Sociodemographic and clinical characteristics associated with maternal and congenital syphilis - A prospective study in Peru

OBJECTIVES

The objective of this study was to explore the factors and outcomes associated with gestational syphilis in Peru.

METHODS

Women from the miscarriage, vaginal delivery, and C-section wards from a large maternity hospital in Lima with or without syphilis diagnosis were enrolled and their pregnancy outcomes compared. Maternal syphilis status using maternal blood and child serostatus using cord blood were determined by rapid plasma reagin (RPR) and rapid syphilis tests. The newborns' clinical records were used to determine congenital syphilis.

RESULTS

A total of 340 women were enrolled, 197 were positive and 143 were negative for RPR/rapid syphilis tests. Antibody titers in sera from cord and maternal blood were comparable with RPR titers and were highly correlated (rho = 0.82, P <0.001). Young age (P = 0.009) and lower birth weight (P = 0.029) were associated with gestational syphilis. Of the women with gestational syphilis, 76% had received proper treatment. Mothers of all newborns with congenital syphilis also received appropriate treatment. Treatment of their sexual partners was not documented.

CONCLUSIONS

Syphilis during pregnancy remains a major cause of the fetal loss and devastating effects of congenital syphilis in newborns.

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.

A novel Bayesian Latent Class Model (BLCM) evaluates multiple continuous and binary tests: A case study for Brucella abortus in dairy cattle

Bovine brucellosis, primarily caused by Brucella abortus, severely affects both animal health and human well-being. Accurate diagnosis is crucial for designing informed control and prevention measures. Lacking a gold standard test makes it challenging to determine optimal cut-off values and evaluate the diagnostic performance of tests. In this study, we developed a novel Bayesian Latent Class Model that integrates both binary and continuous testing outcomes, incorporating additional fixed (parity) and random (farm) effects, to calibrate optimal cut-off values by maximizing Youden Index. We tested 651 serum samples collected from six dairy farms in two regions of Henan Province, China with four serological tests: Rose Bengal Test, Serum Agglutination Test, Fluorescence Polarization Assay, and Competitive Enzyme-Linked Immunosorbent Assay. Our analysis revealed that the optimal cut-off values for FPA and C-ELISA were 94.2 mP and 0.403 PI, respectively. Sensitivity estimates for the four tests ranged from 69.7% to 89.9%, while specificity estimates varied between 97.1% and 99.6%. The true prevalences in the two study regions in Henan province were 4.7% and 30.3%. Parity-specific odds ratios for positive serological status ranged from 1.2 to 2.2 for different parity groups compared to primiparous cows. This approach provides a robust framework for validating diagnostic tests for both continuous and discrete tests in the absence of a gold standard test. Our findings can enhance our ability to design targeted disease detection strategies and implement effective control measures for brucellosis in Chinese dairy farms.

Use of recombinant malate dehydrogenase (MDH) and superoxide dismutase (SOD) [CuZn] as antigens in indirect ELISA for diagnosis of bovine brucellosis

The objective of this study was to validate an indirect enzyme-linked immunoassay (iELISA) using the recombinant proteins, malate dehydrogenase (MDH) and superoxide dismutase (SOD) [CuZn], as antigens and to evaluate its ability to discriminate antibodies produced by vaccination from those induced by infection in the diagnosis of bovine brucellosis. Sera from six groups were evaluated: G1 - culture-positive animals (52 serum samples) (naturally infected); G2 - non-vaccinated animals (28 serum samples) positive in RBT (Rose Bengal test) and 2ME (2-mercaptoethanol test) selected from brucellosis-positive herds; G3 - animals from a brucellosis-free area (32 serum samples); G4 - S19 vaccinated heifers (114 serum samples); G5 - RB51 vaccinated heifers (60 serum samples); G6 - animals inoculated with inactivated Yersinia enterocolitica O:9 (42 serum samples). Diagnostic sensitivity (DSe) and diagnostic specificity (DSp) were estimated using the frequentist approach and the confidence interval (CI) (95%) calculated by the Clopper-Pearson (exact) method. The DSe for iELISA_MDH in the G1 group was 71.7% (CI 95%: 57.6-83.2%) and for the G2 100.0% (CI 95%: 87.7-100.0%), whereas the DSp was 84.4% in the G3 (CI 95%: 67.2-94.7%). For the iELISA_SOD the DSe was estimated 67.3% for the G1 (CI 95%: 52.9-79.7%) and 71.4% for G2 (CI 95%: 51.3-86.8%), while the DSp for G3 was 87.5% (CI 95%: 71.0-96.5%). iELISA_MDH and iELISA_SOD showed potential to be used in the diagnosis of infected animals, increasing the range of serological tests available for the diagnosis of bovine brucellosis, with the advantage of being S-LPS-free. However, none of the tests could differentiate between infection and vaccination.

Performance evaluation of in-house developed Covid-19 IgG/IgM antibody rapid diagnostic kit

In the interest of preventing the Coronavirus Disease 2019 (COVID-19) pandemic from spreading, it is crucial to promptly identify and confine afflicted patients. Serological antibody testing is a significant diagnostic technique that is increasingly employed in clinics, however its clinical use is still being investigated. The present study was carried out to scrutinize how well Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) antibody testing using in-house developed rapid antibody assay worked against the chemiluminescence (CLIA) assay. Either IgG positive (IgG + IgM-) or IgM positive (IgM + IgG-); both IgG and IgM positive (IgM + IgG+); and negatives (IgM- IgG-) have been evaluated. A total of 300 samples with diverse age and sexual identity data were included. The combined sensitivities for IgG + IgM+, IgM + IgG-, IgG + IgM- and IgG-IgM- were evaluated. More accurate diagnostic results may be obtained using molecular diagnostic tools. The Antibody Rapid Diagnostic kit's (in-house developed) performance was satisfactory for determining the presence of Covid-19 infection with IgG and IgM positivity. The IgG and IgM positivity helped evaluate the immune response in the individual for the COVID-19 infection. These results lend support to the additional utilisation of serological antibody tests in the COVID-19 diagnosis.

Assessment of the diagnostic performance of serological tests in areas where Leishmania infantum and Leishmania tarentolae occur in sympatry

BACKGROUND

Visceral leishmaniosis caused by infection with the zoonotic protozoan Leishmania infantum is a life-threatening disease affecting dogs and humans. The sympatric occurrence of L. infantum and Leishmania tarentolae in an area of southern Italy endemic for canine leishmaniosis, where dogs are also exposed to the latter species, suggests the persistence of herpetophilic L. tarentolae in a non-permissive host, therefore raising questions about the performance of serological diagnostic tests routinely employed.

METHODS

The diagnostic performance of serological tests such as the immunofluorescence antibody test (IFAT), two commercial immunoenzymatic assays (i.e. NovaTec VetLine Leishmania ELISA® and rK39 ICT®) and an in-house enzyme-linked immunosorbent assay (ELISA) was evaluated in healthy dogs seropositive to L. infantum, whereas the only IFAT available was used to detect antibodies to L. tarentolae.

RESULTS

With the IFAT, out of a total of 104 dogs tested, 15 were seronegative for L. infantum of which three were L. tarentolae seropositive' and 89 were L. infantum seropositive. Of the latter 89 dogs, representing the highest proportion of seropositive animals (85.6%) detected by IFAT' 66 were also seropositive for L. tarentolae. Cohen's kappa (κ) agreement coefficient between the IFAT results and those of all the other tests was very low, and the IFAT results were significantly different from those of all the other serological tests as calculated by Cochran's Q-test. Analysis using the Bayesian latent class (Bayes-LCA) showed that the in-house ELISA and IFAT contributed the most towards identifying infected and non-infected dogs, respectively. The IFAT test showed low positive predictive value (59.5%), but high negative predictive value (100%).

CONCLUSIONS

These results demonstrate that the IFAT for L. infantum, although highly sensitive, may not be considered a useful diagnostic test due to its low specificity. Therefore, an accurate serological tool with high specificity is mandatory for avoiding cross-reaction in epidemiological contexts where the two species of Leishmania occur in sympatry.

