 2014-15 for both cELISA1 and IgG1 ELISA, and the true prevalence when analysing all three tests together were similar to those obtained from the analysis of cELISA1/IgG1 ELISA. The same was also true for the Se and Sp of cELISA2 and IgG1 ELISA estimates from 2018 onwards. This suggests that RHDV1 was the dominant infection type in 2014-15, but RHDV2 was the dominant infection type in 2018-21. Further, the increase in Se of cELISA2 and the low Sp of IgG1 ELISA in the cELISA2/IgG1 ELISA analysis, compared to the Se of cELISA2 and Sp of IgG1 ELISA when analysing all three tests together suggests that the underlying infection status was more influenced by RHDV2 and that the higher Se of IgG1 ELISA is due to cross-reaction of RHDV2 antibodies on IgG1 ELISA. The true prevalence data suggest that RHDV2 exposure peaked in 2017. Our findings show that test characteristics changed in response to the changing virus prevalences over time. IgG1 ELISA, currently having a high Se, should be used to monitor both viruses and will perform better than both cELISAs.

Usefulness of a new immunochromatographic assay using fluorescent silica nanoparticles for serodiagnosis of Thai patients with amebiasis.

A fluorescence immunochromatography (FIC) kit was developed recently using fluorescent silica nanoparticles coated with a recombinant C-terminal fragment of the surface lectin intermediate subunit (C-Igl) of Entamoeba histolytica to establish rapid serodiagnosis of amebiasis. We further evaluated the system using serum samples from 52 Thai patients with amebiasis. Of the patients, 50 (96%) tested positive using FIC. The samples were also tested using enzyme-linked immunosorbent assay (ELISA) with C-Igl as the antigen. Two samples were negative on ELISA but positive on FIC. The correlation coefficient between the fluorescence intensity using FIC and the optical density value using ELISA was 0.5390, indicating a moderate correlation between the two tests. Serum samples from 20 patients with malaria and 22 patients with Clostridioides difficile infection were also tested using FIC. The false-positive rates were 4/20 (20%) and 1/22 (4%) in patients with malaria and C. difficile infection, respectively. Combining the data from the present study with our previous study, the sensitivity and specificity of FIC were determined to be 98.5% and 95.2%, respectively. The results of the 50 samples were studied using a fluorescence scope and a fluorescence intensity reader, and the findings were compared. Disagreements were found in only two samples showing near-borderline fluorescence intensity, indicating that the use of scope was adequate for judging the results. These results demonstrate that FIC is a simple and rapid test for the serodiagnosis of amebiasis.

High-speed centrifugation rather than Lipoclear reagent can be used for removing the interference of lipemia on serological tests of infectious diseases: AIDS, hepatitis B, hepatitis C, and syphilis by chemiluminescent microparticle immunoassay.

The aim of this study was to investigate the interference of lipemia on measurement of HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, anti-HCV, HIV Ag/Ab, and anti-TP in serum by chemiluminescent microparticle immunoassay (CMIA) and compare lipemia removing performance between high-speed centrifugation and Lipoclear reagent. Mixed native serum samples (NSs) and hyperlipemia serum samples (HLS) were prepared for the investigated parameters. The levels of these parameters in NS and HLS were determined by CMIA on an Abbott ARCHITECT i2000SR immunoassay analyzer. HBsAg, anti-HBs, and anti-TP were affected with relative bias >12.5% (acceptable limit) when the level of triacylglycerol (TG) was higher than 27.12 mmol/L in HLS. Clinically unacceptable bias were observed for HBeAg and anti-HBe in HLS with TG higher than 40.52 mmol/L. However, anti-HCV and HIV Ag/Ab were not interfered in severe lipemia with TG < 52.03 mmol/L. In addition, the Lipoclear reagent did not reduce the interference of lipemia with relative bias from -62.50% to -18.02%. The high-speed centrifugation under the optimized condition of 12 000g for 10 min successfully removed the interference of lipemia with relative bias from -5.93% to 0% for HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, and anti-TP. To conclude, high-speed centrifugation can be used for removing the interference of lipemia to measure HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, and anti-TP. Accordingly, a standardized sample preanalytical preparation of the patients and other screening participants as well as a specimen examination procedure for removing lipemia interference on the serological tests was recommended.

