Harmonization of Zika serological assays and comparative evaluation of two commercial ZIKA IgG ELISA kits

The interpretation for Zika virus serology results is challenging due to high antibody cross reactivity with other flaviviruses. This limits availability of reliable and accurate methods for serosurveillance studies to understand the disease burden. Therefore, we conducted study to harmonize anti-Zika IgG antibody detection assays with 1st WHO International Standard (16/352) and working standard (16/320) for anti-Zika virus antibody.Additionally, evaluated NuGenTMZIKA-IgG and NovaLisa®ZIKA virus IgG-Capture ELISA using a panel of 278 seraFurther, 106 samples positive for other-flavi viruses were taken for assessing cross-reactivity of the assay, all serums were further tested by Zika-PRNT. The results of this study indicates satisfactory performance of both the assays. Serological and neutralization assays were calibrated according to the international standards. This will help in understanding antibody dynamics in serosurveillance and vaccine studies. However the performance of the kits with possibilities of cross-reactivity will have to be verified by coupling ZIKV and DENV specific ELISA.

Retrospective comparison of false-positive result frequencies of 3 syphilis serology screening tests in pregnant and nonpregnant patients at an academic medical center in Appalachia

OBJECTIVE

This study retrospectively compared false-positive result frequencies of 3 syphilis serology screening tests and assessed whether false positivity was associated with pregnancy and age.

METHODS

Results for 3 screening tests were retrieved from the laboratory database, including rapid plasma reagin (RPR) assay between October 2016 and September 2019, BioPlex 2200 Syphilis Total immunoassay between May 2020 and January 2022, and Alinity i Syphilis TP assay between February 2022 and April 2023. The false-positive result frequencies were calculated based on testing algorithm criteria.

RESULTS

False-positive result frequency for BioPlex was 0.61% (90/14,707), significantly higher than 0.29% (50/17,447) for RPR and 0.38% (55/14,631) for Alinity (both P < .01). Patients with false-positive results were significantly older than patients with nonreactive results for RPR (median age: 36 vs 28, P < .001), but not for BioPlex or Alinity. For all 3 tests, the positive predictive values in pregnant women were lower than those in nonpregnant women or men. However, pregnant women did not exhibit a higher false-positive result frequency.

CONCLUSION

Although false-positive result frequencies were low overall for all 3 syphilis serology tests, there is a significant difference between different tests. Pregnancy was not associated with more false-positive results for all 3 tests.

Refining Timely Diagnosis of Early Syphilis by Using Treponema pallidum PCR or IgM Immunoblotting Next to Conventional Serology for Syphilis

Treponema pallidum subsp. pallidum is a fastidious spirochete and the etiologic agent of syphilis, a sexually transmitted infection (STI). Syphilis diagnoses and disease staging are based on clinical findings and serologic testing. Moreover, according to most international guidelines, PCR analysis of swab samples from genital ulcers is included in the screening algorithm where possible. It has been suggested that PCR might be omitted from the screening algorithm due to low added value. As an alternative to PCR, IgM serology might be used. In this study, we wanted to establish the added value of PCR and IgM serology for diagnosing primary syphilis. Added value was defined as finding more cases of syphilis, preventing overtreatment, or limiting the extent of partner notification to more recent partners. We found that both PCR and IgM immunoblotting could aid the timely diagnosis of early syphilis in ~24% to 27% of patients. PCR has the greatest sensitivity and can be applied to cases with an ulcer with suspected reinfection or primary infection. In the absence of lesions, the IgM immunoblot could be used. However, the IgM immunoblot has better performance in cases with suspected primary infection than in reinfections. The target population, testing algorithm, time pressures, and costs should determine whether either test provides sufficient value to be implemented in clinical practice.

In a search of a protective titer: Do we or do we not need to know?

The level of postvaccine protection depends on two factors: antibodies and T-cell responses. While the first one is relatively easily measured, the measuring of the second one is a difficult problem. The recent studies indicate that the first one may be a good proxy for the protection, at least for SARS-CoV-2. The massive data currently gathered by both researcher and citizen scientists may be pivotal in confirming this observation, and the collective body of evidence is growing daily. This leads to an acceptance of IgG antibody levels as an accessible biomarker of individual's protection. With enormous and immediate need for assessing patient condition at the point of care, quantitative antibody analysis remains the most effective and efficient way to assess the protection against the disease. Let us not discount importance of reference points in the turmoil of current pandemics.

Evaluation of commercial SARS-CoV-2 serological assays in Canadian public health laboratories

The COVID-19 pandemic has led to the influx of immunoassays for the detection of antibodies towards severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the global market. The Canadian Public Health Laboratory Network Serology Task Force undertook a nationwide evaluation of twelve laboratory and 6 point-of-care based commercial serological assays for the detection of SARS-CoV-2 antibodies. We determined that there was considerable variability in the performance of individual tests and that an orthogonal testing algorithm should be prioritized to maximize the accuracy and comparability of results across the country. The manual enzyme immunoassays and point-of-care tests evaluated had lower specificity and increased coefficients of variation compared to automated enzyme immunoassays platforms putting into question their utility for large-scale sero-surveillance. Overall, the data presented here provide a comprehensive approach for applying accurate serological assays for longitudinal sero-surveillance and vaccine trials while informing Canadian public health policy.

SARS-CoV-2 antibody persistence in COVID-19 convalescent plasma donors: Dependency on assay format and applicability to serosurveillance

BACKGROUND

Antibody response duration following severe acute respiratory syndrome coronavirus 2 infection tends to be variable and depends on severity of disease and method of detection.

STUDY DESIGN AND METHODS

COVID-19 convalescent plasma from 18 donors was collected longitudinally for a maximum of 63-129 days following resolution of symptoms. All the samples were initially screened by the Ortho total Ig test to confirm positivity and subsequently tested with seven additional direct sandwich or indirect binding assays (Ortho, Roche, Abbott, Broad Institute) directed against a variety of antigen targets (S1, receptor binding domain, and nucleocapsid [NC]), along with two neutralization assays (Broad Institute live virus PRNT and Vitalant Research Institute [VRI] Pseudovirus reporter viral particle neutralization [RVPN]).

RESULTS

The direct detection assays (Ortho total Ig total and Roche total Ig) showed increasing levels of antibodies over the time period, in contrast to the indirect IgG assays that showed a decline. Neutralization assays also demonstrated declining responses; the VRI RVPN pseudovirus had a greater rate of decline than the Broad PRNT live virus assay.

DISCUSSION

These data show that in addition to variable individual responses and associations with disease severity, the detection assay chosen contributes to the heterogeneous results in antibody stability over time. Depending on the scope of the research, one assay may be preferable over another. For serosurveillance studies, direct, double Ag-sandwich assays appear to be the best choice due to their stability; in particular, algorithms that include both S1- and NC-based assays can help reduce the rate of false-positivity and discriminate between natural infection and vaccine-derived seroreactivity.

Challenges of Rabies Serology: Defining Context of Interpretation

The case fatality rate of rabies, nearly 100%, is one of the most unique characteristic of this ancient virus infection. The crucial role rabies virus neutralizing antibody plays in protection is both well established and explanation of why rabies serology is important. Various laboratory methods can and have been used but serum neutralization methods have long been the gold standard due to the ability to measure function (neutralization), however these methods can be difficult to perform for several reasons. Assays such as enzyme linked absorbance assays (ELISA), indirect fluorescence antibody (IFA) and more recently lateral flow methods are in use. Interpretation of results can be problematic, not only between methods but also due to modifications of the same method that can lead to misinterpretations. A common assumption in review of laboratory test results is that different methods for the same component produce comparable results under all conditions or circumstances. Assumptions and misinterpretations provide the potential for detrimental decisions, ranging from regulatory to clinically related, and most importantly what ‘level’ is protective. Review of the common challenges in performance and interpretation of rabies serology and specific examples illuminate critical issues to consider when reviewing and applying results of rabies serological testing.