Peptide microarray analysis of in-silico predicted B-cell epitopes in SARS-CoV-2 sero-positive healthcare workers in Bulawayo, Zimbabwe

Immunogenic peptides that mimic linear B-cell epitopes coupled with immunoassay validation may improve serological tests for emerging diseases. This study reports a general approach for profiling linear B-cell epitopes derived from SARS-CoV-2 using an in-silico method and peptide microarray immunoassay, using healthcare workers' SARS-CoV-2 sero-positive sera. SARS-CoV-2 was tested using rapid chromatographic immunoassays and real-time reverse-transcriptase polymerase chain reaction. Immunogenic peptides mimicking linear B-cell epitopes were predicted in-silico using ABCpred. Peptides with the lowest sequence identity with human protein and proteins from other human pathogens were selected using the NCBI Protein BLAST. IgG and IgM antibodies against the SARS-CoV-2 spike protein, membrane glycoprotein and nucleocapsid derived peptides were measured in sera using peptide microarray immunoassay. Fifty-three healthcare workers included in the study were RT-PCR negative for SARS-CoV-2. Using rapid chromatographic immunoassays, 10 were SARS-CoV-2 IgM sero-positive and 7 were SARS-CoV-2 IgG sero-positive. From a total of 10 SARS-CoV-2 peptides contained on the microarray, 3 (QTH34388.1-1-14, QTN64908.1-135-148, and QLL35955.1-22-35) showed reactivity against IgG. Three peptides (QSM17284.1-76-89, QTN64908.1-135-148 and QPK73947.1-8-21) also showed reactivity against IgM. Based on the results we predicted one peptide (QSM17284.1-76-89) that had an acceptable diagnostic performance. Peptide QSM17284.1-76-89 was able to detect IgM antibodies against SARS-CoV-2 with area under the curve (AUC) 0.781 when compared to commercial antibody tests. In conclusion in silico peptide prediction and peptide microarray technology may provide a platform for the development of serological tests for emerging infectious diseases such as COVID-19. However, we recommend using at least three in-silico peptide prediction tools to improve the sensitivity and specificity of B-cell epitope prediction, to predict peptides with excellent diagnostic performances.

Celiac Disease Revisited

Celiac disease (CD) is a systemic disease triggered by gluten ingestion in genetically predisposed individuals. It manifests primarily as an autoimmune enteropathy associated with specific circulating autoantibodies and a human leukocyte antigen haplotype (HLA-DQ2 or HLA-DQ8). It afflicts roughly 1% of the population, though the majority of patients remain undiagnosed. Diarrhea and malabsorption are classic manifestations of CD; however, both children and adults can be paucisymptomatic and present extraintestinal manifestations such as anemia, osteoporosis, and abnormal liver tests. CD screening is not recommended for the general population, and it should be focused on high-risk groups. CD diagnosis is challenging and relies on serological tests, duodenal histology, and genetic testing. Particularly difficult presentations to manage are seronegative patients, seropositive patients without villus atrophy, and patients who have started a gluten-free diet before the diagnostic workup. The only proven treatment is a lifelong gluten-free diet. We present an in-depth review on the physiopathology and management of CD, with a particular emphasis on diagnostic challenges.

SARS-CoV2 infection in symptomatic patients: interest of serological tests and predictors of mortality: experience of DR Congo

Background

In symptomatic patients, the diagnostic approach of COVID-19 should be holistic. We aimed to evaluate the concordance between RT-PCR and serological tests (IgM/IgG), and identify the factors that best predict mortality (clinical stages or viral load).

Methods

The study included 242 patients referred to the University hospital of Kinshasa for suspected COVID-19, dyspnea or ARDS between June 1st, 2020 and August 02, 2020. Both antibody-SARS-CoV2 IgM/IgG and RT-PCR method were performed on the day of admission to hospital. The clinical stages were established according to the COVID-19 WHO classification. The viral load was expressed by the CtN2 (cycle threshold value of the nucleoproteins) and the CtE (envelope) genes of SARS- CoV-2 detected using GeneXpert. Kappa test and Cox regression were used as appropriate.

Results

The GeneXpert was positive in 74 patients (30.6%). Seventy two patients (29.8%) had positive IgM and 34 patients (14.0%) had positive IgG. The combination of RT-PCR and serological tests made it possible to treat 104 patients as having COVID-19, which represented an increase in cases of around 41% compared to the result based on GeneXpert alone. The comparison between the two tests has shown that 57 patients (23.5%) had discordant results. The Kappa coefficient was 0.451 (p < 0.001). We recorded 23 deaths (22.1%) among the COVID-19 patients vs 8 deaths (5.8%) among other patients. The severe-critical clinical stage increased the risk of mortality vs. mild-moderate stage (aHR: 26.8, p < 0.001). The values of CtE and CtN2 did not influence mortality significantly.

Conclusion

In symptomatic patients, serological tests are a support which makes it possible to refer patients to the dedicated COVID-19 units and treat a greater number of COVID-19 patients. WHO Clinical classification seems to predict mortality better than SARS-Cov2 viral load.

In-silico design of a multi-epitope for developing sero-diagnosis detection of SARS-CoV-2 using spike glycoprotein and nucleocapsid antigens

COVID-19 is a pandemic disease caused by novel corona virus, SARS-CoV-2, initially originated from China. In response to this serious life-threatening disease, designing and developing more accurate and sensitive tests are crucial. The aim of this study is designing a multi-epitope of spike and nucleocapsid antigens of COVID-19 virus by bioinformatics methods. The sequences of nucleotides obtained from the NCBI Nucleotide Database. Transmembrane structures of proteins were predicted by TMHMM Server and the prediction of signal peptide of proteins was performed by Signal P Server. B-cell epitopes' prediction was performed by the online prediction server of IEDB server. Beta turn structure of linear epitopes was also performed using the IEDB server. Conformational epitope prediction was performed using the CBTOPE and eventually, eight antigenic epitopes with high physicochemical properties were selected, and then, all eight epitopes were blasted using the NCBI website. The analyses revealed that α-helices, extended strands, β-turns, and random coils were 28.59%, 23.25%, 3.38%, and 44.78% for S protein, 21.24%, 16.71%, 6.92%, and 55.13% for N Protein, respectively. The S and N protein three-dimensional structure was predicted using the prediction I-TASSER server. In the current study, bioinformatics tools were used to design a multi-epitope peptide based on the type of antigen and its physiochemical properties and SVM method (Machine Learning) to design multi-epitopes that have a high avidity against SARS-CoV-2 antibodies to detect infections by COVID-19.

An outlook on coronavirus disease 2019 detection methods

Diagnostic testing plays a fundamental role in the mitigation and containment of coronavirus disease 2019 (COVID-19), as it enables immediate quarantine of those who are infected and contagious and is essential for the epidemiological characterization of the virus and estimating the number of infected cases worldwide. Confirmation of viral infections, such as COVID-19, can be achieved through two general approaches: nucleic acid amplification tests (NAATs) or molecular tests, and serological or antibody-based tests. The genetic material of the pathogen is detected in NAAT, and in serological tests, host antibodies produced in response to the pathogen are identified. Other methods of diagnosing COVID-19 include radiological imaging of the lungs and in vitro detection of viral antigens. This review covers different approaches available to diagnosing COVID-19 by outlining their advantages and shortcomings, as well as appropriate indications for more accurate testing.

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Diagnostic tests to detect coronavirus disease 2019 (COVID-19).

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Advantages and disadvantages associated with each detection method.

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Implications for a more accurate and rapid testing of COVID-19 or other similar future emergent viruses.

Exudative pleural effusion caused by lung fluke infection: case report

The global incidence of lung fluke disease is low, and the infection is a rare cause of pleural effusion in adults. This article reports a case of exudative pleural effusion accompanied by eosinophilia in a 19-year-old male which was finally proven to be caused by lung fluke infection through antibody testing. This case highlights that lung fluke infection is an easily overlooked cause of pleural effusion. Eosinophilia is a potential marker of infection, and serological tests could further confirm the diagnosis.

Telemedicine follow-ups for COVID-19: Experience in a tertiary hospital

INTRODUCTION

Telemedicine is an attractive option for the follow-up of paediatric patients with SARS-CoV-2 infection. The aim of this article is to describe the experience with telephone consultations in a tertiary hospital.

PATIENTS AND METHODS

Retrospective descriptive study of children with confirmed or probable diagnosis of COVID-19 attended by telephone consultations in Hospital La Paz (Madrid) between March and June 2020. Patients were referred from the Emergency Department after being discharged from the hospital. Telephone consultations were made every 48 h until symptoms resolved, then weekly until completing 14 days without symptoms.

