Performance Of Serological Tests Research Articles

Differences of SARS-CoV-2 serological test performance between hospitalized and outpatient COVID-19 cases

BackgroundSerological severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody assays differ in the target antigen specificity, e.g. of antibodies directed against the viral spike or the nucleocapsid protein, and in the spectrum of detected immunoglobulins. The aim of the study was to evaluate the performance of two different routinely used immunoassays in hospitalized and outpatient COVID-19 cases. MethodsThe test characteristics of commercially available spike1 protein-based serological assays (Euroimmun, EI-assays), determining IgA or IgG and nucleocapsid-based assays (Virotech, VT-assays) determining IgA, IgM or IgG were compared in 139 controls and 116 hospitalized and outpatient COVID-19 cases. ResultsHospitalized COVID-19 patients (n = 51; 115 samples) showed significantly higher concentrations of antibodies against SARS-CoV-2 and differed from outpatient cases (n = 65) by higher age, higher disease severity scores and earlier follow up blood sampling. Sensitivity of the two IgG assays was comparable in hospitalized patients tested ≥ 14 days (EI-assay: 88%, CI95% 67.6–99.9; VT-assay: 96%, CI95% 77.7–99.8). In outpatient COVID-19 cases sensitivity was significantly lower in the VT-assay (86.2%, CI95% 74.8–93.1) compared with the EI-assay (98.5%, CI95% 90.6–99.9). Assays for IgA and IgM demonstrated a lack of specificity or sensitivity. ConclusionsOur results indicate that SARS-CoV-2 serological assays may need to be optimized to produce reliable results in outpatient COVID-19 cases who are low or even asymptomatic. Assays for IgA and IgM have limited diagnostic performance and do not prove an additional value for population-based screening approaches.

Serology Curriculum for Residents Using Online, Case-Based Simulation Modules

Abstract Background Although serology concepts are a frequent topic of examination for Pathology trainees, serology education is challenging, in part, because the performance of serologic tests may occur in different laboratories (immunology, microbiology, or chemistry.) Serology educational topics and curriculums may be eclipsed by topics concerning the larger laboratory in which serology resides. We developed a one-week standalone curriculum in which residents were given four case-based vignettes to solve and discuss with a faculty member, eight online case-based simulation modules, and bench time in the laboratory with medical laboratory scientists performing serological tests (RPR, VDRL, hepatitis, and HIV). Objectives To evaluate the advantages and educational utility of online modules as adjuncts to other modalities used during a standalone serology rotation. Methods The online modules are housed within an e-learning Portal. Residents were asked to print the certificate of completion for the eight modules assigned at the end of the week. A survey of the week-long rotation was given to the residents one week and up to 2 months after the rotation. Residents could complete the survey anonymously. Results Twenty-three first-year residents (representing a 3-year period) presented completion certificates for the online modules, but only 10 (43.5%) responded to the survey. The average percentage of correct answers for online modules ranged from 73% for the HIV module to 88% for the hepatitis B module. The number of residents with scores below 80% was highest for the Epstein-Barr virus (EBV) and Cryptococcus modules (8 and 9 residents scoring <80% respectively) and lowest for hepatitis B and toxoplasmosis modules (2 and 3 respectively). On the survey, residents stated that they had repeated the online modules between 1 and 4 times, with an average of 1 to 2 attempts. Although there was not a specific module rated as the most enjoyable, the toxoplasmosis and EBV modules were picked by 3 out of 10 residents as his or her favorite. There was no consensus on which module was subjectively easiest or most difficult, nor which was the least enjoyed. The majority of the residents (7/10) found the online modules helpful and all ten residents stated that they learned more after completion of the online modules as the modules reinforced (6/10) concepts important to serologic testing. Conclusions The online, case-based simulation modules are an effective addition to a serology curriculum that includes case-based discussions and time spent in the laboratory participating in test performance. The online modules are an effective educational tool because they reinforce learning and provide additional structure to the serology curriculum.