Design and development of multiepitope chimeric antigens by bioinformatic and bacterial based recombinant expression methods, with potential application for bovine tuberculosis serodiagnosis.

Bovine tuberculosis (bTB), which is caused by Mycobacterium bovis, is a single health concern, which causes economic losses, is a sanitary barrier and is a zoonotic concern. The golden-pattern intradermic tests have low sensitivity of about 50%. To fix this sensitivity problem, immunoassays could be a powerful tool. However, few studies produced antigens for bTB immunoassays, which needs improvements. Aim of this study was to produce multiepitope chimeric antigens (MCA) to use for bTB diagnosis. To achieve MCA design and development, extensive bibliographic search, antigenic epitope prediction, specificity, hydrophobicity, and 3D structure modeling analyses were performed, as well as cloning, expression and purification. Seven epitopes from four different target proteins (MPB-70, MPB-83, ESAT-6 and GroEL) were combined in five chimeras containing five repetitions of each epitope to enhance antibodies affinity. 3D predicted models revealed that all chimeras have a high percentage of disorder, which could enhance antibody recognition, although taking to protein instability. Each chimera was cloned into pET28a (+) expression plasmids and expressed in six Escherichia coli expression strains. Chimeras 3, 4 and 5 could be solubilized in 8 M urea and purified by ion exchange affinity chromatography. Against bTB positive and negative sera, purified chimera 5 had the best results in indirect dot blot and ELISA, as well as in lateral flow dot blot immunoassay. In conclusion, chimera 5, an MPB-83 containing MCA, could be used for further studies, aimed to develop a serologic or rapid test for bTB diagnosis.

Estimates of sensitivity and specificity of serological tests for SARS-CoV-2 specific antibodies using a Bayesian latent class model approach.

OBJECTIVES: Assessing the accuracy of serological tests for SARS-CoV-2 was challenging due to the lack of a gold standard. This study aimed to estimate the accuracy of SARS-CoV-2-specific serological tests using Bayesian latent class models (BLCM) and compare methods with and without a gold standard. STUDY DESIGN AND SETTING: In this study, we analyzed 356 samples-254 positives, ie, from individuals with a previous SARS-CoV-2 infection diagnosis, and 102 negatives, ie, prepandemic samples-using six different rapid serological tests and one laboratory assay. A BLCM was employed to concurrently estimate the sensitivity and specificity of all serological tests for the immunoglobulin (Ig) M and IgG antibodies specific for SARS-CoV-2. Noninformative priors were used. A sensitivity analysis was conducted considering three methods: 1) reverse transcription-polymerase chain reaction test (RT-PCR) as the gold standard, 2) BLCM with RT-PCR as an imperfect gold standard, and 3) frequentist latent class model (LCM). All analyses used software R version 4.3.0, and BLCM were fitted using package runjags using the software JAGS (Just Another Gibbs Sampler). RESULTS: The BLCM-derived sensitivity for IgM varied from 10.7% [95% credibility interval (CrI):1.9-24.6] to 96.9% (95% CrI: 91.0-100.0), with specificities ranging from 48.3% (95% CrI: 39.0-57.6) to 98.9% (95% CrI: 96.2-100.0). Sensitivity for IgG varied between 76.9% (95% CrI: 68.2-84.7) and 99.1% (95% CrI: 96.1-100.0), and specificity ranged from 49.9% (95% CrI: 19.4-95.8) to 99.3% (95% CrI: 97.2-100.0). LCM results were comparable to BLCM. Considering the RT-PCR as a gold standard underestimated the tests' sensitivity, particularly for IgM. CONCLUSION: BLCM-derived results deviated from those using a gold standard, which underestimated the tests' characteristics, particularly sensitivity. Although Bayesian and frequentist LCM approaches yielded comparable results, BLCM had the benefit of enabling credibility interval computation even when sample power is limited.