RESULTS

A total of 72 children were included, with median age of 83.5 months [IQR = 16.3-157.5]. Of those 46 (63.9%) were male, and 14 (19.4%) had comorbidities. There were 32 (44.4%) hospital admissions. COVID-19 diagnosis was confirmed in 33 children by RT-PCR, and in 7 by serology tests. The seroconversion rate was 67.7% in those patients with a positive RT-PCR. Other infections were found in 7 patients (5 Mycoplasma pneumoniae, 1 parvovirus, and 1 CMV). Median symptom duration was 25.5 days [IQR = 13.8-37], while median follow-up duration was 28 days [IQR = 21-39]. The median number of telephone consultations per patient was 6 [IQR = 4-8]. Clinical worsening was reported in 19 (26.4%) during follow-up, and 14 (19.4%) were re-evaluated in the Emergency Department. One patient required hospital admission, but he had a favourable outcome.

CONCLUSIONS

Children with suspected SARS-CoV-2 infection should be followed-up due to prolonged duration of symptoms, and the risk of clinical deterioration. Telephone consultations are a useful and safe alternative for the follow-up of patients with mild symptoms, and for children discharged from the hospital.

The WHO International Standard for COVID-19 serological tests: towards harmonization of anti-spike assays

BACKGROUND AND AIMS

SARS-CoV-2 antibody assays are relevant in managing the COVID-19 pandemic, providing valuable data on the immunization status of the population. However, current serology tests are highly variable, due to their different characteristics and to the lack of reference materials. The aim of the World Health Organization (WHO) first International Standard (IS) for anti-SARS-CoV-2 immunoglobulin is to harmonize humoral immune response assessment after natural infection or vaccination, and recommend reporting the results for binding activity in Binding Antibody Units (BAU).

MATERIALS AND METHODS

This study analyzed six commercial quantitative anti-SARS-CoV-2 S-protein assays in a head-to-head comparison, using the manufacturers' conversion factors for the WHO IS to obtain BAU/mL values.

RESULTS

Our data showed good alignment up to 1000 BAU/mL, then began to disperse, exhibiting some discrepancies. Moreover, correlations among methods varied with Cohen's Kappa ranging from 0.580 to 1.00, with the lowest agreement values for kits using different target antigens or different antibody isotypes, making it clear that the laboratory report should include this information. Values expressed as BAU/ml showed a reduced between-assays variability compared to AU/ml (median coefficients of variation 0.38 and 0.68, respectively; p < 0.001).

CONCLUSION

On the basis of these data at present anti-SARS CoV-2 serological assays' results are not interchangeable, and, more importantly, individual immune monitoring should be performed with the same method.

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

OBJECTIVE

In vitro diagnostic tests for SARS-COV-2, also known as serological tests, have rapidly spread. However, to date, mostly single-center technical and diagnostic performance's assessments have been carried out without an intralaboratory validation process and a health technology assessment (HTA) systematic approach. Therefore, the rapid HTA for evaluating antibody tests for SARS-COV-2 was applied.

METHODS

The use of rapid HTA is an opportunity to test innovative technology. Unlike traditional HTA (which evaluates the benefits of new technologies after being tested in clinical trials or have been applied in practice for some time), the rapid HTA is performed during the early stages of developing new technology. A multidisciplinary team conducted the rapid HTA following the HTA Core Model® (version 3.0) developed by the European Network for Health Technology Assessment.

RESULTS

The three methodological and analytical steps used in the HTA applied to the evaluation of antibody tests for SARS-COV-2 are reported: the selection of the tests to be evaluated; the research and collection of information to support the adoption and appropriateness of the technology; and the preparation of the final reports and their dissemination. Finally, the rapid HTA of serological tests for SARS-CoV-2 is summarized in a report that allows its dissemination and communication.

CONCLUSIONS

The rapid-HTA evaluation method, in addition to highlighting the characteristics that differentiate the tests from each other, guarantees a timely and appropriate evaluation, becoming a tool to create a direct link between science and health management.

Evaluation of S-RBD and high specificity ACE-2-binding antibodies on SARS-CoV-2 patients after six months from infection

The antibody response to SARS-CoV-2 has not yet fully defined, but the availability of sensitive and specific serological assays is crucial to observe the presence of specific antibodies against the human receptor binding domain (S-RBD) and high specificity ACE-2-binding antibodies or neutralizing antibodies (NT) in response to vaccines. Indeed, these peculiar antibodies should prevent viral interaction between RBD and Angiotensin-Converting Enzyme 2 (ACE2) receptor, located on surface of host cells. In this study, 72 samples from 37 hospitalized COVID-19 patients and 35 not-hospitalized patients were analyzed longitudinally. The detection of S-RBD and NT antibodies was carried out using CLIA tests.

Hospitalized patients showed elevated serum levels of S-RBD (97.22%) and NT (77.78%) antibodies, differently, not-hospitalized, who were paucisymptomatic or asymptomatic patients, showed lower serum levels of S-RBD (65.71%) and NT (38.14%) antibodies.

The results suggest that the NT serum level is strongly related to disease severity (p < 0.001) and to the serum level of S-RBD antibodies (p < 0.0001).

Comparison of serological and molecular techniques to detect Toxoplasma gondii in free-range chickens (Gallus gallus domesticus)

The present study aimed to compare different indirect and direct diagnostic techniques to diagnose Toxoplasma gondii in free-range chickens. Samples of 386 chickens obtained from 24 Paraná properties were used for serological analysis by indirect fluorescent antibody test (IFAT), modified agglutination test (MAT), and enzyme-linked immunosorbent assay (ELISA). Animals positive by IFAT and/or MAT had their tissues submitted to the mouse bioassay, and those who were positive in this technique had their blood, tissues, and acidic pepsin tissue digestion submitted to PCR (conventional, nested, and quantitative-PCR (qPCR)). One hundred and nineteen chickens (30.8 %) were positive in at least one of the serological tests, being 102 (26.4 %) in the IFAT, 64 (16.6 %) in the MAT, and 62 (16.0 %) in the ELISA. The IFAT was used as a gold standard, and the MAT showed higher sensitivity (46.0 %) and specificity (94.0) compared to ELISA (43.5 % and 93.6 %, respectively). Ninety samples of eighteen chickens positive in the mouse bioassay were subjected to PCR, and according to molecular tests, the conventional PCR detected the T. gondii DNA in 30 % (27/90) of the samples, in 38.8 % (35/90) with nested-PCR and 40.0 % (36/90) with real-time. According to molecular analyzes, the sensitivity was higher in ITS1 nested-PCR (69.4 %) and specificity in conventional PCR-529bp (90.7 %), using the qPCR as the gold standard. MAT and ELISA had similarities in concordance analyzes. The IFAT was the serological technique with the highest agreement with the mouse bioassay, and serological tests in parallel showed to be a good screening option for the isolation of T. gondii in chick tissues. The PCR markers effectively detected the parasite DNA, and the heart was the tissue with the highest number of positives samples. The conventional PCR had sensitivity similar to nested-PCR and qPCR and could be a cheaper alternative to diagnose T. gondii infection in chicken tissues.

Comparison of hemagglutination inhibition tests, immunoperoxidase monolayer assays, and serum neutralizing tests in detecting antibodies against blue eye disease in pigs

Blue eye disease (BED) of pigs was identified in the early 1980s in La Piedad, Michoacan, Mexico. The causal agent is Porcine orthorubulavirus (PRV), which affects pigs of all ages, producing nervous, respiratory, and reproductive disorders. BED is geographically endemic to the center of Mexico, where 75% of the country's swine industry is concentrated. Due to its adverse effects on the swine industry and the risk of dissemination to other countries, it is essential to have reliable diagnostic methods for BED. The objective of this study was to establish the optimal conditions for three serological tests, hemagglutination inhibition (HI), immunoperoxidase monolayer assay (IPMA), and serum neutralization (SN), and to compare their sensitivity, specificity, kappa coefficient, and predictive values. Twelve different HI protocols (9408 tests), one SN protocol and one IPMA protocol (784 tests, each) were evaluated. Forty-nine sera were analyzed, and thirty-seven sera showed true positive results, while twelve showed true negative results. The kappa coefficient was used to assess the variation in each test. The best HI protocol registered a sensitivity and specificity of 89 and 100%, respectively, the IPMA test showed values of 85 and 100%, and the SN test registered a sensitivity of 91% and a specificity of 96%. One of the disadvantages of the HI test is that when chicken red blood cells (RBCs) are used, elution occurs in a short incubation time, which would decrease the specificity. The use of bovine RBCs increases the specificity of the testy and makes it more stable, but it decreases the sensitivity. The results of HI and SN revealed the importance of eliminating the complement system of the serum and removing other inhibitors to avoid test nonspecificity. The IPMA test does not use an active virus; hence, it is considered safe and does not present any risk of disseminating PRV.