Performance of Mumps PCR and Serologic Testing During a University-Associated Mumps Outbreak in Charleston, SC

Background: Sensitive diagnostic testing is critical in responses to mumps outbreaks. PCR testing of buccal swabs is the most sensitive diagnostic test, but IgM serology remains standard in much of the United States. We provided testing guidance stressing use of mumps PCR to ambulatory clinics and emergency departments in addition to the standard serologic testing for acute mumps beginning in 2018. We compared the performance of PCR and IgM serology to assess cases of parotitis presenting during a community outbreak of mumps in fall 2019 associated with a university in Charleston, SC. Methods: All patients tested for mumps who presented to our facility (ER and ambulatory clinics) with mumps PCR and/or mumps IgM ordered between September 2019 and January 2020 were included. Mumps PCRs were sent to a commercial reference laboratory (ARUP). Confirmed cases were defined as having a positive mumps PCR and/or IgM with parotitis. Clinical characteristics of mumps patients including age, duration of symptoms, MMR history, and association with the university were obtained by chart review. Results: Mumps was confirmed in 15 of 44 tested patients (34%), with 15 of 15 mumps patients (100%) having positive PCR and 1 of 15 patients (7%) and 1 of 15 patients (7%) having positive and equivocal mumps IgM serologies, respectively. Only 1 patient who did not meet our mumps case definition (no CT imaging evidence of parotitis, no fevers, chronic sinus symptoms) had a positive PCR and had recent receipt of a third MMR dose in response to the ongoing outbreak. Median age for mumps patients was 22 years (range, 15–48) with 8 of 15 cases (53%) detected among university students and an additional 2 cases having close connections to the university associated with the outbreak. Only 1 of 15 mumps patients (6.7%) was febrile at presentation (median temperature, 37.2°C) and mumps cases presented for testing ≤3 days for 7 of 15 cases (47%) (range, 0–13 days from symptom onset). No cases were diagnosed by IgM only, and 10 of 15 mumps cases had some recollection of remote MMR immunization, whereas 6 of 15 (40%) had 2 documented MMR doses at <5 years of age. Conclusion: Serologic IgM testing for diagnosis of mumps appears insensitive for detection of cases in outbreaks within highly immunized adult patients. Although our recommended shift to PCR likely enhanced case finding during this outbreak, the potential for false-positive PCRs due to vaccine strain shedding following third-dose MMR immunization may also be considered a threat to the specificity of the test during outbreak situations.Funding: NoneDisclosures: None

Liver fibrosis with two-dimensional shear-wave elastography in patients with autoimmune hepatitis

ABSTRACT Background Two-dimensional shear-wave elastography (2D-SWE) is an ultrasound-based real-time 2D-SWE imaging technique for noninvasive assessment of liver fibrosis. The diagnostic performance of 2D-SWE for assessing liver fibrosis in patients with autoimmune hepatitis (AIH) has not been reported. Aims To evaluate the diagnostic performance of 2D-SWE and serologic tests including the aspartate amino transferase-to-platelet ratio index (APRI) and fibrosis-4 index (FIB-4) for liver fibrosis staging in patients with AIH. Methods 103 patients were retrospectively collected. Liver fibrosis was staged according to the Scheuer scoring system. The areas under the receiver operating characteristic curves (AUROCs) were used to assess the accuracy of 2D-SWE and serum fibrosis models for staging liver fibrosis. Results Liver stiffness measured by 2D-SWE had a strong correlation with histological fibrosis stage (r = 0.71, P < 0.0001). The AUROCs of liver stiffness in detecting significant fibrosis, severe fibrosis, and cirrhosis were 0.84, 0.84, and 0.94, respectively. The AUROCs of liver stiffness for detecting significant fibrosis and severe fibrosis were higher than those of APRI (0.57, 0.56) and FIB-4 (0.63, 0.66), respectively. The cut‐off liver stiffness values for predicting significant fibrosis, severe fibrosis, and cirrhosis were 10.0, 15.8, and 19.3 kPa, respectively. Conclusions 2D-SWE shows promising diagnostic performance for staging liver fibrosis in patients with AIH.

Seroepidemiologic Study Designs for Determining SARS-COV-2 Transmission and Immunity.

Serologic studies are crucial for clarifying dynamics of the coronavirus disease pandemic. Past work on serologic studies (e.g., during influenza pandemics) has made relevant contributions, but specific conditions of the current situation require adaptation. Although detection of antibodies to measure exposure, immunity, or both seems straightforward conceptually, numerous challenges exist in terms of sample collection, what the presence of antibodies actually means, and appropriate analysis and interpretation to account for test accuracy and sampling biases. Successful deployment of serologic studies depends on type and performance of serologic tests, population studied, use of adequate study designs, and appropriate analysis and interpretation of data. We highlight key questions that serologic studies can help answer at different times, review strengths and limitations of different assay types and study designs, and discuss methods for rapid sharing and analysis of serologic data to determine global transmission of severe acute respiratory syndrome coronavirus 2.