Diagnostic value of serological and molecular biological tests for infectious mononucleosis by EBV in different age stages and course of the disease

Epstein-Barr virus (EBV)-based serologic antibody and viral nucleic acid assays have been found to be feasible means to diagnose infectious mononucleosis (IM) caused by EBV in children. In this study, we will further explore their diagnostic value for IM by EBV in different age stages and over the course of the disease. A collection of 616 children from clinically suspected IM cases was studied. Indirect immunofluorescence (IIF) for EBV-specific antibody (Euroimmun) combined with plasma EB viral nucleic acid assay (real-time fluorescence quantitative polymerase chain reaction reverse-transcription polymerase chain reaction) were used as reference methods. The diagnostic efficiency of the peripheral blood routine test, serologic antibody test, and plasma EB viral nucleic acid assay for the diagnosis of IM was evaluated, respectively. The sensitivity, specificity, Youden' index and the area under curve (AUC) were 93.08%, 87.77%, 0.81 and 0.904 (95% confidence interval [CI]: 0.878-0.931) for the peripheral lymphocyte test (lymphocytosis > 5 × 109 /L), 98.27%, 91.13%, 0.89 and 0.947 (95% CI: 0.927-0.967) for the plasma EBV-DNA test, and 84.08%, 96.33%, 0.80 and 0.902 (95% CI: 0.874-0.930) for the EBV viral capsid antigen (VCA)-IgG avidity test. The plasma EBV-DNA test has a higher diagnostic value than the VCA-IgG avidity test in children aged <6 years, especially aged <3 years; the peripheral lymphocyte test and plasma EBV-DNA test are suitable for the early stage of the disease, while the VCA-IgG avidity test for after 7 days of the disease. EBV antibody detection (IIF) should be combined with EBV nucleic acid detection in children age <6 years and the early stage of the disease.

External quality assessment of Rift Valley fever diagnosis in countries at risk of the disease: African, Indian Ocean and Middle-East regions

Rift Valley fever virus (RVFV), an arbovirus belonging to the Phlebovirus genus of the Phenuiviridae family, causes the zoonotic and mosquito-borne RVF. The virus, which primarily affects livestock (ruminants and camels) and humans, is at the origin of recent major outbreaks across the African continent (Mauritania, Libya, Sudan), and in the South-Western Indian Ocean (SWIO) islands (Mayotte). In order to be better prepared for upcoming outbreaks, to predict its introduction in RVFV unscathed countries, and to run efficient surveillance programmes, the priority is harmonising and improving the diagnostic capacity of endemic countries and/or countries considered to be at risk of RVF. A serological inter-laboratory proficiency test (PT) was implemented to assess the capacity of veterinary laboratories to detect antibodies against RVFV. A total of 18 laboratories in 13 countries in the Middle East, North Africa, South Africa, and the Indian Ocean participated in the initiative. Two commercial kits and two in-house serological assays for the detection of RVFV specific IgG antibodies were tested. Sixteen of the 18 participating laboratories (88.9%) used commercial kits, the analytical performance of test sensitivity and specificity based on the seroneutralisation test considered as the reference was 100%. The results obtained by the laboratories which used the in-house assay were correct in only one of the two criteria (either sensitivity or specificity). In conclusion, most of the laboratories performed well in detecting RVFV specific IgG antibodies and can therefore be considered to be prepared. Three laboratories in three countries need to improve their detection capacities. Our study demonstrates the importance of conducting regular proficiency tests to evaluate the level of preparedness of countries and of building a network of competent laboratories in terms of laboratory diagnosis to better face future emerging diseases in emergency conditions.

Different Cross-Reactivities of IgM Responses in Dengue, Zika and Tick-Borne Encephalitis Virus Infections

Flaviviruses circulate worldwide and cause a number of medically relevant human diseases, such as dengue, Zika, yellow fever, and tick-borne encephalitis (TBE). Serology plays an important role in the diagnosis of flavivirus infections, but can be impeded by antigenic cross-reactivities among flaviviruses. Therefore, serological diagnosis of a recent infection can be insufficiently specific, especially in areas where flaviviruses co-circulate and/or vaccination coverage against certain flaviviruses is high. In this study, we developed a new IgM assay format, which is well suited for the specific diagnosis of TBE, Zika and dengue virus infections. In the case of TBE and Zika, the IgM response proved to be highly specific for the infecting virus. In contrast, primary dengue virus infections induced substantial amounts of cross-reactive IgM antibodies, which is most likely explained by structural peculiarities of dengue virus particles. Despite the presence of cross-reactive IgM, the standardized nature and the quantitative read-out of the assay even allowed the serotype-specific diagnosis of recent dengue virus infections in most instances.

Analysis of false-negative rapid diagnostic tests for symptomatic malaria in the Democratic Republic of the Congo

The majority of Plasmodium falciparum malaria diagnoses in Africa are made using rapid diagnostic tests (RDTs) that detect histidine-rich protein 2. Increasing reports of false-negative RDT results due to parasites with deletions of the pfhrp2 and/or pfhrp3 genes (pfhrp2/3) raise concern about existing malaria diagnostic strategies. We previously identified pfhrp2-negative parasites among asymptomatic children in the Democratic Republic of the Congo (DRC), but their impact on diagnosis of symptomatic malaria is unknown. We performed a cross-sectional study of false-negative RDTs in symptomatic subjects in 2017. Parasites were characterized by microscopy; RDT; pfhrp2/3 genotyping and species-specific PCR assays; a bead-based immunoassay for Plasmodium antigens; and/or whole-genome sequencing. Among 3627 symptomatic subjects, 427 (11.8%) had RDT-/microscopy + results. Parasites from eight (0.2%) samples were initially classified as putative pfhrp2/3 deletions by PCR, but antigen testing and whole-genome sequencing confirmed the presence of intact genes. 56.8% of subjects had PCR-confirmed malaria. Non-falciparum co-infection with P. falciparum was common (13.2%). Agreement between PCR and HRP2-based RDTs was satisfactory (Cohen's kappa = 0.66) and superior to microscopy (0.33). Symptomatic malaria due to pfhrp2/3-deleted P. falciparum was not observed. Ongoing HRP2-based RDT use is appropriate for the detection of falciparum malaria in the DRC.

Heterogeneity in response to serological exposure markers of recent Plasmodium vivax infections in contrasting epidemiological contexts

BACKGROUND

Antibody responses as serological markers of Plasmodium vivax infection have been shown to correlate with exposure, but little is known about the other factors that affect antibody responses in naturally infected people from endemic settings. To address this question, we studied IgG responses to novel serological exposure markers (SEMs) of P. vivax in three settings with different transmission intensity.

METHODOLOGY

We validated a panel of 34 SEMs in a Peruvian cohort with up to three years' longitudinal follow-up using a multiplex platform and compared results to data from cohorts in Thailand and Brazil. Linear regression models were used to characterize the association between antibody responses and age, the number of detected blood-stage infections during follow-up, and time since previous infection. Receiver Operating Characteristic (ROC) analysis was used to test the performance of SEMs to identify P. vivax infections in the previous 9 months.

PRINCIPAL FINDINGS

Antibody titers were associated with age, the number of blood-stage infections, and time since previous P. vivax infection in all three study sites. The association between antibody titers and time since previous P. vivax infection was stronger in the low transmission settings of Thailand and Brazil compared to the higher transmission setting in Peru. Of the SEMs tested, antibody responses to RBP2b had the highest performance for classifying recent exposure in all sites, with area under the ROC curve (AUC) = 0.83 in Thailand, AUC = 0.79 in Brazil, and AUC = 0.68 in Peru.

CONCLUSIONS

In low transmission settings, P. vivax SEMs can accurately identify individuals with recent blood-stage infections. In higher transmission settings, the accuracy of this approach diminishes substantially. We recommend using P. vivax SEMs in low transmission settings pursuing malaria elimination, but they are likely to be less effective in high transmission settings focused on malaria control.

Meta-analysis of diagnostic performance of serology tests for COVID-19: impact of assay design and post-symptom-onset intervals

Serology detection is recognized for its sensitivity in convalescent patients with COVID-19, in comparison with nucleic acid amplification tests (NAATs). This article aimed to evaluate the diagnostic accuracy of serologic methods for COVID-19 based on assay design and post-symptom-onset intervals. Two authors independently searched PubMed, Cochrane library, Ovid, EBSCO for case-control, longitudinal and cohort studies that determined the diagnostic accuracy of serology tests in comparison with NAATs in COVID-19 cases and used QUADAS-2 for quality assessment. Pooled accuracy was analysed using INLA method. A total of 27 studies were included in this meta-analysis, with 4 cohort, 16 case-control and 7 longitudinal studies and 4565 participants. Serology tests had the lowest sensitivity at 0-7 days after symptom onset and the highest at >14 days. TAB had a better sensitivity than IgG or IgM only. Using combined nucleocapsid (N) and spike(S) protein had a better sensitivity compared to N or S protein only. Lateral flow immunoassay (LFIA) had a lower sensitivity than enzyme-linked immunoassay (ELISA) and chemiluminescent immunoassay (CLIA). Serology tests will play an important role in the clinical diagnosis for later stage COVID-19 patients. ELISA tests, detecting TAB or targeting combined N and S proteins had a higher diagnostic sensitivity compared to other methods.