Performance assessment of 11 commercial serological tests for SARS-CoV-2 on hospitalised COVID-19 patients

BACKGROUND

Commercial availability of serological tests to evaluate immunoglobulins (Ig) targeting severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has grown exponentially since the start of the coronavirus disease 2019 (COVID-19) outbreak. Thorough validation of these tests is important before use as epidemiological tools to infer seroprevalence in specific populations and as diagnostic tools to complement molecular approaches (e.g., quantitative reverse transcription-polymerase chain reaction).

METHODS

Commercial serological tests from 11 suppliers were assayed side-by-side using 126 samples from SARS-CoV-2-infected inpatients and 36 from healthy and HIV-infected individuals.

RESULTS

The majority of the tests assayed have >95% specificity. For the sensitivity calculation, samples were stratified by days since symptoms onset; sensitivity peaks at 16-21 days for IgM and IgA (maximum 91.2%, Euroimmun) and, dependant on the test, at 16-21 or >21 days for IgG (maximum 94.1%, Snibe). Data from semiquantitative tests show that patients with a severe clinical presentation have lower levels of Ig targeting SARS-CoV-2 at <10 days since symptoms onset and higher levels at >21 days, compared to patients with a non-severe presentation.

CONCLUSIONS

This study highlights the heterogeneity of sensitivity and generally high specificity of the serological tests and establishes a basis for their usefulness to complement diagnostic techniques and population seroprevalence studies.

A low-cost initiative to reduce duplicate hepatitis B virus serological testing

Background

Currently, multiple clinical laboratories provide serological testing for hepatitis B virus (HBV) in Alberta, Canada. Concerns were raised regarding single serology specimens having duplicate testing performed during the specimen referral process from one laboratory to another. In an attempt to reduce duplicate testing for anti-HBs and HBsAg markers, we implemented a stamp on paper requisitions to identify if testing had already been performed on referred specimens. We aimed to determine the number of duplicate tests and cost of duplicate testing pre- and post-stamp implementation.

Study design

The requisition stamp was implemented between May and August 2016. HBV serology testing results from two clinical laboratories between January 01, 2015 and December 31, 2017 (n ​= ​803,637) were examined. The number of tests performed on the same individual within a 3-day window was identified and the associated costs were determined.

Results

After stamp implementation, duplicated HBsAg and anti-HBs tests decreased from 20.8% (n ​= ​28,545) and 18.4% (n ​= ​20,151) to 3.7% (n ​= ​4,604) and 2.5% (n ​= ​2,593), respectively. This represented an estimated annual savings of $86,427 and $82,522 CAD in supply costs for HBsAg and anti-HBs tests, respectively.

Conclusions

The requisition stamp initiative was effective in reducing the number of duplicate tests performed between two laboratory sites. This low-cost intervention could be applied to other testing situations, including other highly duplicated serological markers, which may have broad reaching cost-saving effects for laboratory testing.

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We describe a low-cost, low-tech method to reduce duplicate serology testing.

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We decreased redundant testing from 20% to 3% among all HBsAg and anti-HBs testing.

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Applying this strategy to other high-volume tests could realize significant savings.

False-positive results of SARS-CoV-2 IgM/IgG antibody tests in sera stored before the 2020 pandemic in Italy

OBJECTIVES

Aside from the outbreak of the coronavirus disease 2019 (COVID-19), serological tests are not well known for their diagnostic value. We assessed the performance of serological tests using stored sera from patients with a variety of pathologic conditions, collected before the 2020 pandemic in Italy.

METHODS

Rapid lateral flow tests and Enzyme-Linked Immunosorbent Assays (ELISA) that detect Immunoglobulin M (IgM) and Immunoglobulin G (IgG) antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were carried out using 1150 stored human serum samples that had been collected in 2018 and 2019. The tests were also run using samples from 15 control patients who had positive or negative oral swab test results, as assessed using real-time reverse transcription-polymerase chain reaction (rRT-PCR). The urea dissociation test was employed to rule out false-positive reactivity in the two antibody detection methods.

RESULTS

The lateral flow tests revealed 21 positive samples from the stored sera: 12 for IgM, four for IgG, and five for IgM/IgG. Among the nine rRT-PCR- positive controls, six individuals presented IgG and three IgM/IgG positivity. Using the urea (6 mol/L) dissociation test, two of the twelve stored samples that had shown IgM positivity were confirmed to be positive. The ELISA test detected four IgM-positive and three IgG-positive specimens. After treatment with 4 mol/L urea, the IgM-positive samples became negative, whereas the IgG positivity persisted. All of the rRT-PCR-positive controls were found to retain IgM or IgG positivity following the urea treatment.

CONCLUSIONS

Our findings highlight the limited utility of serological testing for the SARS-CoV-2 virus based on the results of specimens collected before the outbreak of the infection.

Serological determinants of COVID-19

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection spreaded rapidly worldwide, as far as it has become a global pandemic. Therefore, the introduction of serological tests for determination of IgM and IgG antibodies has become the main diagnostic tool, useful for tracking the spread of the virus and for consequently allowing its containment. In our study we compared point of care test (POCT) lateral flow immunoassay (FIA) vs automated chemiluminescent immunoassay (CLIA), in order to assess their specificity and sensibility for COVID-19 antibodies detection.

RESULTS

We find that different specificities and sensitivities for IgM and IgG tests. Notably IgM POCT FIA method vs CLIA method (gold standard) has a low sensitivity (0.526), while IgG POCT FIA method vs CLIA method (gold standard) test has a much higher sensitivity (0.937); further, with respect of IgG, FIA and CLIA could arguably provide equivalent information.

CONCLUSIONS

FIA method could be helpful in assessing in short time, the possible contagiousness of subjects that for work reasons cannot guarantee "social distancing".

[Telemedicine follow-ups for COVID-19: Experience in a tertiary hospital]

INTRODUCTION

Telemedicine is an attractive option for the follow-up of paediatric patients with SARS-CoV-2 infection. The aim of this article is to describe the experience with telephone consultations in a tertiary hospital.

PATIENTS AND METHODS

Retrospective descriptive study of children with confirmed or probable diagnosis of COVID-19 attended by telephone consultations in Hospital La Paz (Madrid) between March and June 2020. Patients were referred from the Emergency Department after being discharged from the hospital. Telephone consultations were made every 48hours until symptoms resolved, then weekly until completing 14 days without symptoms.

RESULTS

A total of 72 children were included, with median age of 83.5 months (IQR=16.3-157.5). Of those 46 (63.9%) were male, and 14 (19.4%) had comorbidities. There were 32 (44.4%) hospital admissions. COVID-19 diagnosis was confirmed in 33 children by RT-PCR, and in 7 by serology tests. The seroconversion rate was 67.7% in those patients with a positive RT-PCR. Other infections were found in 7 patients (5 Mycoplasma pneumoniae, 1 parvovirus, and 1 cytomegalovirus). Median symptom duration was 25.5 days (IQR=13.8-37), while median follow-up duration was 28 days (IQR=21-39). The median number of telephone consultations per patient was 6 (IQR=4-8). Clinical worsening was reported in 19 (26.4%) during follow-up, and 14 (19.4%) were re-evaluated in the Emergency Department. One patient required hospital admission, but he had a favourable outcome.

CONCLUSIONS

Children with suspected SARS-CoV-2 infection should be followed-up due to prolonged duration of symptoms, and the risk of clinical deterioration. Telephone consultations are a useful and safe alternative for the follow-up of patients with mild symptoms, and for children discharged from the hospital.