Meta-analysis of diagnostic performance of serological tests for SARS-CoV-2 antibodies up to 25 April 2020 and public health implications.

We reviewed the diagnostic accuracy of SARS-CoV-2 serological tests. Random-effects models yielded a summary sensitivity of 82% for IgM, and 85% for IgG and total antibodies. For specificity, the pooled estimate were 98% for IgM and 99% for IgG and total antibodies. In populations with ≤ 5% of seroconverted individuals, unless the assays have perfect (i.e. 100%) specificity, the positive predictive value would be ≤ 88%. Serological tests should be used for prevalence surveys only in hard-hit areas.

Validation of a chemiluminescent assay for specific SARS-CoV-2 antibody.

Objectives Faced with the COVID-19 pandemic and its impact on the availability and quality of both therapeutic and diagnostic methods, the Belgian authorities have decided to launch a procedure for additional evaluation of the performance of serological tests offered for sale on the national territory. This has been proposed with a double aim: (1) an in-depth verification of the analytical and clinical performances presented by the manufacturer and (2) an economy of scale in terms of centralized validation for all the laboratories using the tests subject to evaluation. Methods A retrospective validation study was conducted including the serum of 125 patients in order to determine the analytical and clinical performances of the LIAISON®SARS-CoV-2 from DiaSorin® detecting anti-SARS-CoV-2 IgG and to compare its clinical performance with the enzyme-linked immunosorbent assay (ELISA) test from Euroimmun®, one of the first commercially available tests allowing the detection of anti-SARS-CoV-2 IgA and IgG. Results The performances of the LIAISON®SARS-CoV-2 satisfied all the acceptance criteria and provided "real world" analytical and clinical performances very close to the ones reported by the manufacturer in its insert kit. Comparison between the LIAISON®SARS-CoV-2 and the ELISA method did not reveal any difference between the two techniques in terms of sensitivities and specificities regarding the determination of the IgG. Conclusions This study reports the validation of the LIAISON®SARS-CoV-2 allowing to detect IgG antibodies specifically directed against SARS-CoV-2. The analytical and clinical performances are excellent, and the automation of the test offers important rates, ideal for absorbing an extension of testing.

Consenso de grupo Ad-hoc sobre recomendaciones para la evaluación y controles de calidad para el diagnóstico molecular y serológico de la infección humana por SARS CoV-2

Se formulan recomendaciones de un grupo de consenso de expertos sobre los criterios para evaluar el desempeño diagnóstico (tamaño y selección de muestras para sensibilidad y especificidad analíticas, criterios para establecer límites de detección, criterios para establecer el estándar de oro para las serologías) que deberían ser tenidos en cuenta al evaluar y validar las pruebas diagnósticas para SARS CoV-2. Con el propósito de asegurar la calidad de las pruebas serológicas a utilizar en el país, se recomienda la participación en un programa de control de calidad externo, que garantice la idoneidad y desempeño en la realización de las pruebas diagnósticas serológicas y moleculares durante esta pandemia, ya que su uso tiene profundas implicaciones para las medidas de intervención clínicas individuales y de seguimiento y control en salud pública.

Laboratorial algorithm for serological diagnosis of visceral leishmaniasis using rK39-ICT, DAT-LPC and FC-Simplex IgG1

The performance of distinct serological tests (rK39-ICT, IFAT, DAT-LPC, FC-Simplex IgG1) was assessed and a laboratorial algorithm was proposed for accurate diagnosis of VL. DAT-LPC and FC-Simplex IgG1 showed outstanding accuracy (AUC = 0.93) to identify VL patients. The use of a sequential serological algorithm (rK39-ICT screening followed by DAT-LPC or FC-Simplex IgG1) improved the global accuracy for VL (97.2%) diagnosis. An alternative approach for diagnosis of VL has been also assessed for interchangeable use of serum/whole blood lysate samples in DAT-LPC and FC-Simplex IgG1. Our data showed an outstanding agreement for the results obtained with whole blood lysate samples as compared to serum samples (DAT-LPC =100%; FC-Simplex IgG1 = 99%). Together, these findings provide insights to improve the current overall accuracy of VL diagnosis and present innovative laboratorial tests and alternative samples from use in public health services.