Significance of serology testing to assist timely diagnosis of SARS-CoV-2 infections: implication from a family cluster

Confirmative diagnosis of SARS-CoV-2 infections has been challenged due to unsatisfactory positive rate of molecular assays. Here we identified a family cluster of SARS-CoV-2 infections, with five of six family members were SARS-CoV-2-specific immunoglobin serology testing positive, while molecular assays only detected two of this five patients even repeated twice. We comprehensively analyzed this familial cluster of cases based on the clinical characteristics, chest CT images, SARS-CoV-2 molecular detection results, and serology testing results. At last, two patients were diagnosed with COVID-19, two were suspected of COVID-19, and two were considered close contacts. Our results emphasized the significance of serology testing to assist timely diagnosis of SARS-CoV-2 infections, especially for COVID-19 close contacts screening.

A comparative evaluation between the Abbott Panbio™ COVID-19 IgG/IgM rapid test device and Abbott Architect™ SARS CoV-2 IgG assay

INTRODUCTION

Antibodies to SARS-CoV-2 serve as critical diagnostic markers for determining how broadly the COVID-19 pandemic has spread, confirming patient recovery, monitoring potential long-term effects of infection, and evaluating potential protection from reinfection. As new antibody tests become available, it is important to evaluate their performance and utility. The aim of this study was to compare the performance of the Abbott PanbioTM COVID-19 IgG/IgM Rapid Test Device against the Abbott ArchitectTM SARS CoV-2 IgG Assay for the detection of the COVID-19 IgG antibody.

METHODS

Two panels of specimens were utilized to challenge both antibody tests: (1) a set of 150 prepandemic negative specimens collected in 2014, and (2) a set of 122 specimens from 87 hospitalized COVID-19 patients in the US and UK that were confirmed with a positive SARS-CoV-2 RNA test result.

RESULTS

The ArchitectTM test had a specificity of 100 % and sensitivity of 99.1 % and 93.9 % when excluding or including immunocompromised patients, respectively for specimens collected >14 days post symptom onset or >5 days post-RNA testing. The PanbioTM test had 99.3 % agreement to ArchitectTM. Notably, N = 6 immune-compromised individuals were identified that did not develop detectable antibodies by day 30.

CONCLUSION

There is good concordance between the ArchitectTM SARS CoV-2 IgG Assay and PanbioTM COVID-19 IgG/IgM Rapid Test Device for the detection of SARS CoV-2 IgG.

Diagnostic performances and thresholds: The key to harmonization in serological SARS-CoV-2 assays?

BACKGROUND

The evaluation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific antibody (Ab) assay performances is of the utmost importance in establishing and monitoring virus spread in the community. In this study focusing on IgG antibodies, we compare reliability of three chemiluminescent (CLIA) and two enzyme linked immunosorbent (ELISA) assays.

METHODS

Sera from a total of 271 subjects, including 64 reverse transcription-polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 patients were tested for specific Ab using Maglumi (Snibe), Liaison (Diasorin), iFlash (Yhlo), Euroimmun (Medizinische Labordiagnostika AG) and Wantai (Wantai Biological Pharmacy) assays. Diagnostic sensitivity and specificity, positive and negative likelihood ratios were evaluated using manufacturers' and optimized thresholds.

RESULTS

Optimized thresholds (Maglumi 2 kAU/L, Liaison 6.2 kAU/L and iFlash 15.0 kAU/L) allowed us to achieve a negative likelihood ratio and an accuracy of: 0.06 and 93.5% for Maglumi; 0.03 and 93.1% for Liaison; 0.03 and 91% for iFlash. Diagnostic sensitivities and specificities were above 93.8% and 85.9%, respectively for all CLIA assays. Overall agreement was 90.3% (Cohen's kappa = 0.805 and SE = 0.041) for CLIA, and 98.4% (Cohen's kappa = 0.962 and SE = 0.126) for ELISA.

CONCLUSIONS

The results obtained indicate that, for CLIA assays, it might be possible to define thresholds that improve the negative likelihood ratio. Thus, a negative test result enables the identification of subjects at risk of being infected, who should then be closely monitored over time with a view to preventing further viral spread. Redefined thresholds, in addition, improved the overall inter-assay agreement, paving the way to a better harmonization of serologic tests.

Evaluation of Serological Tests for SARS-CoV-2: Implications for Serology Testing in a Low-Prevalence Setting

BACKGROUND

Robust serological assays are essential for long-term control of the COVID-19 pandemic. Many recently released point-of-care (PoCT) serological assays have been distributed with little premarket validation.

METHODS

Performance characteristics for 5 PoCT lateral flow devices approved for use in Australia were compared to a commercial enzyme immunoassay (ELISA) and a recently described novel surrogate virus neutralization test (sVNT).

RESULTS

Sensitivities for PoCT ranged from 51.8% (95% confidence interval [CI], 43.1%-60.4%) to 67.9% (95% CI, 59.4%-75.6%), and specificities from 95.6% (95% CI, 89.2%-98.8%) to 100.0% (95% CI, 96.1%-100.0%). ELISA sensitivity for IgA or IgG detection was 67.9% (95% CI, 59.4%-75.6%), increasing to 93.8% (95% CI, 85.0%-98.3%) for samples >14 days post symptom onset. sVNT sensitivity was 60.9% (95% CI, 53.2%-68.4%), rising to 91.2% (95% CI, 81.8%-96.7%) for samples >14 days post symptom onset, with specificity 94.4% (95% CI, 89.2%-97.5%).

CONCLUSIONS

Performance characteristics for COVID-19 serological assays were generally lower than those reported by manufacturers. Timing of specimen collection relative to onset of illness or infection is crucial in reporting of performance characteristics for COVID-19 serological assays. The optimal algorithm for implementing serological testing for COVID-19 remains to be determined, particularly in low-prevalence settings.

Improved Detection of Antibodies against SARS-CoV-2 by Microsphere-Based Antibody Assay

Currently available COVID-19 antibody tests using enzyme immunoassay (EIA) or immunochromatographic assay have variable sensitivity and specificity. Here, we developed and evaluated a novel microsphere-based antibody assay (MBA) for detecting immunoglobulin G (IgG) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein (NP) and spike protein receptor binding domain (RBD). The seropositive cutoff value was set using a cohort of 294 anonymous serum specimens collected in 2018. The specificity was assessed using serum specimens collected from organ donors or influenza patients before 2020. Seropositive rate was determined among COVID-19 patients. Time-to-seropositivity and signal-to-cutoff (S/CO) ratio were compared between MBA and EIA. MBA had a specificity of 100% (93/93; 95% confidence interval (CI), 96-100%) for anti-NP IgG, 98.9% (92/93; 95% CI 94.2-100%) for anti-RBD IgG. The MBA seropositive rate for convalescent COVID-19 patients was 89.8% (35/39) for anti-NP IgG and 79.5% (31/39) for anti-RBD IgG. The time-to-seropositivity was shorter with MBA than EIA. MBA could better differentiate between COVID-19 patients and negative controls with higher S/CO ratio for COVID-19 patients, lower S/CO ratio with negative controls and fewer specimens in the equivocal range. MBA is robust, simple and is suitable for clinical microbiology laboratory for the accurate determination of anti-SARS-CoV-2 antibodies for diagnosis, serosurveillance, and vaccine trials.

Types of Assays for SARS-CoV-2 Testing: A Review

Clinical laboratory testing routinely provides actionable results, which help direct patient care in the inpatient and outpatient settings. Since December 2019, a novel coronavirus (SARS-CoV-2) has been causing disease (COVID-19 [coronavirus disease 2019]) in patients, beginning in China and now extending worldwide. In this context of a novel viral pandemic, clinical laboratories have developed multiple novel assays for SARS-CoV-2 diagnosis and for managing patients afflicted with this illness. These include molecular and serologic-based tests, some with point-of-care testing capabilities. Herein, we present an overview of the types of testing available for managing patients with COVID-19, as well as for screening of potential plasma donors who have recovered from COVID-19.