Clinically practiced and commercially viable nanobio engineered analytical methods for COVID-19 diagnosis

The recent outbreak of the coronavirus disease (COVID-19) has left the world clueless. As the WHO declares this new contagion as a pandemic on the 11th of March 2020, the alarming rate of the spawn of the disease in such a short period has disarranged the globe. Standing against this situation researchers are strenuously searching for the key traits responsible for this pandemic. As knowledge regarding the dynamics and host-path interaction of COVID-19 causing Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is currently unknown, the formulation of strategies concerning antiviral treatment, vaccination, and epidemiological control stands crucial. Before designing adequate therapeutic strategies, it is extremely essential to diagnose the disease at the outset as early detection can have a greater impact on building health system capacity. Hence, a comprehensive review of strategies for COVID-19 diagnosis is essential in this existing global situation. In this review, sequentially, we have provided the clinical details along with genetic and proteomic biomarkers related to COVID-19. The article systematically enlightens a clear overview of the clinically adopted techniques for the detection of COVID-19 including oligonucleotide-based molecular detection, Point-of-Care immunodiagnostics, radiographical analysis/sensing system, and newly developed biosensing prototypes having commercial viability. The commercial kits/analytical methods based-sensing strategies have also been tabulated categorically. The critical insights on the developer, commercial brand name, detection methods, technical operational details, detection time, clinical specimen, status, the limit of detection/detection ability have been discussed comprehensively. We believe that this review may provide scientists, clinicians and healthcare manufacturers valuable information regarding the most recent developments/approaches towards COVID-19 diagnosis.

Factors associated with leprosy in children contacts of notified adults in an endemic region of Midwest Brazil

OBJECTIVES

To analyze the factors associated with leprosy in children who were intradomiciliary contacts of notified adults with the disease in an endemic municipality in Mato Grosso, Brazil.

METHOD

Case-control study with 204 children under 15 years of age, living in an endemic municipality. Cases (n=40) were considered as the children with leprosy registered at the National Information System of Notifiable Diseases in 2014 and 2015, who were intradomiciliary contacts of at least one adult diagnosed with the disease in the family, and as a control group (n=164) of children living within a radius of up to 100m of the notified cases. Data were obtained through medical file analysis, interviews, and blood samples for anti-PGL-I serological test by the ELISA method. The binary logistic regression technique was used, with p≤0.05.

RESULTS

After adjustments, the following were associated with leprosy: age (95% CI: 1.24-9.39, p=0.018), area of residence (95% CI: 1.11-6.09, p=0.027), waste disposal (95% CI: 1.91-27.98, p=0.004), family history of the disease (95% CI: 3.41-22.50, p=0.000), and time of residence (95% CI: 1.45-7.78, p=0.005).

CONCLUSION

Factors associated with the disease indicate greater vulnerability of children aged 8-14 years, associated with living conditions and time of residence, as well as the family history of the disease.

The impact of biosensing in a pandemic outbreak: COVID-19

COVID-19 pandemic outbreak is the most astounding scene ever experienced in the XXI century. In this opinionated review, we underscore the crucial role of biosensing to handle with such situations. As a matter of fact, testing accelerates life-saving decisions on treatment and isolation of COVID-19 patients in an early stage, and thereby, decelerating or even preventing the spread of such emerging infectious diseases. Meanwhile, it is also proven that a timely and broad application of testing leads to lower mortality rates in countries like Germany or South Korea. Besides, biosensors are also powerful tools for effective assessment of clinical progress and to provide alertness on severity or critical trends of infection. In view hereof, we critically discuss the state-of-the-art biosensing devices for COVID-19 testing. We spot the urgent needs and highlight innovative diagnostic approaches for targeting various COVID-19 related biomarkers. Finally, we outline our recommendations on biosensors and biosensing-related issues towards pandemic outbreaks.

CT abnormalities evocative of lung infection are associated with lower 18F-FDG uptake in confirmed COVID-19 patients

PURPOSE

CT signs that are evocative of lung COVID-19 infections have been extensively described, whereas ¹⁸F-FDG-PET signs have not. Our current study aimed to identify specific COVID-19 ¹⁸F-FDG-PET signs in patients that were (i) suspected to have a lung infection based on ¹⁸F-FDG-PET/CT recorded during the COVID-19 outbreak and (ii) whose COVID-19 diagnosis was definitely established or excluded by appropriate viral testing.

METHODS

Twenty-two consecutive patients referred for routine ¹⁸F-FDG-PET/CT examinations during the COVID-19 outbreak (March 25th to May 15th 2020) and for whom CT slices were evocative of a lung infection were included in the study. All patients had undergone a SARS-COV-2 diagnostic test to confirm COVID-19 infection (positivity was based on molecular and/or serological tests) or exclude it (negativity of at least the serological test).

RESULTS

Eleven patients were confirmed to be affected by COVID-19 (COVID+), whereas the other eleven patients were not (COVID-) and were predominantly suspected of having bacterial pneumonia. CT abnormalities were not significantly different between COVID+ and COVID- groups, although trends toward larger CT abnormalities (p = 0.16) and lower rates of consolidation patterns (0.09) were observed in the COVID+ group. The maximal standardized uptake values (SUV_max) of lung areas with CT abnormalities were however significantly lower in the COVID+ than the COVID- group (3.7 ± 1.9 vs. 6.9 ± 4.1, p = 0.03), with the highest SUV_max consistently not associated with COVID-19.

CONCLUSION

Among CT abnormalities evocative of lung infection, those related to COVID-19 are associated with a more limited ¹⁸F-FDG uptake. This observation may help improve our ability to detect COVID-19 patients.

Comparison of serologic and molecular SARS-CoV 2 results in a large cohort in Southern Tuscany demonstrates a role for serologic testing to increase diagnostic sensitivity

Background

Since February 2020, Italian hospitals registered COVID-19 (COronaVIrus Disease 19) cases more often than the rest of the Europe. During this epidemic, health authorities requested swab tests, while seeking new patient paths.

Methods

A dual laboratory approach was evaluated, consisting of patient care reports for viral RNA detection on swabs and rapid serological tests in 516 patients (192 symptomatic or paucisymptomatic and 324 asymptomatic).

Results

We found the molecular positive fraction equal to 12% (23/192) among symptomatic/paucisymptomatic (S/P) and 15.4% (50/324) in asymptomatic (As) sets. Among subsets, we observed serologically positive results, corresponding to 35% (8/23) for S/P and 38% (19/50) for As. Among molecular negative cases, we detected specific Immunoglobulin G or M (Ig G or Ig M) positivity in the S/P cohort equal to 6.6% (11/167) and 6% (15/246) in As cases. For indeterminate molecular results, we found S/P serological positivity equal to 100% (1/1) and 54% (13/24) in As patients. We found higher (p < 0.05) seropositivity in older patients (n = 8) among symptomatic and positives for viral RNA (n.23).

Conclusions

It has been observed that a dual approach of serological and molecular tests detects a higher absolute number of disease cases in a pandemic context,which could improve monitoring and health surveillance efficacy. The age-related seropositivity frequency in this study, if confirmed, could enhance the validity of serological tests, especially in older patients.In these subjects, molecular positivity accompanied by serological positivity (distinct for M and G immunoglobulins) should help determine disease status and support decisions related to patient management.

Diagnostic accuracy of tests using recombinant protein antigens of Mycobacterium leprae for leprosy: A systematic review

The aim of this systematic review was to investigate the studies that evaluated the sensitivity and specificity of serologic tests using recombinant protein antigens from Mycobacterium leprae for leprosy diagnosis. We included 13 studies that were available in PubMed, Brazilian Virtual Library of Health, Web of Science, ScienceDirect and Scopus. From these studies, we found that the recombinant serine-rich 45-kDa protein of M. leprae (ML0411) demonstrated high performance for multibacillary (MB) also to paucibacillary (PB) patients, although this study was tested only for Indian population. Despite that, studies using the ND-O-LID antigen have been able to more accurately identify new cases of leprosy among people living in endemic or non-endemic areas and household contacts in Brazil, Colombia, and the Philippines, especially when combined with other biomarkers. Finally, low sensitivity values for PB patients' antibodies response remain challenging for tests intended to diagnose clinical forms that comprise this classification in leprosy.