1655. Performance of Molecular and Serologic Tests for the Diagnosis of Scrub Typhus

BackgroundDiagnosis of scrub typhus, caused by the bacterium Orientia tsutsugamushi, is challenging because of the overlap of its nonspecific symptoms with other infections coupled with the lack of sufficient data on the performance of diagnostic tests. Early diagnosis of scrub typhus is crucial to improve outcomes and this study evaluated the diagnostic performance of various tests.MethodsAdult patients with acute febrile illness and manifestations suggestive of scrub typhus confirmed by positive PCR in the blood or eschar were characterized as cases. Patients with acute febrile illness and a confirmed alternate etiology such as culture-confirmed typhoid, smear/PCR positive for malaria, PCR/NS1 antigen positive for dengue, PCR positive for influenza, PCR/MAT positive for leptospirosis, PCR positive for spotted fever were characterized as controls with other infections. The healthy controls consisted of subjects from the same geographic region. We performed the following tests on blood samples for scrub typhus and calculated the sensitivity, specificity, positive predictive value, and negative predictive value: (1) Quantitative PCR using 47 kDa gene (qPCR); (2) Conventional PCR using 56kDa gene (cPCR); (3) Loop-mediated isothermal amplification assay (LAMP assay); (4) Immunofluorescence assay (IFA); (5) Enzyme-linked immunosorbent assay (ELISA); (6) Weil–Felix test (WF test); and (7) Immunochromatographic Rapid Diagnostic Test (RDT).ResultsAmong the 302 participants, 152 had confirmed scrub typhus (cases) and 150 were controls. ELISA and RDT detecting IgM antibodies had excellent discriminative potential with sensitivities and specificities of 94%, 93% and 92%, 93%, respectively. False-positive IgM serology was observed with spotted fever and leptospirosis. The sensitivity and specificity of IFA were found to be 80% and 85%, respectively. qPCR exhibited excellent sensitivity (96%) and perfect specificity.ConclusionELISA and RDT detecting IgM antibodies have excellent sensitivity and specificity while the sensitivity of IFA is suboptimal for the diagnosis of scrub typhus. Given its perfect specificity and superior sensitivity, qPCR is preferred for diagnostic confirmation in reference laboratories.Disclosures All authors: No reported disclosures.

Accuracy of PCR and serological testing for the diagnosis of primary syphilis: Both tests are necessary.

Syphilis, caused by the spirochete Treponema pallidum subspecies pallidum, is a rising global public health concern and laboratory diagnostics remain challenging. Especially during early disease, rapid and accurate diagnosis is crucial to ensure patients and their contacts receive timely treatment to eradicate infection and prevent further transmission. In this prospective observational study, we evaluated the performance of polymerase chain reaction (PCR) and serological testing for the diagnosis of primary syphilis by evaluating anogenital swabs and sera from 178 Cuban patients presenting with ulcers. Three different PCR assays were evaluated targeting polA, tpp47 and 16S rDNA loci. Sera were evaluated with venereal disease research laboratory (VDRL) and T. pallidum hemagglutination (TPHA) assays. Assuming both methods were confirmatory, our data showed that PCR and serology did not correlate well (agreement = 52.3%, kappa 0.0512, 95% CI −0.0928–0.1951, p = 0.496). The sensitivities, specificities, positive and negative predictive values of the PCR assays were 76.1%, 100%, 100% and 57.9%, respectively, while the values for serology were 62.5%, 100%, 100% and 45.2%, respectively. The combination of PCR and serology can offer valuable information for the diagnosis of syphilis in patients presenting with anogenital ulceration avoiding further clinical complications and disease transmission.