Development of a Sensitive Immunochromatographic Method Using Lanthanide Fluorescent Microsphere for Rapid Serodiagnosis of COVID-19

The SARS-CoV-2 infection that caused the COVID-19 pandemic quickly spread worldwide within two months. Rapid diagnosis of the disease and isolation of patients are effective ways to prevent and control the spread of COVID-19. Therefore, a sensitive immunofluorescent assay method was developed for rapid detection of special IgM and IgG of COVID-19 in human serum within 10 min. The recombinant nucleocapsid protein of 2019 novel coronavirus was used as capture antigen. Lanthanide, Eu(III) fluorescent microsphere, was used to qualitatively/semiquantitatively determine the solid phase immunochromatographic assay. A total of 28 clinical positive and 77 negative serum or plasma samples were included in the test. Based on the analysis of serum or plasma from COVID-19 patients and healthy people, the sensitivity and specificity of the immunochromatographic assay were calculated as 98.72% and 100% (IgG), and 98.68% and 93.10% (IgM), respectively. The results demonstrated that rapid immunoassay has high sensitivity and specificity and was useful for rapid serodiagnosis of COVID-19.

Application of WHO International Biological Reference Standards to evaluate commercial serological tests for chronic Chagas disease

BACKGROUND Chagas disease, resulting from Trypanosoma cruzi infections, continues to be a health concern mainly in Latin American countries where the parasite is endemic. The laboratory diagnosis of a chronic infection is determined through serological assays for antibodies against T. cruzi and several tests are available that differ in key components, formats and methodologies. To date, no single test meets the criteria of a gold standard. The situation is further complicated by the difficulties associated with performance comparisons between different immunoassays or methodologies executed at different times and geographical areas. OBJECTIVE To improve the diagnosis of Chagas disease, the WHO coordinated the development of two International Biological Reference Standards for antibodies against anti-T. cruzi: NIBSC 09/186 and NIBSC 09/188 that respectively represent geographical regions with the highest prevalence of TcII and TcI lineages of the parasite. METHODS The principle goal of this study was to verify the behavior of these standards when assayed by several commercially available serological tests that employ different methods to capture and detect human anti-T. cruzi antibodies. FINDINGS AND MAIN CONCLUSIONS The results reinforce the recommendation that these standards be considered for performance evaluations of commercialised immunoassays and should be an integral step in the development of new test components or assay paradigms.

Heat Inactivation of Different Types of SARS-CoV-2 Samples: What Protocols for Biosafety, Molecular Detection and Serological Diagnostics?

Standard precautions to minimize the risk of SARS-CoV-2 transmission implies that infected cell cultures and clinical specimens may undergo some sort of inactivation to reduce or abolish infectivity. We evaluated three heat inactivation protocols (56 °C-30 min, 60 °C-60 min and 92 °C-15 min) on SARS-CoV-2 using (i) infected cell culture supernatant, (ii) virus-spiked human sera (iii) and nasopharyngeal samples according to the recommendations of the European norm NF EN 14476-A2. Regardless of the protocol and the type of samples, a 4 Log10 TCID50 reduction was observed. However, samples containing viral loads > 6 Log10 TCID50 were still infectious after 56 °C-30 min and 60 °C-60 min, although infectivity was < 10 TCID50. The protocols 56 °C-30 min and 60 °C-60 min had little influence on the RNA copies detection, whereas 92 °C-15 min drastically reduced the limit of detection, which suggests that this protocol should be avoided for inactivation ahead of molecular diagnostics. Lastly, 56 °C-30 min treatment of serum specimens had a negligible influence on the results of IgG detection using a commercial ELISA test, whereas a drastic decrease in neutralizing titers was observed.

Diagnostic accuracy of serological tests for covid-19: systematic review and meta-analysis

OBJECTIVE

To determine the diagnostic accuracy of serological tests for coronavirus disease-2019 (covid-19).

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Medline, bioRxiv, and medRxiv from 1 January to 30 April 2020, using subject headings or subheadings combined with text words for the concepts of covid-19 and serological tests for covid-19.

ELIGIBILITY CRITERIA AND DATA ANALYSIS

Eligible studies measured sensitivity or specificity, or both of a covid-19 serological test compared with a reference standard of viral culture or reverse transcriptase polymerase chain reaction. Studies were excluded with fewer than five participants or samples. Risk of bias was assessed using quality assessment of diagnostic accuracy studies 2 (QUADAS-2). Pooled sensitivity and specificity were estimated using random effects bivariate meta-analyses.

MAIN OUTCOME MEASURES

The primary outcome was overall sensitivity and specificity, stratified by method of serological testing (enzyme linked immunosorbent assays (ELISAs), lateral flow immunoassays (LFIAs), or chemiluminescent immunoassays (CLIAs)) and immunoglobulin class (IgG, IgM, or both). Secondary outcomes were stratum specific sensitivity and specificity within subgroups defined by study or participant characteristics, including time since symptom onset.

RESULTS

5016 references were identified and 40 studies included. 49 risk of bias assessments were carried out (one for each population and method evaluated). High risk of patient selection bias was found in 98% (48/49) of assessments and high or unclear risk of bias from performance or interpretation of the serological test in 73% (36/49). Only 10% (4/40) of studies included outpatients. Only two studies evaluated tests at the point of care. For each method of testing, pooled sensitivity and specificity were not associated with the immunoglobulin class measured. The pooled sensitivity of ELISAs measuring IgG or IgM was 84.3% (95% confidence interval 75.6% to 90.9%), of LFIAs was 66.0% (49.3% to 79.3%), and of CLIAs was 97.8% (46.2% to 100%). In all analyses, pooled sensitivity was lower for LFIAs, the potential point-of-care method. Pooled specificities ranged from 96.6% to 99.7%. Of the samples used for estimating specificity, 83% (10 465/12 547) were from populations tested before the epidemic or not suspected of having covid-19. Among LFIAs, pooled sensitivity of commercial kits (65.0%, 49.0% to 78.2%) was lower than that of non-commercial tests (88.2%, 83.6% to 91.3%). Heterogeneity was seen in all analyses. Sensitivity was higher at least three weeks after symptom onset (ranging from 69.9% to 98.9%) compared with within the first week (from 13.4% to 50.3%).

CONCLUSION

Higher quality clinical studies assessing the diagnostic accuracy of serological tests for covid-19 are urgently needed. Currently, available evidence does not support the continued use of existing point-of-care serological tests.

STUDY REGISTRATION

PROSPERO CRD42020179452.

Expression Analysis and Serodiagnostic Potential of Microneme Proteins 1 and 3 in Eimeria stiedai

Eimeria stiedai is an apicomplexan protozoan parasite that invades the liver and bile duct epithelial cells in rabbits and causes severe hepatic coccidiosis, resulting in significant economic losses in the domestic rabbit industry. Hepatic coccidiosis lacks the typical clinical symptoms and there is a lack of effective premortem tools to timely diagnose this disease. Therefore, in the present study we cloned and expressed the two microneme proteins i.e., microneme protein 1 (EsMIC1) and microneme protein 3 (EsMIC3) from E. stiedai and used them as recombinant antigens to develop a serodiagnostic method for an effective diagnosis of hepatic coccidiosis. The cDNAs encoding EsMIC1 and EsMIC3 were cloned and the mRNA expression levels of these two genes at different developmental stages of E. stiedai were determined by quantitative real-time PCR analysis (qRT-PCR). The immunoreactivity of recombinant EsMIC1 (rEsMIC1) and EsMIC3 (rEsMIC3) proteins were detected by Western blotting, and indirect enzyme-linked immunosorbent assays (ELISAs) based on these two recombinant antigens were established to evaluate their serodiagnostic potential. Our results showed that the proteins encoded by the ORFs of EsMIC1 (711 bp) and EsMIC3 (891 bp) were approximately 25.89 and 32.39 kDa in predicted molecular weight, respectively. Both EsMIC1 and EsMIC3 showed the highest mRNA expression levels in the merozoites stage of E. stiedai. Western blotting analysis revealed that both recombinant proteins were recognized by E. stiedai positive sera, and the indirect ELISAs using rEsMIC1 and rEsMIC3 were developed based on their good immunoreactivity, with 100% (48/48) sensitivity and 97.9% (47/48) specificity for rEsMIC1 with 100% (48/48) sensitivity and 100% (48/48) specificity for rEsMIC3, respectively. Moreover, rEsMIC1- and rEsMIC3-based indirect ELISA were able to detect corresponding antibodies in sera at days 6, 8, and 10 post E. stiedai infection, with the highest positive diagnostic rate (62.5% (30/48) for rEsMIC1 and 66.7% (32/48) for rEsMIC3) observed at day 10 post infection. Therefore, both EsMIC1 and EsMIC3 can be used as potential serodiagnostic candidate antigens for hepatic coccidiosis caused by E. stiedai.

