Comparison of commercial methods of immunoblot, ELISA, and chemiluminescent immunoassay for detecting type-specific herpes simplex viruses-1 and -2 IgG

Diagnosis of Herpes Simplex Virus: Laboratory and Point-of-Care Techniques

Herpes is a widespread viral infection caused by the herpes simplex virus (HSV) that has no permanent cure to date. There are two subtypes, HSV-1 and HSV-2, that are known to cause a variety of symptoms, ranging from acute to chronic. HSV is highly contagious and can be transmitted via any type of physical contact. Additionally, viral shedding can also happen from asymptomatic infections. Thus, early and accurate detection of HSV is needed to prevent the transmission of this infection. Herpes can be diagnosed in two ways, by either detecting the presence of the virus in lesions or the antibodies in the blood. Different detection techniques are available based on both laboratory and point of care (POC) devices. Laboratory techniques include different biochemical assays, microscopy, and nucleic acid amplification. In contrast, POC techniques include microfluidics-based tests that enable on-spot testing. Here, we aim to review the different diagnostic techniques, both laboratory-based and POC, their limits of detection, sensitivity, and specificity, as well as their advantages and disadvantages.

Crimean-Congo haemorrhagic fever (CCHF) virus-specific antibody detection in blood donors, Castile-León, Spain, summer 2017 and 2018

BackgroundCrimean-Congo haemorrhagic fever virus (CCHFV) is considered an emerging or even a probable re-emerging pathogen in southern Europe. Presence of this virus had been reported previously in Spain in 2010.AimWe aimed to evaluate the potential circulation of CCHFV in western Spain with a serosurvey in asymptomatic adults (blood donors).MethodsDuring 2017 and 2018, we conducted a CCHFV serosurvey in randomly selected asymptomatic blood donors from western Spain. Three assays using specific IgG antibodies against CCHFV were performed: the VectoCrimea ELISA test, an in-house ELISA and indirect immunofluorescence (EuroImmun) test with glycoprotein and nucleoprotein.ResultsA total of 516 blood donors participated in this cross-sectional study. The majority of the study participants were male (68.4%), and the mean age was 46.3 years. Most of the participants came from rural areas (86.8%) and 68.6% had contact with animals and 20.9% had animal husbandry practices. One in five participants (109/516, 21.1%) were engaged in at-risk professional activities such as agriculture and shepherding, slaughtering, hunting, veterinary and healthcare work (mainly nursing staff and laboratory technicians). A total of 15.3% of the participants were bitten by ticks in the days or months before the date of sampling. We detected anti-CCHFV IgG antibodies with two diagnostic assays in three of the 516 individuals and with one diagnostic assay in six of the 516 individuals.ConclusionSeroprevalence of CCHFV was between 0.58% and 1.16% in Castile-León, Spain. This is the first study in western Spain that showed circulation of CCHFV in healthy people.

Determination of SARS-CoV-2 antibodies with assays from Diasorin, Roche and IDvet

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The sensitivity and specificity of seven serological assays for SARS-CoV-2 were compared.

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No single assay offered a combination of very high sensitivity and very high specificity.

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To maximize sensitivity and specificity two assays should be combined.

There is an ongoing need for highly reliable serological assays to detect individuals with past SARS-CoV-2 infection. Using 75 sera from patients tested positive or negative by SARS-CoV-2 PCR, we investigated the sensitivity and specificity of the Liaison SARS-CoV-2 S1/S2 IgG assay (DiaSorin), the Elecsys Anti-SARS-CoV-2 assay (Roche), and the ID Screen SARS-CoV-2-N IgG indirect kit (IDVet). We determined a sensitivity of 95.5 %, 95.5 %, and 100 % and a specificity of 90.5 %, 96.2 %, and 92.5 % for the DiaSorin assay, the Roche assay, and the IDVet assay, respectively. We conclude that serologic assays combining very high sensitivity and specificity are still not commercially available for SARS-CoV-2. For maximizing sensitivity and specificity of SARS-CoV-2 serological diagnostics, the combination of two assays may be helpful.

Performance evaluation of serological assays to determine the immunoglobulin status in SARS-CoV-2 infected patients

Background

Serological assays for the determination of the immune status of patients that have tested positive for infection with SARS-CoV-2 by RT-PCR are required for, e.g., contact tracing and epidemiological studies. However, data concerning the performance parameters of commercially available high-throughput ELISA tests are still not available on a large scale.

Study design

In our study, we have evaluated an in-house developed ELISA for the detection of the immunoglobulin classes A, G and M directed against the full-length spike glycoprotein from SARS-CoV-2. For this analysis, we have included 110 sera from patients presenting with COVID-19 symptoms or blood donors without symptoms collected at the Austrian Red Cross, Blood Transfusion Service for Upper Austria, Linz. In addition, we have selected four commercially available IgG-based ELISAs as well as one IgA/IgG-based ELISA for the detection of SARS-CoV-2 antigens as well as a multiplexed IgG-based micro-ELISA assay developed for rapid Point of Care testing applications.

Conclusions

All assays evaluated in the course of this study demonstrated suitable sensitivity and specificity values for the identification of patients that have experienced a past infection with SARS-CoV-2. However, testing for the presence of additional immunoglobulins (IgA and IgM) as well as using combinations of different viral antigens is highly advised to improve the predictive values of serological assays.

Comparison of four new commercial serologic assays for determination of SARS-CoV-2 IgG

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4 new SARS-CoV-2 IgG assays can identify individuals with past SARS-CoV-2 infection.