Performance of different serological tests in the diagnosis of natural infection by Leishmania infantum in dogs

Visceral leishmaniasis (VL) is a zoonosis caused by the parasite Leishmania infantum and the dog is its main reservoir in rural and urban areas. The diagnosis of infection is mainly based on the presence of anti-Leishmania IgG antibodies in the serum of infected dogs. In this study, the sensitivity and specificity of qualitative rapid tests (RTs) dual path platform (DPP) Bio-Manguinhos, rapid enzyme-linked immunosorbent assay (ELISA) IDEXX, Kalazar Detect and ALERE, as well as quantitative ELISA Bio-Manguinhos and in-house indirect immunofluorescence assay (IFA) tests were analyzed in sera from infected and uninfected dogs. Serial dilutions of the in-house IFA were compared with RTs and ELISA Bio-Manguinhos. The results showed that none of the tests reached 100% sensitivity and specificity. There was no statistical difference between the analyzed RTs. The most sensitive test was the DPP Bio-Manguinhos (97.9%), while the rapid ELISA IDEXX showed higher specificity (100%). In the treatment setting of infected and/or diseased animals, quantitative tests for monitoring the evolution of antibody titers are required, which indicates the maintenance of in-house IFA in animal handling. Furthermore, we demonstrate that the RTs present higher sensitivity in serum samples with superior antibody titers obtained in the in-house IFA. However, the RTs exhibited false negatives in samples with low titers of antibodies. Among the RTs, only the DPP Bio-Manguinhos presented better performance in this situation. Therefore, the use of RTs for the diagnosis of VL in dogs with low titers of antibodies, such as asymptomatic, should be carefully evaluated.

Serologic assessments in acute transfusion reactions: practices and yields

Serologic testing after transfusion reactions (TRs) aims to find accountable immune haemolytic incompatibility. Our hospital policies recommend serologic testing in all TR, except for low-risk fevers (subclinical temperature <39°C) or uncomplicated allergic reactions. Assessing compliance with these guidelines and serologic testing yields may provide insights on quality of practice and value. Interrogation of two haemovigilance databases identified all possible-to-definite TR over a 4-year period (2013-2016) at four academic hospitals. We reviewed the performance and outcome of serologic testing by site, year, reaction type, implicated product and service. Serologic testing occurred in 769 (55%) of 1408 referrals, with 1153 (82%) compliant with guidelines. Similar proportions deviated to overtesting (85/550 [15%]) and undertesting (174/858 [20%]), with undertesting seen most often in atypical TR. Overall, 30 (4.4%) of 769 cases had a new finding, but only 2 (0.3%) reflected host-derived antibodies. Overall, the number needed to test to discover an unexpected allospecificity was 385, or 253 if limited to high-risk fevers. Reaction- and product-specific yields ranged from 0% to 48%. The yield in complicated allergic reactions was low at 2%, constituting only predictable passive isohaemagglutinin(s) in retrospect. Investigated IVIG TR accounted for most of this cohort's signal by passive isohaemagglutinins in 48%. The performance of post-TR serologic testing revealed practice gaps and expected context-specific yields. Tailored serologic testing (i.e. indirect antiglobulin tests for alloantibodies in post-RBC/high-risk febrile reactions, ± isoagglutinin-focused tests after IVIG or ABO-minor-mismatched platelets) may improve value and liberate resources for other unmet needs in TR investigation.

What is the real number of Lyme disease cases in Canada?

BackgroundLyme disease is emerging in Canada due to expansion of the range of the tick vector Ixodes scapularis from the United States. National surveillance for human Lyme disease cases began in Canada in 2009. Reported numbers of cases increased from 144 cases in 2009 to 2025 in 2017. It has been claimed that few (< 10%) Lyme disease cases are reported associated with i) supposed under-diagnosis resulting from perceived inadequacies of serological testing for Lyme disease, ii) expectation that incidence in Canadian provinces and neighbouring US states should be similar, and iii) analysis of serological responses of dogs to the agent of Lyme disease, Borrelia burgdorferi.We argue that performance of serological testing for Lyme disease is well studied, and variations in test performance at different disease stages are accounted for in clinical diagnosis of Lyme disease, and in surveillance case definitions. Extensive surveillance for tick vectors has taken place in Canada providing a clear picture of the emergence of risk in the Canadian environment. This surveillance shows that the geographic scope of I. scapularis populations and Lyme disease risk is limited but increasing in Canada. The reported incidence of Lyme disease in Canada is consistent with this pattern of environmental risk, and the differences in Lyme disease incidence between US states and neighbouring Canadian provinces are consistent with geographic differences in environmental risk. Data on serological responses in dogs from Canada and the US are consistent with known differences in environmental risk, and in numbers of reported Lyme disease cases, between the US and Canada.ConclusionThe high level of consistency in data from human case and tick surveillance, and data on serological responses in dogs, suggests that a high degree of under-reporting in Canada is unlikely. We speculate that approximately one third of cases are reported in regions of emergence of Lyme disease, although prospective studies are needed to fully quantify under-reporting. In the meantime, surveillance continues to identify and track the ongoing emergence of Lyme disease, and the risk to the public, in Canada.