Antibody tests for identification of current and past infection with SARS-CoV-2

BACKGROUND

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and resulting COVID-19 pandemic present important diagnostic challenges. Several diagnostic strategies are available to identify current infection, rule out infection, identify people in need of care escalation, or to test for past infection and immune response. Serology tests to detect the presence of antibodies to SARS-CoV-2 aim to identify previous SARS-CoV-2 infection, and may help to confirm the presence of current infection.

OBJECTIVES

To assess the diagnostic accuracy of antibody tests to determine if a person presenting in the community or in primary or secondary care has SARS-CoV-2 infection, or has previously had SARS-CoV-2 infection, and the accuracy of antibody tests for use in seroprevalence surveys.

SEARCH METHODS

We undertook electronic searches in the Cochrane COVID-19 Study Register and the COVID-19 Living Evidence Database from the University of Bern, which is updated daily with published articles from PubMed and Embase and with preprints from medRxiv and bioRxiv. In addition, we checked repositories of COVID-19 publications. We did not apply any language restrictions. We conducted searches for this review iteration up to 27 April 2020.

SELECTION CRITERIA

We included test accuracy studies of any design that evaluated antibody tests (including enzyme-linked immunosorbent assays, chemiluminescence immunoassays, and lateral flow assays) in people suspected of current or previous SARS-CoV-2 infection, or where tests were used to screen for infection. We also included studies of people either known to have, or not to have SARS-CoV-2 infection. We included all reference standards to define the presence or absence of SARS-CoV-2 (including reverse transcription polymerase chain reaction tests (RT-PCR) and clinical diagnostic criteria).

DATA COLLECTION AND ANALYSIS

We assessed possible bias and applicability of the studies using the QUADAS-2 tool. We extracted 2x2 contingency table data and present sensitivity and specificity for each antibody (or combination of antibodies) using paired forest plots. We pooled data using random-effects logistic regression where appropriate, stratifying by time since post-symptom onset. We tabulated available data by test manufacturer. We have presented uncertainty in estimates of sensitivity and specificity using 95% confidence intervals (CIs).

MAIN RESULTS

We included 57 publications reporting on a total of 54 study cohorts with 15,976 samples, of which 8526 were from cases of SARS-CoV-2 infection. Studies were conducted in Asia (n = 38), Europe (n = 15), and the USA and China (n = 1). We identified data from 25 commercial tests and numerous in-house assays, a small fraction of the 279 antibody assays listed by the Foundation for Innovative Diagnostics. More than half (n = 28) of the studies included were only available as preprints. We had concerns about risk of bias and applicability. Common issues were use of multi-group designs (n = 29), inclusion of only COVID-19 cases (n = 19), lack of blinding of the index test (n = 49) and reference standard (n = 29), differential verification (n = 22), and the lack of clarity about participant numbers, characteristics and study exclusions (n = 47). Most studies (n = 44) only included people hospitalised due to suspected or confirmed COVID-19 infection. There were no studies exclusively in asymptomatic participants. Two-thirds of the studies (n = 33) defined COVID-19 cases based on RT-PCR results alone, ignoring the potential for false-negative RT-PCR results. We observed evidence of selective publication of study findings through omission of the identity of tests (n = 5). We observed substantial heterogeneity in sensitivities of IgA, IgM and IgG antibodies, or combinations thereof, for results aggregated across different time periods post-symptom onset (range 0% to 100% for all target antibodies). We thus based the main results of the review on the 38 studies that stratified results by time since symptom onset. The numbers of individuals contributing data within each study each week are small and are usually not based on tracking the same groups of patients over time. Pooled results for IgG, IgM, IgA, total antibodies and IgG/IgM all showed low sensitivity during the first week since onset of symptoms (all less than 30.1%), rising in the second week and reaching their highest values in the third week. The combination of IgG/IgM had a sensitivity of 30.1% (95% CI 21.4 to 40.7) for 1 to 7 days, 72.2% (95% CI 63.5 to 79.5) for 8 to 14 days, 91.4% (95% CI 87.0 to 94.4) for 15 to 21 days. Estimates of accuracy beyond three weeks are based on smaller sample sizes and fewer studies. For 21 to 35 days, pooled sensitivities for IgG/IgM were 96.0% (95% CI 90.6 to 98.3). There are insufficient studies to estimate sensitivity of tests beyond 35 days post-symptom onset. Summary specificities (provided in 35 studies) exceeded 98% for all target antibodies with confidence intervals no more than 2 percentage points wide. False-positive results were more common where COVID-19 had been suspected and ruled out, but numbers were small and the difference was within the range expected by chance. Assuming a prevalence of 50%, a value considered possible in healthcare workers who have suffered respiratory symptoms, we would anticipate that 43 (28 to 65) would be missed and 7 (3 to 14) would be falsely positive in 1000 people undergoing IgG/IgM testing at days 15 to 21 post-symptom onset. At a prevalence of 20%, a likely value in surveys in high-risk settings, 17 (11 to 26) would be missed per 1000 people tested and 10 (5 to 22) would be falsely positive. At a lower prevalence of 5%, a likely value in national surveys, 4 (3 to 7) would be missed per 1000 tested, and 12 (6 to 27) would be falsely positive. Analyses showed small differences in sensitivity between assay type, but methodological concerns and sparse data prevent comparisons between test brands.

AUTHORS' CONCLUSIONS

The sensitivity of antibody tests is too low in the first week since symptom onset to have a primary role for the diagnosis of COVID-19, but they may still have a role complementing other testing in individuals presenting later, when RT-PCR tests are negative, or are not done. Antibody tests are likely to have a useful role for detecting previous SARS-CoV-2 infection if used 15 or more days after the onset of symptoms. However, the duration of antibody rises is currently unknown, and we found very little data beyond 35 days post-symptom onset. We are therefore uncertain about the utility of these tests for seroprevalence surveys for public health management purposes. Concerns about high risk of bias and applicability make it likely that the accuracy of tests when used in clinical care will be lower than reported in the included studies. Sensitivity has mainly been evaluated in hospitalised patients, so it is unclear whether the tests are able to detect lower antibody levels likely seen with milder and asymptomatic COVID-19 disease. The design, execution and reporting of studies of the accuracy of COVID-19 tests requires considerable improvement. Studies must report data on sensitivity disaggregated by time since onset of symptoms. COVID-19-positive cases who are RT-PCR-negative should be included as well as those confirmed RT-PCR, in accordance with the World Health Organization (WHO) and China National Health Commission of the People's Republic of China (CDC) case definitions. We were only able to obtain data from a small proportion of available tests, and action is needed to ensure that all results of test evaluations are available in the public domain to prevent selective reporting. This is a fast-moving field and we plan ongoing updates of this living systematic review.

Anti-platelet antibody immunoassays in childhood immune thrombocytopenia: a systematic review

BACKGROUND

In adult immune thrombocytopenia (ITP), an acquired autoimmune bleeding disorder, anti-platelet autoantibody testing may be useful as a rule-in test. Childhood ITP has different disease characteristics, and the diagnostic and prognostic value of anti-platelet antibody testing remains uncertain.

OBJECTIVE

To systematically review the diagnostic accuracy of anti-platelet autoantibody testing in childhood ITP.

METHODS

PubMed and EMBASE were searched for studies evaluating immunoassays in childhood ITP. Study quality was assessed (QUADAS2), and evidence was synthesized descriptively.

RESULTS

In total, 40 studies (1606 patients) were identified. Nine studies reported sufficient data to determine diagnostic accuracy measures. Anti-platelet IgG antibody testing showed a moderate sensitivity (0·36-0·80 platelet-associated IgG [direct test]; 0·19-0·39 circulating IgG [indirect test]). In studies that reported control data, including patients with non-immune thrombocytopenia, specificity was very good (0·80-1·00). Glycoprotein-specific immunoassays showed comparable sensitivity (three studies) and predominantly identified IgG anti-GP IIb/IIIa antibodies, with few IgG anti-GP Ib/IX antibodies. Anti-platelet IgM antibodies were identified in a substantial proportion of children (sensitivity 0·62-0·64 for direct and indirect tests).