Serological evidence of Leishmania infection by employing ELISA and rapid tests in captive felids and canids in Brazil

Visceral leishmaniasis (VL) is a zoonosis and the dog is considered the most important urban reservoir. Cases in cats have been reported, but little is known about Leishmania infection and disease in wild felids and canids kept in captivity in endemic areas. Thus, the serological pattern of wild felids and canids kept in captivity at the Belo Horizonte Zoological Garden was investigated using two primary antigens for conventional ELISA: k39 and rKDDR, as well as three serological rapid kits: Dual Path Platform (DPP®) immunochromatographic test, rKDDR Immunochromatographic assay and ELISA SNAP Leishmania IDEXX®. A total of 21 serum samples, 13 of wild felids and 8 wild canids of varying age and sex were evaluated. The results obtained in the tests were analyzed by agreement using Kappa coefficient, and between ELISA antigens all the analysis performed had showed significant agreement among both of them, as well between the three immunochromatographic tests. The results demonstrated that there is serological evidence of wild animals seropositive for Leishmania antibodies at the Belo Horizonte Zoological Garden, and that all the antigens and rapid tests used can be employed in serological screening for VL in wild felids and canids.

Leishmania infantum exo-antigens: application toward serological diagnosis of visceral leishmaniasis

The laboratory diagnosis of visceral leishmaniasis (VL) presents limitations related to its sensibility and/or specificity. In this context, the aim of this study was to evaluate an enzyme-linked immunoassay to detect IgG antibodies against Leishmania infantum exo-antigens for diagnosis of VL, called ELISA-Exo. This assay was applied in 309 masked serum samples from VL, tegumentary leishmaniasis, Chagas disease, schistosomiasis mansoni, malaria patients, and healthy individuals. The results were compared with those from ELISA using rK39 as antigen (ELISA-rK39). The ELISA assays presented sensitivity of 96.8% and 98.4% (p = 0.68), specificity of 92.4% for both, and diagnostic accuracy of 94.2% and 94.8% (p = 0.48) by the ELISA-Exo and ELISA-rK39, respectively. An excellent agreement beyond chance (Kappa index = 0.82) was obtained when the results from ELISA assays were cross-tabulated. The Western blotting showed that false-positive results presented by ELISA-Exo probably were produced by cross-reactivity of antigens shared with the species of the family Trypanosomatidae. In the future, an immunoproteomic approach can contribute for identification of main immunoreactive L. infantum exo-antigens.

Reasons behind the epidemiological situation of brucellosis in the Republic of Kazakhstan

Brucellosis is endemic in the Republic of Kazakhstan, particularly in agro-pastoral areas. The purpose of this research is to study the epidemiological situation of brucellosis in livestock recorded in the Republic of Kazakhstan, and to identify the reasons why anti-brucellosis measures were not effective. The research was performed on statistical data provided by the Republican Veterinary Laboratory (RVL), the Ministry of Agriculture of the Republic of Kazakhstan. The analysis touched upon the prevalence of Brucellosis in cattle and small ruminants (sheep and goats) in 13 regions of the Republic of Kazakhstan in 2012-2016. Aside from that, Research Institute for Biological Safety Problems conducted screening assays that involved 11,889 samples of blood and tissues from said animals. The risks of developing Brucellosis were assessed for each particular region. The comparison of studies conducted in 2012-2016 reveals an increase in the prevalence of Brucellosis in cattle in the following regions: West Kazakhstan, Karaganda Region and Pavlodar Region. For small ruminants, growing prevalence was observed in the Kostanay Region, Jambyl Region and Almaty Region. Between 2014 and 2016, the incidence rate had a growing trend, with a high in 2014 and 2015. The lowest prevalence rate during the following years (2012-2016) was in the Mangystau Region. The Enzyme-Linked Immunosorbent Assay (ELISE) test applied in the research among other tests provided the best results. The main risk factors involve epidemiology and sanitary measures, which are undertaken in the Republic of Kazakhstan, geography of the region with focuses of infection, and randomness of spread.

Evaluation of serological cross-reactivity between yellow fever and other flaviviruses

OBJECTIVES

This study was performed to determine whether neutralizing antibodies against yellow fever virus (YFV) generated by YFV vaccine could interfere in the specificity of dengue virus (DENV) and Zika virus (ZIKV) IgG ELISA tests.

METHODS

Seventy-nine pairs of serum samples (pre- and post-vaccination), collected during the years 1997-1998 from children with no history of yellow fever disease who had been vaccinated against YFV, were tested. The seroconversion post-vaccination was evaluated through plaque reduction neutralization test (PRNT), and four different commercial ELISA kits were used for the detection of DENV and ZIKV IgG antibodies.

RESULTS

A cross-reactivity rate of 3.9% with DENV IgG antibodies was found only with the Dengue Virus IgG Dx Select kit (Focus Diagnostics).

CONCLUSIONS

As several countries have local transmission of multiple arboviruses, the absence of cross-reactivity or minimum cross-reactivity of YFV neutralizing antibodies with DENV and ZIKV antigens is a relevant finding, since the interpretation of sero-epidemiological investigations would be seriously impacted in many regions where YFV vaccination is mandatory.

Effective chemical virus inactivation of patient serum compatible with accurate serodiagnosis of infections

Objectives

Highly pathogenic viruses such as EBOV are a threat to routine laboratory workers. Inactivation procedures with Triton X-100 0.1% and/or heat are currently recommended, but have unknown effects on the accuracy of serological testing. Furthermore, virus inactivation by Triton X-100 0.1% was shown to be ineffective in serum. This study aimed to demonstrate virus inactivation in serum by Triton X-100 1% and maintained accuracy of serological testing.

Methods

A panel of 19 serological tests was run on patient serum samples after treatment with Triton X-100 1%, 0.1%, and 0.1% + heat inactivation at 60°C for 1 h. Mean differences between measurements (bias) were calculated applying the Bland–Altman method. To determine effectiveness of virus inactivation, herpes simplex virus 1 (HSV-1) was spiked into medium containing 90% or 1% serum, and treated with Triton X-100 0.1% or 1%. Infectious titres were then determined on Vero cells.

Results

Serological measurements showed good agreement between controls and samples treated with Triton X-100 0.1% and 1%, with an estimated bias of 0.6 ± 9.2% (n = 258) and –0.1 ± 18.6% (n = 174), respectively. Discordant qualitative results were rare. Conversely, heat inactivation alone and combined with Triton X-100 0.1% triggered a bias of 17.5 ± 66.4% (n = 200) and 37.9 ± 79.8% (n = 160), respectively. Triton X-100 1% completely inactivated HSV-1 in 1% and 90% serum while Triton X-100 0.1% failed to do so in 90% serum.

Conclusions

Unlike heat inactivation, Triton X-100 1% enabled accurate serological testing and completely inactivated HSV-1 in serum. This simple method could allow safe routine serological diagnostics in high-risk patients.

Comparison of standard agglutination tests, enzyme immunoassay, and Coombs gel test used in laboratory diagnosis of human brucellosis

Background/aim: It was aimed to evaluate the results of Rose Bengal (RB), ELISA total tests (IgM and IgG), and the Brucella Coombs gel test (BCGT), which are used as screening tests, with the combined results of a tube agglutination test (standard Wright test: SWT) and a tube agglutination test with antihuman globulin (AHG TAT). Materials and methods: Samples from 97 patients prediagnosed with brucellosis (age ≥18 years) were screened with RB, ELISA, and BCGT. SWT < 160 samples and RB-negative but ELISA- or BCGT-positive samples were tested by AHG TAT. SWT ≥ 160 or AHG TAT ≥ 160 was taken as reference. Results: Thirty-two of 56 RB-positive samples and one RB-negative but ELISA- and BCGT-positive sample were found to be ≥160 with SWT or AHG TAT. Sensitivity, specificity, accuracy, and agreement (kappa) values according to SWT ≥ 160 or AHG TAT ≥ 160 positivity were as follows, respectively: RB 96.9%, 62.5%, 74.2%, and 0.509; ELISA total 100%, 60.9%, 74.2%, and 0.515; BCGT test 97%, 70.3%, 79.4%, and 0.594. Conclusion: Sensitivities of the screening tests are similar, but positivities should be confirmed by more specific tests. Positive samples from screening tests should be tested with AHG if the SWT value is <160.