Diagnostic and follow-up performance of serological tests for different forms/courses of alveolar echinococcosis

Diagnosis of alveolar echinococcosis (AE) is predominantly based on imaging procedures combined with immunodiagnostic testing. In the present study, we retrospectively analyzed the performance of four serological tests (EgHF-ELISA, Em2-ELISA, recEm18-ELISA and Em-Immunoblotting) for initial diagnosis and subsequent monitoring of AE patients. Overall, 101 AE patients were included, grouped according to treatment options and immune status as follows: (A) curative surgical treatment (n = 45 patients), (B) non-radical or palliative surgical treatment (n = 11), (C) benzimidazoles only (n = 20), (D) immunocompromised with radical surgical treatment (n = 11), (E) immunocompromised with benzimidazoles only (n = 4), and finally a group of 10 AE patients (F) that were considered to present so-called “abortive” lesions. Initial (i.e. pretreatment) ELISA-based diagnosis for patients in groups A to E revealed overall diagnostic sensitivities of 95% for EgHF, 86% for Em2, and 80% for recEm18, respectively. Comparatively, the diagnostic sensitivity of Em-Immunoblotting was higher with an overall value of 98%. In group F, only Em-Immunoblotting had an excellent diagnostic sensitivity (100%), whereas the ELISAs had poor sensitivities of 30% (EgHF- and Em2-ELISA) or even 0% (recEm18-ELISA).Serological monitoring of AE patients showed a clear association between a curative development of disease (induced either by surgery or benzimidazole medication) and a negativization in the ELISAs. This effect was most pronounced for the recEm18-ELISA, where 56% negativized following diagnosis/treatment, as compared to 36% for the EgHF-ELISA, and 37% for the Em2-ELISA, respectively. After radical surgery, the mean time until negativization in the recEm18-ELISA was 2.4 years (SD 1.6). This was significantly shorter than the mean 3.9 years (SD 2.5) in those AE patients with non-radical, palliative surgery or ABZ treatment who were able to negativize during the study period (p = 0.048).Conclusively, Em-Immunoblotting appears as the most sensitive test to diagnose active as well as inactive (“abortive”) AE-cases. The inclusion of the ELISAs completes the initial diagnostic picture and offers valuable additional information. Conversely, recEm18-ELISA appears as the currently best serological tool to monitor a regressive and putatively curative course of AE in treated patients.

Humoral immune response to repeated lumpy skin disease virus vaccination and performance of serological tests

BackgroundIn the presented study we investigated the development of the humoral immune response against LSDV during the process of re-vaccination of cattle over a time span of 5 months. In addition, the performance of different serological techniques for antibody detection against LSDV was compared. For sample collection, an area without previous LSD outbreak reports in Serbia was selected. Seventy-nine cattle from twenty farms vaccinated in 2016 and re-vaccinated in 2017 were included in the study. Two farms from the same area with good calving management were selected for investigation of passive LSDV antibody transfer from vaccinated mothers to new-borne calves.ResultsAll investigated cattle were healthy on the day of vaccination and during the whole study. Swelling at the injection site or other side effects of vaccination did not occur after re-vaccination in the study.Detection of LSD-specific antibodies was performed with the standard serological methods VNT and IFAT as well as a commercially available Capripox double antigen multi-species-ELISA. Capripoxvirus-specific antibodies were detected 46 to 47 weeks after vaccination in 2016, with VNT in 35.06% and with IFAT and ELISA in 33.77%. A secondary response was observed in all three tests 1 month after re-vaccination with a significant increase in seropositive animals compared to the results before re-vaccination. With all applied serological methods, the number of animals testing positive was significantly higher at 1 and 5 months post re-vaccination than before re-vaccination. No significant statistical difference (p > 0.05) was observed between the results of all three tests used. The sensitivity and specificity of ELISA was estimated to be SeELISA 91% and SpELISA 87% calculated by the results of VNT and SeELISA 88% and SpELISA 76% calculated by the results of IFAT. Passive antibody transfer from vaccinated mothers to new-born calves was investigated at 14 days after birth. Discrepancies for the detection of LSDV specific antibodies between cows and newborn calves at the age of 14 days were observed in VNT and IFAT, but not in ELISA.ConclusionOf all tests used the commercially available ELISA shows to be the most useful for high throughput analysis compared to VNT or IFAT.