CONCLUSION

The diagnostic evaluation of IgG and IgM anti-platelet antibodies may be useful as a rule-in test for ITP. In children with insufficient platelets for a direct test, indirect tests may be performed instead. A negative test does not rule out the diagnosis of ITP. Future studies should evaluate the value of anti-platelet antibody tests in thrombocytopenic children with suspected ITP.

SARS-CoV2: Diagnostic tests available to the clinician

On December 2019, a new coronavirus disease (COVID-19) emerged in China and spread worldwide, causing acute severe respiratory syndrome. Due to the increased transmission rate of the virus, it became of great importance the early diagnosis of the disease. The coronavirus pandemic led to the development of numerous tests in order to mass screening population for active viral load and for the identification of antibodies for epidemiological purposes. This review summarizes the different diagnostic tests available to the clinicians for the diagnosis and follow up of the SARS COV-2 infections.

Challenges of Covid-19 testing

No abstract available.

Humanity tested

The world needs mass at-home serological testing for antibodies elicited by SARS-CoV-2, and rapid and frequent point-of-care testing for the presence of the virus’ RNA in selected populations.

Diagnostic performance of COVID-19 serology assays

INTRODUCTION

The World Health Organization (WHO) declared COVID-19 outbreak as a world pandemic on 12th March 2020. Diagnosis of suspected cases is confirmed by nucleic acid assays with real-time PCR, using respiratory samples. Serology tests are comparatively easier to perform, but their utility may be limited by the performance and the fact that antibodies appear later during the disease course. We aimed to describe the performance data on serological assays for COVID-19.

MATERIALS AND METHODS

A review of multiple reports and kit inserts on the diagnostic performance of rapid tests from various manufacturers that are commercially available were performed. Only preliminary data are available currently.

RESULTS

From a total of nine rapid detection test (RDT) kits, three kits offer total antibody detection, while six kits offer combination SARS-CoV-2 IgM and IgG detection in two separate test lines. All kits are based on colloidal gold-labeled immunochromatography principle and one-step method with results obtained within 15 minutes, using whole blood, serum or plasma samples. The sensitivity for both IgM and IgG tests ranges between 72.7% and 100%, while specificity ranges between 98.7% to 100%. Two immunochromatography using nasopharyngeal or throat swab for detection of COVID-19 specific antigen are also reviewed.

CONCLUSIONS

There is much to determine regarding the value of serological testing in COVID-19 diagnosis and monitoring. More comprehensive evaluations of their performance are rapidly underway. The use of serology methods requires appropriate interpretations of the results and understanding the strengths and limitations of such tests.

Accuracy of serological tests for diagnosis of chronic pulmonary aspergillosis: A systematic review and meta-analysis

Chronic pulmonary aspergillosis (CPA) is a slow and progressive disease that develops in preexisting lung cavities of patients with tuberculosis sequelae, and it is associated with a high mortality rate. Serological tests such as double agar gel immunodiffusion test (DID) or counterimmunoelectrophoresis (CIE) test have been routinely used for CPA diagnosis in the absence of positive cultures. However, these tests have been replaced with enzyme-linked immunoassay (ELISA) and, a variety of methods. This systematic review compares ELISA accuracy to reference test (DID and/or CIE) accuracy in CPA diagnosis. It was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The study was registered in PROSPERO under the registration number CRD42016046057. We searched the electronic databases MEDLINE (PubMed), EMBASE (Elsevier), LILACS (VHL), Cochrane library, and ISI Web of Science. Gray literature was researched using Google Scholar and conference abstracts. We included articles with patients or serum samples from patients with CPA who underwent two serological tests: ELISA (index test) and IDD and/or CIE (reference test). We used the test accuracy as a result. Original articles were considered without a restriction of date or language. The pooled sensitivity, specificity, and summary receiver operating characteristic curves were estimated. We included 14 studies in the review, but only four were included in the meta-analysis. The pooled sensitivities and specificities were 0.93 and 0.97 for the ELISA test. These values were 0.64 and 0.99 for the reference test (DID and/or CIE). Analyses of summary receiver operating characteristic curves yielded 0.99 for ELISA and 0.99 for the reference test (DID and/or CIE). Our meta-analysis suggests that the diagnostic accuracy of ELISA is greater than the reference tests (DID and/or CIE) for early CPA detection.

Proposal of Efficient Workflows for Confirmatory Neutralization Test for Initial Hepatitis B Surface Antigen Positive Samples

BACKGROUND

Since more sensitive immunoassays have been introduced, false positive Hepatitis B surface antigen (HBsAg) results are increasing. This study was carried out to propose a process to reduce the burden of the laboratory while increasing positive predictive value in HBsAg.

METHODS

Samples with Elecsys HBsAg II (Roche Diagnostics, Germany) between cutoff index (COI) 0.9 and 10.0 were tested with Elecsys HBsAg Confirmatory Test (Roche Diagnostics). If the COI value after neutralization is less than or equal to 60% of the COI treated with control reagent, the sample was determined as HBsAg positive.

RESULTS

A total of 133 samples were analyzed and 70.7% were confirmed positive. The highest COI of negatively confirmed sample was 5.6. Receiver operating characteristic curve analysis of HBsAg assay showed an area under curve of 0.761. Specificity was 100% at COI 6.0.

CONCLUSIONS

Based on this finding, the authors propose that only samples with HBsAg COI less than 6.0 need confirmatory tests.

Performance of 2 Commercial Serologic Tests for Diagnosing Zika Virus Infection

Reliable serologic tests are needed for diagnosis and surveillance of Zika virus infection. We evaluated the Euroimmun and Dia.Pro serologic tests for detection of Zika virus IgM and IgG by using a panel of 199 samples from a region endemic for flaviviruses. Kinetics of Zika virus antibodies were monitored from 300 sequential specimens sampled over a period of 10 months after infection. We observed suboptimal performance; sensitivity for Zika virus IgM was low, especially in the Euroimmun assay (49%), whereas IgM could be detected for months with the Dia.pro assay. The specificity of the Zika virus IgG assays was also low, especially that of Dia.Pro (62%); findings were strongly influenced by the epidemiologic context. These results highlight the complexity of serologic diagnosis of Zika virus infection in regions endemic for flaviviruses. Accurate analysis of the performance of assays is required to adapt and interpret algorithms.

Comparison of real world and core laboratory lupus anticoagulant results from the Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking (APS ACTION) clinical database and repository

BACKGROUND

Variability remains a challenge in lupus anticoagulant (LA) testing.

OBJECTIVE

To validate LA test performance between Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking (APS ACTION) Core laboratories and examine agreement in LA status between Core and local/hospital laboratories contributing patients to this prospective registry.

METHODS

Five Core laboratories used the same reagents, analyzer type, protocols, and characterized samples for LA validation. Non-anticoagulated registry samples were retested at the corresponding regional Core laboratories and anticoagulated samples at a single Core laboratory. Categorical agreement and discrepancies in LA status between Core and local/hospital laboratories were analyzed.

RESULTS

Clotting times for the reference/characterized plasmas used for normalized ratios were similar between Core laboratories (CV <4%); precision and agreement for LA positive/negative plasma were similar (all CV ≤5%) in the four laboratories that completed both parts of the validation exercise; 418 registry samples underwent LA testing. Agreement for LA positive/negative status between Core and local/hospital laboratories was observed in 87% (115/132) non-anticoagulated and 77% (183/237) anticoagulated samples. However, 28.7% (120/418) of samples showed discordance between the Core and local/hospital laboratories or equivocal LA results. Some of the results of the local/hospital laboratories might have been unreliable in 24.7% (41/166) and 23% (58/252) of the total non-anticoagulated and anticoagulated samples, respectively. Equivocal results by the Core laboratory might have also contributed to discordance.

CONCLUSIONS

Laboratories can achieve good agreement in LA performance by use of the same reagents, analyzer type, and protocols. The standardized Core laboratory results underpin accurate interpretation of APS ACTION clinical data.