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Combination of two different assays may increase sensitivity and specificity.

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Two assays were identified allowing quantification over a broad linear range.

Background

Facing the ongoing pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), there is an urgent need for serological assays identifying individuals with past coronavirus disease 2019 (COVID-19).

Study design

Our study is the first to compare four new commercially available assays using 75 sera from patients tested positive or negative by SARS-CoV-2 PCR: the anti SARS-CoV-2 ELISA (IgG) (Euroimmun, Germany), the EDI New Coronavirus COVID-19 IgG ELISA, (Epitope diagnostics (EDI), USA), the recomWell SARS-CoV-2 IgG ELISA (Mikrogen, Germany), and the SARS-CoV-2 Virachip IgG (Viramed, Germany).

Results

We found a sensitivity of 86.4 %, 100 %, 86.4 %, and 77.3 % and a specificity of 96,2 %, 88,7 %, 100 %, and 100 % for the Euroimmun assay, the EDI assay, the Mikrogen assay, and the Viramed assay, respectively.

Conclusions

Commercially available SARS-CoV-2 IgG assays have a sufficient specificity and sensitivity for identifying individuals with past SARS-CoV-2 infection.

Validation of an immunoblot assay employing an objective reading system and used as a confirmatory test in equine infectious anaemia surveillance programs

Equine infectious anaemia (EIA) is a blood borne disease that is listed among the notifiable diseases of the World Organisation for Animal Health (OIE). EIA is also regulated by the OIE for the international trading provisions and is generally subject to control programmes. Since 2011, Italy has been conducting a surveillance plan based on a three-tier diagnostic system, using a serological ELISA as screening test, an agar gel immunodiffusion test (AGIDT) as a confirmatory method, and an immunoblot (IB) as an alternative confirmatory assay for discordant results between the first two tests. As for the in-house competitive ELISA (c-ELISA) and the AGIDT, the Italian National Reference Laboratory for EIA (NRL) validated the IB according to the OIE guidelines, employing eight panels containing positive sera, including those from EIA virus (EIAV) proven infected horses, and negative horse, mule and donkey sera collected from different geographical areas. In addition, two international reference image panels were employed for the optimization and the validation of the digital image reading system adopted that allows an impartial measurement of the serum reactivity in the IB assay. The immunological reactivity to EIAV antigens, p26, gp45 and gp90 adsorbed on the IB membrane, determines the serological status of the animal and for EIA, a p26 positive band together with at least one of the other antigen defines a subject as serologically positive for EIAV. For validation, the parameters assessed were threshold values, analytical and diagnostic sensitivity and specificity, repeatability and reproducibility. These parameters were evaluated for each antigen as well as in combination, according to the diagnostic algorithm established above. The validation data defined the IB as having a satisfactory sensitivity, specificity, repeatability and reproducibility for all antigens and species tested. An instrumental recording of the results improves the confidence in using IB as a confirmatory test for EIAV, differently from the AGIDT that is read by an operator. The advantages of using the IB are its higher sensitivity, to that of the AGIDT, which allows an earlier detection of infection that reduces the risk of transmission and therefore the incidence of the EIA, and its higher specificity to that of the ELISA which is based on the discrimination of subjects reacting only against the p26, the antigen used by all ELISAs available, which are not considered as infected by EIAV. In particular, when this assay is used in outbreaks it can detect new cases earlier than the AGIDT, and therefore reduce the restriction period with an economic benefit for the animal owners and the public veterinary sanitary system.

Genital ulcers caused by herpes simplex virus

Genital herpes is a sexually transmitted disease caused by herpes simplex virus type1 (HSV-1) and type2 (HSV-2) belonging to the alphaherpesvirus family, that includes the varicella zoster virus. HSV infection continues to be the most common cause of vulvar ulcers among the sexually active population. Its incidence increases every year. This review summarises the microbiology of the virus, pathogenesis and infection in genitalia, clinical manifestations and correct identification, the different laboratory diagnostic methods, and choice of the correct treatment according to the first infection, recurrence or special cases. Finally, the cost of routine herpes simplex virus infection is analysed.

Comparison of commercial methods of immunoblot, ELISA, and chemiluminescent immunoassay for detecting type-specific herpes simplex viruses-1 and -2 IgG

BACKGROUND

Serology for type-specific herpes simplex virus (HSV) is based on the use of the respective glycoprotein G (gG).

METHODS

Chemiluminescent immunoassay (CLIA; BIO-FLASH^® , Biokit, Spain), ELISA (HerpeSelect^® , Focus, USA), and immunoblot (IB; Virotech, Germany) for detecting HSV-1- and HSV-2-specific IgG were compared using 384 serum samples received for HSV serology. The samples were classified as positive or negative according to a consensus criterion.

RESULTS

For HSV-1, 262 samples were positive and 118 were negative (four samples were unclassifiable). IB showed agreement, sensitivity, and specificity values of 98.68%, 98.47% and 99.15%, respectively. The corresponding figures for CLIA and ELISA were 98.95%, 99.24% and 98.31%, and 98.16%, 99.62% and 94.92%, respectively. For HSV-2, 106 samples were positive and 278 were negative. Agreement, sensitivity, and specificity of IB were 99.48%, 98.11%, and 100%, respectively. The corresponding figures for CLIA and ELISA were 99.48%, 99.06% and 99.64%, and 98.18%, 99.06% and 97.84%, respectively.

CONCLUSION

The three methods showed excellent and equivalent performance characteristics for the detection of type-specific IgG to HSV-1 and HSV-2.