Transfusion Reaction Serology: Results of Applied Practices

Introduction: Serologic testing of post-transfusion reaction specimens aims to ascertain potentially accountable immune hemolytic incompatibility. With the exception of low-risk fevers or uncomplicated allergic reactions (ie- reactions with a likelihood of incompatibility that is deemed too low to justify testing), all transfusion reactions undergo serologic investigation as a matter of local institutional policy. However, compliance with guidelines, and the yields of testing according to reaction types, remain unknown. These measures may indicate the quality of applied practice, and provide evidence for maintaining (or changing) investigation algorithms.Study Design and Methods: Interrogation of two hemovigilance databases identified all possible-to-definite transfusion reactions over a 4-year period (2013-2016) at four academic hospitals (with 1493 adult-care beds). The performance and outcome of reaction-oriented serology were assessed by site, year, reaction type, implicated product, and patient location. Serologic testing of transfusion reaction samples entailed the performance (and pre-transfusion comparison) of grouping (ABO, RHD type) and red cell antibody screening (indirect antiglobulin testing [IAT]), with a post-transfusion Coomb's/direct antiglobulin test [DAT]. Appropriate reflex tests (elutions, panel investigations, or IAT re-crossmatching) proceeded from pertinent positives. Allergic reactions were “complicated” if significant vital sign changes occurred, while fevers were “high-risk” (HRF) if symptomatic or if the Tmax rose to ≥39⁰C. Cardiorespiratory reactions (CRR) involved symptomatic and/or objective disturbances in heart/lung function, while unclassifiable presentations (changes in sensorium or non-precordial pain) were placed in an atypical/“other” category for analysis.Results: Sites received 338-367 reaction referrals per year. By referral proportions (and with overlaps), fevers accounted for 47% of events, allergic disturbances for 40%, and CRR events for 37%, with unclassifiable reactions in 7% (Table). Serologic examination occurred in 773 (55%) of 1412 referrals (of which 1346 were deemed to be transfusion-attributable disturbances, among 1119 unique recipients). The majority of cases (1153 or 82%) were compliant with guidelines. Similar proportions deviated to over-testing (85/550 [15%]) as to under-testing (174/862 [20%]). Overall, 34 (4.4%) of 773 cases yielded a new finding, with 6 (0.8%) reflecting (new or recrudescent) host-derived anti-erythrocyte antibodies, for a number-needed-to-test (NNT) of 129. Serologic yields occurred in all categories where testing was mandated, with most yields (62% or 26/42) owing to HRF and CRR events. Whereas these were often non-ABO (minor antigen-targeting) antibodies (76% or 25/33) and followed reactions to red blood cell transfusions (RBC), the yields from complicated allergic reactions and “other” reactions were entirely due to passively acquired isoagglutinins (11/11). The former non-ABO antibodies were revealed by IAT (with no additional gains from elution studies), while ABO isoagglutinins were revealed by DAT alone (and type-specific eluates), and followed plasma (antibody-) containing products. IVIG-associated reactions exhibited the highest serologic yields (in 48% of cases, or in 70% of non-O type recipients), with 60% experiencing some degree of hemolysis.Conclusion: A fifth of reactions were either over-tested or under-tested. Analysis of the performance and contextual yields of serologic tests revealed that certain products and presentations merit greater attention while others merit less. The IAT is a greater priority than the DAT in HRF and CRR following RBC, while the DAT alone is informative in isoagglutinin-risk cases, irrespective of presentation type, and with predictable eluate specificities. A re-evaluation of traditional serologic testing reflexes may reduce costs and allow re-investment in other more informative reaction-specific assays. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Screening for neurocysticercosis in internationally adopted children: yield, cost and performance of serological tests, Italy, 2001 to 2016