Heparin-induced thrombocytopenia: An international assessment of the quality of laboratory testing

BACKGROUND

Accurate diagnosis of heparin-induced thrombocytopenia (HIT) is essential to ensure timely treatment and prevent complications. Current diagnostic assays include enzyme-linked immunosorbent assays (ELISAs) and rapid immunoassays (RIs). RIs offer fast turnaround times but were not significantly represented in previous external proficiency testing challenges.

OBJECTIVES

To use external proficiency testing to assess qualitative concordance for heparin/PF4 antibody detection.

METHODS

From 2013 to 2017, the External Quality Control for Assays and Tests (ECAT) Foundation distributed 10 samples internationally.

RESULTS

In total, 437 laboratories submitted 3149 results. ELISAs accounted for 1484 (47%) responses with RIs accounting for 1665 (53%) responses. RI use increased over the 5-year period. ELISAs classified 96% of both consensus positive and consensus negative samples concordantly. The coefficient of variation (CV) for positive sample optical densities (ODs) ranged from 35% to 50% when combining ELISA assay methods together. Quantitative RIs classified 97% of consensus-positive and 98% of consensus-negative samples concordantly. Qualitative RIs had a higher proportion of discordant responses and classified 88% of consensus-positive samples and 73% of consensus-negative samples concordantly. Of RIs only latex immunoassays and IgG specific chemiluminescent assays identified > 95% of samples concordantly with consensus.

CONCLUSION

Quantitative RIs and ELISAs classify > 95% of samples concordantly. The ODs from different ELISA methods vary considerably and are not interchangeable. Qualitative RI use is increasing despite a greater proportion of discordant classifications. This includes a higher than expected number of negative classifications for consensus-positive samples among many RIs, challenging their use as "rule out" tests.

Multilaboratory Assessment of Epstein-Barr Virus Serologic Assays: the Case for Standardization

IgA antibodies targeting Epstein-Barr virus (EBV) have been proposed for screening for nasopharyngeal carcinoma (NPC). However, methods differ, and the antigens used in these assays differ considerably between laboratories. To enable formal comparisons across a range of established EBV serology assays, we created a panel of 66 pooled serum samples and 66 pooled plasma samples generated from individuals with a broad range of IgA antibody levels. Aliquots from these panels were distributed to six laboratories and were tested by 26 assays measuring antibodies against VCA, EBNA1, EA-EBNA1, Zta, or EAd antigens. We estimated the correlation between assay pairs using Spearman coefficients (continuous measures) and percentages of agreement (positive versus negative, using predefined positivity cutoffs by each assay developer/manufacturer). While strong correlations were observed between some assays, considerable differences were also noted, even for assays that targeted the same protein. For VCA-IgA assays in serum, two distinct clusters were identified, with a median Spearman coefficient of 0.41 (range, 0.20 to 0.66) across these two clusters. EBNA1-IgA assays in serum grouped into a single cluster with a median Spearman coefficient of 0.79 (range, 0.71 to 0.89). Percentages of agreement differed broadly for both VCA-IgA (12% to 98%) and EBNA1-IgA (29% to 95%) assays in serum. Moderate-to-strong correlations were observed across assays in serum that targeted other proteins (correlations ranged from 0.44 to 0.76). Similar results were noted for plasma. We conclude that standardization of EBV serology assays is needed to allow for comparability of results obtained in different translational research studies across laboratories and populations.

Early detection and differential serodiagnosis of Mycoplasma hyorhinis and Mycoplasma hyosynoviae infections under experimental conditions

Mycoplasma hyorhinis (MHR) and Mycoplasma hyosynoviae (MHS) are common opportunistic pathogens in the upper respiratory tract and tonsils of swine. The identification of the specific species involved in clinical cases using conventional diagnostic methods is challenging. Therefore, a recombinant chimeric polypeptide based on the seven known variable lipoproteins (A-G) specific of MHR and a cocktail of surface proteins detergent-extracted from MHS cultures were generated and their suitability as antemortem biomarkers for serodiagnosis of MHR- and MHS-infection were evaluated by ELISA. M. hyorhinis and MHS ELISA performance, evaluated using serum samples collected over a 56-day observation period from pigs inoculated with MHR, MHS, M. hyopneumoniae, M. flocculare, or Friis medium, varied by assay, targeted antibody isotype, and cutoffs. The progressions of MHR and MHS clinical diseases were evaluated in relation to the kinetics of the isotype-specific antibody response in serum and bacterial shedding in oral fluids during the observation period. In pigs inoculated with MHR, bacterial DNA was detected in one or more of the 5 pens at all sampling points throughout the study, IgA was first detected at DPI 7, one week before the first clinical signs, with both IgA and IgG detected in all samples collected after DPI 14. The peak of MHS shedding (DPI 8) coincided with the onset of the clinical signs, with both IgA and IgG detected in all serum samples collected ≥ DPI 14. This study demonstrated, under experimental conditions, that both ELISAs were suitable for early detection of specific antibodies against MHR or MHS. The diagnostic performance of the MHR and MHS ELISAs varied depending on the selected cutoff and the antibody isotype evaluated. The high diagnostic and analytical specificity of the ELISAs was particularly remarkable. This study also provides insights into the infection dynamics of MHR-associated disease and MHS-associated arthritis not previously described.

Reassessment of hepatitis B virus window periods for two transcription-mediated amplification assays using screening data of South African blood donors

BACKGROUND

Transcription-mediated amplification assays for HBV DNA detection have transitioned from the Ultrio to the Ultrio Plus assay, which features increased analytic sensitivity due to inclusion of a target enhancer reagent. The impact on HBV detection for different categories of HBV infection has not been fully evaluated.

STUDY DESIGN AND METHODS

Hepatitis B virus (HBV) DNA and hepatitis B surface antigen (HBsAg) detection rates as well as viral load (VL) distributions in HBV nucleic acid test (NAT)-yield samples were compared during 1 year of screening of South African blood donors with the Ultrio assay and the subsequent year by the Ultrio Plus version. HBV-DNA concentration at the HBsAg seroconversion point was established by regression analysis using a set of antibody to hepatitis B core antigen-negative acute viremic samples.

RESULTS

Ultrio Plus detected twofold more window-period (WP) NAT yield donations and 1.7-fold more occult HBV infections than Ultrio. The VL distribution data indicated that Ultrio not only missed samples of less than 100 copies/mL, but also a substantial number higher than this level. The VL at the HBsAg seroconversion point was estimated at 916 copies/mL, whereas the VL at the NAT-conversion points was calculated at 63 and 4.1 copies/mL for Ultrio and Ultrio Plus. This reduced the infectious WP (compared to HBsAg testing) by 10.3 and 20.4 days, respectively.

CONCLUSION

The higher-than-expected increase in HBV-NAT yields after introduction of the Ultrio Plus assay is likely attributable to variable sensitivity of the former Ultrio assay for different HBV samples. Therefore, previously published HBV WP reduction and residual risk estimates based on analytical sensitivity of the Ultrio assay need to be revised.

Evaluation of serological testing for Lyme disease in Military Health System beneficiaries in Germany, 2013-2017

Lyme disease diagnostic workups conducted on active and retired U.S. service members and their dependents at U.S. Air Force military treatment facilities (MTFs) in Germany between 2013 and 2017 were assessed to determine the appropriateness of laboratory testing and antibiotic prescriptions. Of the 1,176 first-tier immunoassays, 1,114 (94.7%) were negative, and of the 285 immunoglobulin M (IgM) immunoblots, 242 (84.9%) followed a negative first-tier assay or were performed without an antecedent first-tier assay. Eighty-three positive IgM immunoblot tests were adjudicated using modified published criteria, of which 40 (48.2%) were deemed false positives. Thirtytwo patients with false-positive tests were treated with an antibiotic. Additionally, 30 patients with uncomplicated erythema migrans could have been treated without laboratory confirmation. Understanding the use and limitations of 2-tier diagnostic criteria, as well as the common pitfalls in diagnosing Lyme disease, may help prevent overdiagnosis, reduce unnecessary testing, and promote antibiotic stewardship.

Evaluation of the sensitivity and specificity of a novel line immunoassay for the detection of criteria and non-criteria antiphospholipid antibodies in comparison to established ELISAs

Background

Persistent antiphospholipid antibodies (aPL) constitute the serological hallmark of the antiphospholipid syndrome (APS). Recently, various new assay technologies for the detection of aPL better suited to multiplex reaction environments than ELISAs emerged. We evaluated the diagnostic performance of such a novel line immunoassay (LIA) for the simultaneous detection of 10 different aPL.