Advancing Toxoplasma gondii multiplex serology.

Toxoplasma gondii is a highly prevalent pathogen causing zoonotic infections with significant public health implications. Yet, our understanding of long-term consequences, associated risk factors, and the potential role of co-infections is still limited. Seroepidemiological studies are a valuable approach to address open questions and enhance our insights into T. gondii across human populations. Here, we present substantial advancements to our previously developed T. gondii multiplex serology assay, which is based on the immunodominant antigens SAG1 and P22. While our previous bead-based assay quantified antibody levels against multiple targets in a high-throughput fashion requiring only a small sample volume, impaired assay characteristics emerged in sample dilutions beyond 1:100 and when being transferred to magnetic beads. Both are now critical for inclusion in large-scale seroprevalence studies. Using the truncated versions, SAG1D1 and P22trunc, significantly enhanced signal-to-noise ratios were achieved with almost perfect concordance with the gold-standard Sabin-Feldman dye test. In sample dilutions of 1:100, the diagnostic accuracy of SAG1D1 and P22trunc reached sensitivities (true positive rates) of 98% and 94% and specificities (true negative rates) of 93% and 95%, respectively. Importantly, performance metrics were reproducible in a 1:1,000 sample dilution, using both magnetic and nonmagnetic beads. Thresholds for seropositivity were derived from finite mixture models and performed equally well as thresholds by receiver operating characteristic analysis. Our improved multiplex serology assay is therefore able to generate robust and reproducible performance metrics under various assay conditions. Inclusion of T. gondii antibody measurements with other pathogens, in multiplex serology panels will allow for large-scale seroepidemiological research. IMPORTANCE: Toxoplasma gondii is a pathogen of significant public health concern due to its widespread prevalence and zoonotic potential. However, our understanding of key aspects, such as risk factors for infection and disease, potential outcomes, and their trends, remains limited. Seroepidemiological studies in large cohorts are invaluable for addressing these questions but remain scarce. Our revised multiplex serology assay equips researchers with a powerful tool capable of delivering T. gondii serum antibody measurements with high sensitivity and specificity under diverse assay conditions. This advancement paves the way for the integration of T. gondii antibody measurements into multi-pathogen multiplex serology panels, promising valuable insights into public health and pathogen interactions.

Prevalence of neutralizing antibodies against SARS-CoV-2 using a rapid serological test in health workers of a Spanish Department of Health in Alicante (Spain) before the booster dose of the vaccine.

AIM: To study the prevalence of neutralizing antibodies in healthcare workers and healthcare support personnel after the administration of the second dose of the BNT162b2 vaccine (Pfizer-BioNTech). MATERIALS AND METHODS: In December 2021, we undertook a study in the Health Department in Orihuela, Alicante (Spain), which consists of 1500 workers. We collected demographic variables about the study participants, and we performed a "point-of-care" immunochromatography test to measure the presence of neutralizing antibodies (OJABIO® SARS-CoV-2 Neutralizing Antibody Detection Kit, manufactured by Wenzhou OJA Biotechnology Co., Ltd. Wenzhou, Zhejiang, China) before the administration of the third dose of the vaccine. RESULTS: We obtained complete information about 964 (64%) workers, which consisted of 290 men and 674 women. The average age was 45,8 years (min. 18, max. 68) and the average time since the last dose of the vaccine was 40,5 weeks (min. 1,71, max. 47,71). A total of 131 participants (13,5%) had suffered infection by SARS-CoV-2 confirmed using RT-PCR. The proportion of participants who showed presence of neutralizing antibodies was 38,5%. In the multivariable analysis, the time since the last dose of the vaccine (aOR week: 1,07; 95%CI: 1,04; 1,09) and previous infection by SARS-CoV-2 (aOR: 3,7; 95CI: 2,39; 5,63) showed a statistically significant association with the presence of neutralizing antibodies. CONCLUSIONS: The time since the administration of the last dose of the vaccine and the previous infection by SARS-CoV-2 determined the presence of neutralizing antibodies in 38,5% of the healthcare workers and support workers.