IntroductionNeurocysticercosis (NCC) is one of the leading causes of epilepsy worldwide. The majority of cases in Europe are diagnosed in immigrants. Currently in Italy, routine serological screening for cysticercosis is recommended for internationally adopted children (IAC) coming from endemic countries. Methods: We retrospectively analyse the results of the serological screening for cysticercosis in IAC 16 years old or younger, attending two Italian third level paediatric clinics in 2001–16. Results: Of 2,973 children included in the study, 2,437 (82.0%) were screened by enzyme-linked immune electro transfer blot (EITB), 1,534 (51.6%) by ELISA, and 998 (33.6%) by both tests. The seroprevalence of cysticercosis ranged between 1.7% and 8.9% according to EITB and ELISA, respectively. Overall, 13 children were diagnosed with NCC accounting for a NCC frequency of 0.4% (95% confidence interval (CI): 0.2–0.6%). Among the 168 seropositive children, only seven (4.2%) were diagnosed with NCC. Of these children, three were asymptomatic and four presented epilepsy. Among seronegative children (n = 2,805), seven presented with neurological symptoms that lead to the diagnosis of NCC in six cases. The sensitivity, specificity, positive and negative predictive value for the diagnosis of NCC were 54.5%, 98.6%, 14.6%, 99.8% for EITB and 22.2%, 91.1%, 1.4%, 99.5% for ELISA. The yield of the screening programme was 437 NCC cases per 100,000. The number needed to screen to detect one NCC case was 228. The cost per NCC case detected was EUR 10,372. Conclusion: On the base of our findings we suggest the ongoing serological screening for cysticercosis to be discontinued, at least in Italy, until further evidence in support will be available.

Whole genome sequencing and phylogenetic analysis of strains of the agent of Lyme disease Borrelia burgdorferi from Canadian emergence zones

Lyme disease is emerging in southern Canada due to range expansion of the tick vector, followed by invasion of the agent of Lyme disease Borrelia burgdorferi sensu stricto. Strain diversity, as determined by Multi Locus Sequence Typing, occurs in this zone of emergence, and this may have its origins in adaptation to ecological niches, and have phenotypic consequences for pathogenicity and serological test performance. Sixty-four unique strains were cultured from ticks collected in southern Canada and the genomes sequenced using the Illumina MiSeq platform. A maximum likelihood phylogenetic tree of the chromosome revealed two large clades with multiple subclades. Consistent with previous studies on this species, the clades were not geographically defined, and some Canadian strains were highly divergent from previously sequenced US strains. There was evidence for recombination in the chromosome but this did not affect the phylogeny. Analysis of chromosomal genes indicated that these are under intense purifying selection. Phylogenies of the accessory genome and chromosome were congruent. Therefore strain differences identified in the phylogeny of chromosomal genes likely act as a proxy for genetic determinants of phenotypic differences amongst strains that are harboured in the accessory genome. Further studies on health implications of strain diversity are needed.

IMPACT OF MULTIPLEX PCR IN REDUCING THE RISK OF RESIDUAL TRANSFUSION-TRANSMITTED HUMAN IMMUNODEFICIENCY AND HEPATITIS B AND C VIRUSES IN BURKINA FASO

Background and ObjectiveThe improved performance of serological tests has significantly reduced the risk of human immunodeficiency and hepatitis B and C viruses transmission by blood transfusion, but there is a persistence of residual risk. The objective of this study was to evaluate the impact of multiplex PCR in reducing the risk of residual transmission of these viruses in seronegative blood donors in Burkina Faso.MethodsThis cross-sectional study was conducted from March to September 2017. The serological tests were performed on sera using ARCHITECTSR i1000 (Abbot diagnosis, USA). Detection of viral nucleic acids was performed by multiplex PCR on mini-pools of seronegative plasma for HBV, HCV and HIV using SaCycler-96 Real Time PCR v.7.3 (Sacace Biotechnologies). Multiplex PCR-positive samples from these mini-pools were then individually tested by the same method.ResultsA total of 989 donors aged 17 to 65 were included in the present study. “Repeat donors” accounted for 44.79% (443/989). Seroprevalences for HIV, HBV, and HCV were 2.53% (25/989), 7.28% (72/989) and 2.73% (27/989), respectively. Of the 14 co-infections detected, HBV/HCV was the most common with 0.71% (7/989) of cases. Of 808 donations tested by multiplex PCR, 4.70% (38/808) were positive for HBV while no donation was positive for HIV or HCV.ConclusionOur study showed a high residual risk of HBV transmission through blood transfusion. Due to the high prevalence of blood-borne infections in Burkina Faso, we recommend the addition of multiplex PCR to serologic tests for optimal blood donation screening.