Diagnostic aptitude of West Nile virus-like particles expressed in insect cells

West Nile virus is a globally spread zoonotic arbovirus. The laboratory diagnosis of WNV infection relies on virus identification by RT-PCR or on specific antibody detection by serological tests, such as ELISA or virus-neutralization. These methods usually require a preparation of the whole virus as antigen, entailing biosafety issues and therefore requiring BSL-3 facilities. For this reason, recombinant antigenic structures enabling effective antibody recognition comparable to that of the native virions, would be advantageous as diagnostic reagents. WNV virions are enveloped spherical particles made up of 3 structural proteins (C, capsid; M, membrane and E, envelope) enclosing the viral RNA. This study describes the co-expression of these 3 proteins yielding non-infectious virus-like particles (VLPs) and the results of the initial assessment of these VLPs, used instead of the whole virus, that were shown to perform correctly in two different ELISAs for WNV diagnosis.

Maternally-derived antibodies do not inhibit swine influenza virus replication in piglets but decrease excreted virus infectivity and impair post-infectious immune responses

Maternally-derived antibodies (MDA) reduce piglet susceptibility to swine influenza A virus, but interfere with post-infectious immune responses, raising questions about protection after waning of passive immunity. We therefore analysed the impact of different levels of residual MDA on virus excretion and immune responses in piglets born to vaccinated sows (MDA+) and infected with H1N1 at 5, 7 or 11 weeks of age, in comparison to piglets born to unvaccinated sows (MDA-). Subsequent protection against a second homologous infection occurring 4 weeks after the primo-infection was also investigated. MDA- pigs showed clinical signs, shed the virus, and developed specific immune responses despite some age-dependent differences: 7-week-old pigs were less affected clinically, showed a 2-day delayed excretion peak and excreted less virus than younger pigs. In MDA+ animals, clinical signs increased together with the decrease of MDA levels related to the age at infection-time. Virus shedding was not prevented and genome quantification profiles were similar to those obtained in MDA- piglets. However, viral particles excreted by 5-week-old MDA+ piglets appeared to be less infectious than those shed by MDA- piglets at the same age. Humoral response was affected by MDA as illustrated by the absence of HI and neutralizing response regardless the infection age, but anti-NP/M responses were less affected. Proliferative T cell responses were slightly delayed by high MDA levels. Nevertheless, MDA+ animals were all protected from a second infection, like MDA- piglets. In conclusion, responses of pigs to H1N1 were affected by both the physiological development of animals at infection and the MDA level.

Infection by Streptococcus pneumoniae in children with or without radiologically confirmed pneumonia

OBJECTIVE

Community-acquired pneumonia is an important cause of morbidity in childhood, but the detection of its causative agent remains a diagnostic challenge. The authors aimed to evaluate the role of the chest radiograph to identify cases of community-aquired pneumonia caused by typical bacteria.

METHODS

The frequency of infection by Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis was compared in non-hospitalized children with clinical diagnosis of community acquired pneumonia aged 2-59 months with or without radiological confirmation (n=249 and 366, respectively). Infection by S. pneumoniae was diagnosed by the detection of a serological response against at least one of eight pneumococcal proteins (defined as an increase ≥2-fold in the IgG levels against Ply, CbpA, PspA1 and PspA2, PhtD, StkP-C, and PcsB-N, or an increase ≥1.5-fold against PcpA). Infection by H. influenzae and M. catarrhalis was defined as an increase ≥2-fold on the levels of microbe-specific IgG.

RESULTS

Children with radiologically confirmed pneumonia had higher rates of infection by S. pneumoniae. The presence of pneumococcal infection increased the odds of having radiologically confirmed pneumonia by 2.8 times (95% CI: 1.8-4.3). The negative predictive value of the normal chest radiograph for infection by S. pneumoniae was 86.3% (95% CI: 82.4-89.7%). There was no difference on the rates of infection by H. influenzae and M. catarrhalis between children with community-acquired pneumonia with and without radiological confirmation.

CONCLUSIONS

Among children with clinical diagnosis of community-acquired pneumonia submitted to chest radiograph, those with radiologically confirmed pneumonia present a higher rate of infection by S. pneumoniae when compared with those with a normal chest radiograph.

Reliable Serological Testing for the Diagnosis of Emerging Infectious Diseases

Climate change, increased urbanization and international travel have facilitated the spread of mosquito vectors and the viral species they carry. Zika virus (ZIKV) is currently spreading in the Americas, while dengue virus (DENV) and chikungunya virus (CHIKV) have already become firmly established in most tropical and also many non-tropical regions. ZIKV, DENV and CHIKV overlap in their endemic areas and cause similar clinical symptoms, especially in the initial stages of infection. Infections with each of these viruses can lead to severe complications, and co-infections have been reported. Therefore, laboratory analyses play an important role in differential diagnostics. A timely and accurate diagnosis is crucial for patient management, prevention of unnecessary therapies, rapid adoption of vector control measures, and collection of epidemiological data.There are two pillars to diagnosis: direct pathogen detection and the determination of specific antibodies. Serological tests provide a longer diagnostic window than direct methods, and are suitable for diagnosing acute and past infections, for disease surveillance and for vaccination monitoring. ELISA and indirect immunofluorescence test (IIFT) systems based on optimized antigens enable sensitive and specific detection of antibodies against ZIKV, DENV and CHIKV in patient serum or plasma. In recent years, Euroimmun (Lübeck, Germany) has developed numerous test systems for the serological diagnosis of (re-)emerging diseases, including a very sensitive and specific anti-ZIKV ELISA.

Serological tests for gambiense human African trypanosomiasis detect antibodies in cattle

Background

Serological tests for gambiense human African trypanosomiasis (gHAT) detect antibodies to antigens on the cell surface of bloodstream trypanosomes. As trypanosomes that cause animal African trypanosomiasis (AAT) also express related antigens, we have evaluated two rapid diagnostic tests (RDTs) on cattle in trypanosomiasis endemic and non-endemic regions, to determine whether gHAT serological tests could also be used to screen for AAT.

Methods

Two RDTs, 1G RDT, made with native antigens, and p2G RDT, made with recombinant antigens, were tested on 121 cattle in a trypanosomiasis-free region, and on 312 cattle from a rhodesiense HAT and AAT endemic region. A subset of samples from the endemic region were also tested with two immune trypanolysis (TL) tests. The sensitivity of the tests was estimated by evaluating the result of the RDT on samples that were positive by both microscopy and internal transcribed spacer (ITS) PCR, whilst specificity was the result of the RDT on samples that were negative by ITS PCR and microscopy, and others from the non-endemic region.

Results

The specificity of the p2G RDT on cattle from the non-endemic region was 97.5% (95% CI: 93.0–99.2%), compared to only 57.9% (95% CI: 48.9–66.3%) for 1G RDT. The specificities of 1G RDT, p2G RDT and TL on endemic control cattle were 14.6% (95% CI: 9.7–21.5%), 22.6% (95% CI: 16.4–30.3%) and 68.3% (95% CI: 59.6–75.9%), respectively. The sensitivities of the tests on trypanosome positive samples were 85.1% (95% CI: 79.1–89.7%), 89.1% (95% CI: 83.7–93.0%) and 59.3% (95% CI: 51.8–66.4%), respectively. Among the same samples, 51.7% were positive by both TL and the 1G RDT.

Conclusions

These serological tests detect cross-reacting antibodies in cattle. The p2G RDT based on recombinant antigens had a high specificity in a non-endemic region, while the 1G RDT had a lower specificity, suggesting cross-reactivity with other pathogens.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2487-8) contains supplementary material, which is available to authorized users.

Distribution of serological screening markers at a large hematology and hemotherapy center in Minas Gerais, Southeastern Brazil

Objective

To assess the distribution of serological markers in blood donors at the blood banks of the Fundação Centro de Hematologia e Hemoterapia de Minas Gerais (Hemominas), Brazil, between January 2006 and December 2012.

Methods

This is a descriptive, retrospective study on blood donors screened using serological tests for markers of transmitted diseases at the state blood-banking network.

Results

Approximately 78.9% of the donors were considered eligible for the study after clinical screening. Repeat donors represented 68.2% of the total sample, with males being predominant as blood donors (66.8%). Total serological ineligibility was 3.05%, with total anti-HBc being the most common marker (1.26%), followed by syphilis (0.88%) and human immunodeficiency virus (0.36%). The prevalences of the markers for hepatitis C, Human T-cell lymphotropic virus, Chagas disease and HBs-Ag were 0.15%, 0.09%, 0.13% and 0.18%, respectively. The blood bank of Governador Valadares had the highest percentage of positive anti-HBc donors (2.41%). With regard to human immunodeficiency virus, the blood bank of Além Paraíba had the lowest percentage of positive donors while the blood banks of Juiz de Fora and Betim had the highest percentages. The blood bank in the city of Montes Claros had the highest prevalence of the marker for Chagas disease (0.69%).