The importance of using WHO International Standards to harmonise SARS-CoV-2 serological assays.

The COVID-19 pandemic led to the rapid development of tests to diagnose SARS-CoV-2 infection and ascertain the prevalence of infection, along with the formulation of various treatments and vaccines. Globally, over 220 anti-SARS-CoV-2 serological assays have been developed for laboratory use, and many of these assays are currently used to assess immune responses against SARS-CoV-2. However, because these assays were independently developed by different manufacturers with different target antigens, immunoglobulin detection, technologies, and data reporting approaches, the results are not directly comparable, making it challenging to draw conclusions regarding immune responses at the population level. With deficiencies in assay validation, standardisation, and harmonisation, the inability to use and compare large datasets is becoming a major issue as serological data continue to increase. To help in addressing this issue, WHO established the first International Standard for the anti-SARS-CoV-2 immunoglobulin in late 2020. In this Personal View, we define the WHO International Standard for the anti-SARS-CoV-2 immunoglobulin, summarise the uses of primary versus secondary serology standards, recommend the use of such standards for data harmonisation, and list guidance and resources for using serology standards to improve data comparability.

Comparison of influenza viral load in nasopharyngeal and midturbinate swabs.

Different specimen types are used for influenza diagnosis but comparative data for viral loads from different swab types are limited. We compared influenza viral loads (determined by quantitative reverse transcription polymerase chain reaction [RT-PCR]) in 93 paired midturbinate and nasopharyngeal swab aliquots from influenza infected patients enrolled in a phase 3 randomized-controlled study with the objective of maximizing the number of swabs available for sequence analysis. Midturbinate swabs yielded a 53% lower viral load versus nasopharyngeal swabs, and this difference was similar for influenza A and B. These data suggest that nasopharyngeal swabs might be preferred in diagnostic settings when obtaining higher viral load is important.

Multicentric evaluation of sensitivity of eight commercial anti-SARS-CoV-2 antibody assays and their correlation to virus neutralization titers in seropositive subjects.

Diagnosis of SARS-CoV-2 virus is mainly based on direct detection. Determination of specific antibodies has been used mostly for epidemiological reasons. However, select immunoassays showed good correlation to plaque reduction virus neutralization test (PRNT) in smaller patient cohorts, which suggests their potential as predictors of virus neutralization titer. A total of 3,699 samples from Covid-19 patients were included in the multicentric study performed in the Czech Republic. Anti-SARS-CoV-2 antibody levels were evaluated by 8 commercial antibody assays. Simultaneously, PRNT evaluations were performed with the SARS-CoV-2 B.1.258 variant. All immunoassays showed an overall high true positive diagnostic value ranging from 79.17 to 98.04%. Several commercial EIA methods showed highly positive correlation between the assay results and PRNT levels, e.g., Liaison CoV-2 TrimericS IgG DiaSorin (Spearman r = 0.8833; Architect SASRS-CoV-2 IgG Abbott (r = 0.7298); NovaLisa SARS-CoV-2 IgG NovaTec (r = 0.7103) and Anti-SARS-CoV-2 ELISA IgG Euroimmun (r = 0.7094). While this correlation was less positive for other assays, those, conversely, presented higher true positive values. For most immunoassays, the positive percent agreement of the results was ≥ 95% in sera exhibiting PRNT levels of 1:80 and higher. The assays tested have shown variable correlation to PRNT. Those possessing high positive predictive values serve well as qualitative tests, while others can be utilised as quantitative tests highly predictive of neutralization antibody levels.