Conclusions

Data on the profile of serological ineligibility by the blood banks of the Fundação Hemominas highlights the particularities of each region thereby contributing to measures for health surveillance and helping the blood donation network in its donor selection procedures aimed at improving blood transfusion safety.

Update on hepatitis B and C virus diagnosis

Viral hepatitis B and C virus (HBV and HCV) are responsible for the most of chronic liver disease worldwide and are transmitted by parenteral route, sexual and vertical transmission. One important measure to reduce the burden of these infections is the diagnosis of acute and chronic cases of HBV and HCV. In order to provide an effective diagnosis and monitoring of antiviral treatment, it is important to choose sensitive, rapid, inexpensive, and robust analytical methods. Primary diagnosis of HBV and HCV infection is made by using serological tests for detecting antigens and antibodies against these viruses. In order to confirm primary diagnosis, to quantify viral load, to determine genotypes and resistance mutants for antiviral treatment, qualitative and quantitative molecular tests are used. In this manuscript, we review the current serological and molecular methods for the diagnosis of hepatitis B and C.

Evaluation of the immunochromatographic (Leptocheck) test for detection of specific antibodies against leptospires

BACKGROUND

Leptospirosis is a febrile worldwide zoonosis. Routine diagnosis of leptospiral infection is based on demonstration of specific antibodies with serological tests. Performance of the reference serological test, the microscopic agglutination test (MAT), requires significant expertise. The aim of our study was to find out if leptospiral infection can be proven with simple, rapid, commercially available immunochromatographic Leptocheck test in order to introduce it for the first level diagnosis in emergency cases with less specialized laboratory staff.

METHODS

In all, 590 serum samples of patients with clinical manifestations suggestive of leptospirosis were collected and tested with MAT and Leptocheck test. For confirmation of the results some other diagnostic methods such as polymerase chain reaction (PCR) and Leptospira isolation were performed.

RESULTS

Results of both serological tests were consistent in 576/590 (97.63%) cases but Leptocheck gave more positive results in comparison to MAT (36 and 12, respectively) at first patient's testing. Following up the patient, MAT became positive in majority of Leptocheck positive patients at first visit. Leptospiral DNA was detected in nine blood and six urine samples belonging to thirteen different patients while only two samples were culture positive.

CONCLUSION

In comparison with serological tests, PCR and culture have low sensitivity. According to our findings we conclude that Leptocheck test can prove leptospiral infection and could be used for rapid diagnosis of leptospirosis, later the sample should be confirmed with MAT.

Efficient duplex solid-phase fluorescent assay (dFISA) for the simultaneous detection of specific anti-T. gondii IgG and IgM due to refined conjugates

Toxoplasma gondii infections are very common, causing occasional central nervous system and eye diseases, and must be screened in prenatal care for efficient therapy. Here, we developed a duplex solid-phase fluorescent assay (dFISA) for the simultaneous detection of anti-T. gondii IgG and IgM antibodies in prenatal care screening for toxoplasmosis. Assays using commercially available ion-exchange purified conjugates yielded poor results and high background fluorescence. Same-well IgG/IgM dFISA with refined conjugates was used to test 140 samples from university students, 120 samples from pregnant women and 24 samples from adult volunteers at a large public hospital. We found that dFISA offers high concordance, specificity and reproducibility for IgG (Kappa=0.883) and IgM (Kappa=0.918), which is useful in high-throughput applications for antenatal care.

Presence and duration of anti-Toxoplasma gondii immunoglobulin M in infants with congenital toxoplasmosis

OBJECTIVES

to investigate the rate of positivity for immunoglobulin M anti-Toxoplasma gondii (Toxo-IgM) in newborns with congenital toxoplasmosis, and the age when these antibodies become negative.

METHODS

patients with congenital toxoplasmosis who started monitoring in a congenital infection clinic between 1998 and 2009 were included. Inclusion criteria were routine maternal or neonatal serological screening; diagnostic confirmation by persistence of immunoglobulin G anti-Toxoplasma gondii at age ≥ 12 months, and Toxo-IgM screening in the neonatal period. To calculate the frequency of positive Toxo-IgM, cases detected by neonatal screening were excluded. For the study of the age when Toxo-IgM results became negative, patients with negative Toxo-IgM since birth and those in whom it was not possible to identify the month when the negative result was achieved were excluded.

RESULTS

among the 28 patients identified through maternal screening, 23 newborns had positive Toxo-IgM (82.1%, 95% CI: 64.7-93.1%). When adding the 37 patients identified by neonatal screening, Toxo-IgM was positive in the first month of life in 60 patients, and it was possible to identify when the result became negative in 51 of them. In 19.6% of patients, these antibodies were already negative at 30 days of life; and in 54.9%, at 90 days. Among the 65 patients included in the study, 40 (61.5%) had some clinical alteration.

CONCLUSIONS

even with high sensitivity methods, newborns with congenital toxoplasmosis can have negative Toxo-IgM at birth. In those who have these antibodies, the positive period may be quite short. It is important not to interrupt the monitoring of infants with suspected congenital toxoplasmosis simply because they present a negative Toxo-IgM result.

A bacterial engineered glycoprotein as a novel antigen for diagnosis of bovine brucellosis

Brucellosis is a highly contagious zoonosis that affects livestock and human beings. Laboratory diagnosis of bovine brucellosis mainly relies on serological diagnosis using serum and/or milk samples. Although there are several serological tests with different diagnostic performance and capacity to differentiate vaccinated from infected animals, there is still no standardized reference antigen for the disease. Here we validate the first recombinant glycoprotein antigen, an N-formylperosamine O-polysaccharide-protein conjugate (OAg-AcrA), for diagnosis of bovine brucellosis. This antigen can be produced in homogeneous batches without the need of culturing pathogenic brucellae; all characteristics that make it appropriate for standardization. An indirect immunoassay based on the detection of anti O-polysaccharide IgG antibodies in bovine samples was developed coupling OAg-AcrA to magnetic beads or ELISA plates. As a proof of concept and to validate the antigen, we analyzed serum, whole blood and milk samples obtained from non-infected, experimentally infected and vaccinated animals included in a vaccination/infection trial performed in our laboratory as well as more than 1000 serum and milk samples obtained from naturally infected and S19-vaccinated animals from Argentina. Our results demonstrate that OAg-AcrA-based assays are highly accurate for diagnosis of bovine brucellosis, even in vaccinated herds, using different types of samples and in different platforms. We propose this novel recombinant glycoprotein as an antigen suitable for the development of new standard immunological tests for screening and confirmatory diagnosis of bovine brucellosis in regions or countries with brucellosis-control programs.

Why are inaccurate tuberculosis serological tests widely used in the Indian private healthcare sector? A root-cause analysis

Serological tests for tuberculosis are inaccurate and WHO has recommended against their use. Although not used by the Revised National TB Control Programme (RNTCP), serodiagnostics are widely used in the private sector in India. A root-cause analysis was undertaken to determine why serological tests are so popular, and seven root causes were identified that can be grouped into three categories: technical/medical, economic, and regulatory. Technical/medical: RNTCP's current low budget does not allow scale-up of the newer, WHO-endorsed technologies. Thus, under the RNTCP, most patients have access to only smear microscopy, a test that is insensitive and underused in the private sector. Because there is no accurate, validated, point-of-care test for TB, serological tests meet a perceived need among doctors and patients. Economic: While imported molecular or liquid culture tests are too expensive, there are no affordable Indian versions on the market, leaving serological tests as the main alternative. Although serological tests are inaccurate, various players along the value chain profit from their use, and this sustains a market for these tests. Regulatory: TB tests are poorly regulated and a large number of serological kits are on the market. Private healthcare in general is poorly regulated, and doctors in the private sector are outside the scope of RNTCP and do not necessarily follow standard guidelines. A clear understanding of these realities should facilitate market-based strategies that can help replace serological tests with accurate, validated tools.