Methods

Fifty-three APS patients and 34 healthy controls were investigated for criteria (antibodies against cardiolipin [aCL], β2-glycoprotein I [aβ2-GPI]) and non-criteria aPL (antibodies against phosphatidic acid [aPA], phosphatidyl-choline [aPC], -ethanolamine [aPE], -glycerol [aPG], -inositol [aPI], -serine [aPS], annexin V [aAnnV], prothrombin [aPT]) IgG and IgM by LIA. Criteria aPL were additionally determined with the established Alegria (ALE), AcuStar (ACU), UniCap (UNI), and AESKULISA (AES) systems and non-criteria aPL with the AES system. Diagnostic performance was evaluated with a gold standard for criteria aPL derived from the results of the four established assays via latent class analysis and with the clinical diagnosis as gold standard for non-criteria aPL.

Results

Assay performance of the LIA for criteria aPL was comparable to that of ALE, ACU, UNI, and AES. For non-criteria aPL, sensitivities of the LIA for aPA-, aPI-, aPS-IgG and aPA-IgM were significantly higher and for aPC-, aPE-, aAnnV-IgG and aPC- and aPE-IgM significantly lower than AES. Specificities did not differ significantly.

Conclusions

The LIA constitutes a valuable diagnostic tool for aPL profiling. It offers increased sensitivity for the detection of aPL against anionic phospholipids. In contrast, ELISAs exhibit strengths for the sensitive detection of aPL against neutral phospholipids.

Performance of serological tests available in Brazil for the diagnosis of human visceral leishmaniasis

Background

Visceral leishmaniasis (VL) is the most severe form of leishmaniasis and is potentially fatal if not diagnosed and treated. Accurate and timely diagnosis is considered one of the pillars needed for the reduction in disease-related lethality. Brazil is currently one of the three eco-epidemiological hotspots for this disease. Several serological tests are commercially available in this country for VL diagnosis, although information on the performance of these tests is fragmented and insufficient. The aim of this study was to directly compare the performance of six commercial kits: three enzyme-linked immunosorbent assays (ELISAs), two immunofluorescence antibody tests (IFATs), one immunochromatographic test (ICT), besides one ICT, currently not commercially available in Brazil and one in-house direct agglutination test (DAT-LPC), not yet marketed.

Methodology/Principal findings

A panel of 236 stored samples from patients with clinically suspected VL, including 77 HIV-infected patients, was tested. IT-LEISH and DAT-LPC showed the highest accuracy rate among the non-HIV-infected patients, 96.2% [CI95%: 92.8–99.7%] and 95.6% [CI95%: 91.9–99.3%], respectively. For the ELISA tests evaluated, the maximum accuracy was 91.2%, and in the inter HIV-status group analysis, no significant differences were observed. For both IFATs evaluated, the maximum accuracy was 84.3%, and a lower accuracy rate was observed among the HIV-infected patients (p = 0.039) than among the non-HIV-infected patients. The DAT-LPC was the most accurate test in the HIV-infected patients (p≤0.115). In general, no significant difference in accuracy was observed among the VL-suspected patients stratified by age.

Conclusions/Significance

In summary, the differences in the performance of the tests available for VL in Brazil confirm the need for local studies before defining the diagnostic strategy.

Visceral leishmaniasis (VL) is a tropical disease distributed worldwide. In the Americas, Brazil reports about 96% of VL cases, which has been highlighted by the increase in lethality in last years. Accurate VL diagnosis is of utmost importance. Despite this, the performance of some commercial tests currently available in Brazil is unknown, especially for HIV-infected patients. Accordingly, in this study we present a comparative performance analysis of six commercial kits available in Brazil for the diagnosis of VL in non-HIV and HIV-infected patients, besides one immunochromatographic test (ICT) and one in-house direct agglutination test (DAT-LPC) currently not commercially available in Brazil. ICTs and DAT-LPC showed better performance among non-HIV infected patients. Despite the known limitation of serological tests for the diagnosis of patients with HIV, the direct agglutination test was more accurate in this specific group of patients. Our results demonstrate significant differences in the performance of different serological tests and confirm that the use of serology should be qualified with previous information on the performance of the tests.

Diagnostic Performance of Dengue Virus Envelope Domain III in Acute Dengue Infection

Dengue, one of the most prevalent illnesses caused by dengue viruses that are members of the genus Flavivirus, is a significant global health problem. However, similar clinical symptoms and high antigenic homologies with other Flaviviruses in the endemic area pose difficulties for differential diagnosis of dengue from other arbovirus infections. Here, we investigated four types of recombinant envelope protein domain III (DV-rED III) derived from four dengue virus (DENV) serotypes for diagnostic potential in detecting IgM in acute phase (mainly 2–3 days after onset of fever). Each independent DV-1, -3, and -4-rED III-ELISA showed less than 60% sensitivity, but the combined results of DV-1, -3, and -4-rED III-ELISA led to sensitivity of 81.82% (18/22) (95% CI, 59.72 to 94.81) and 100% specificity (46/46) (95% CI, 92.29 to 100.00) as each antigen compensated the other antigen-derived negative result. In conclusion, the independent combination of data derived from each recombinant antigen (DV1-, DV3-, and DV4-rED III) showed comparable efficacy for the detection of IgM in patients with acute-phase dengue infection.

Rapid fluorescent focus inhibition test optimization and validation: Improved detection of neutralizing antibodies to rabies virus

The rabies rapid fluorescent focus inhibition test (RFFIT) is the most widely used cell-based assay for detecting and quantitating rabies virus neutralizing antibodies (RVNA) in human serum. However, it is a complex, labor intensive, and somewhat subjective manual assay, the performance of which may be affected by a number of factors including the quality of cells and virus, variability of assay reagents and the skill and expertise of analysts. This study sought to identify and evaluate conditions that may impact RFFIT performance and RVNA detection by evaluating assay parameters including: different serial dilution scheme of serum samples in a 96-well microplate using semi-automated pipetting systems, the range of dose of challenge virus standard (CVS-11) strain of rabies virus, the effect of complement (C'), the effect of cell seeding density and passage number, the effect of diethylaminoethyl (DEAE) dextran concentration on virus infectivity, and the assay incubation period prior to immunostaining. In addition the evaluation of counting fluorescent foci using a microscope versus using scanned images from a cell imaging reader was performed in an effort to ease the reading of slides and have permanent records of the raw data. The results from optimization of each parameter are presented along with subsequent assay validation in accordance with the International Conference on Harmonization (ICH) guidelines. The improved and optimized RFFIT accuracy, linearity and sensitivity was demonstrated by testing World Health Organization (WHO)-1 and WHO-2 Standard Rabies Immune Globulins (SRIGs) and complete assay development and validation was performed in compliance with Good Clinical Laboratory Practice (GCLP) guidelines.

Magnitude of delayed turnaround time of laboratory results in Amhara Public Health Institute, Bahir Dar, Ethiopia

BACKGROUND

Clinical decisions depend on timely laboratory result reporting. The timeliness is commonly expressed in turnaround time and serves as a quality improvement tool to assess the effectiveness and efficiency of the laboratory. According to the International Organization for Standardization (ISO) guidelines, each laboratory shall establish turnaround times for each of its examinations that reflect clinical needs, and shall periodically evaluate whether or not it is meeting the established turnaround times. Therefore, this study aimed to assess the TAT of laboratory results done in the reference laboratories of the Amhara Public Health Institute, Bahir Dar, Ethiopia.

METHODS

A retrospective cross sectional study was carried out from 01 January to 31 September 2018. Each patient sample was considered as a study unit. Nine months data were extracted from the sample tracking log and from the Laboratory Information System (LIS) database. Descriptive and summary statistics were calculated using SPSS version 20.0 statistical software.

RESULTS

A total of 34,233 patients samples were tested during the study period. Monthly average TAT ranged from 38.6 to 51.3 days for tuberculosis (TB) culture, 5.3 to 42.4 days for exposed infant diagnosis (EID) for HIV, 8.4 to 26 days for HIV 1 viral load, and 1.9 to 3.5 days for TB genexpert tests. Compared with the standard, 76.5% of the viral load, 68.1% of the EID for HIV and 53.8% of the TB genexpert tests had delayed TAT. Repeated reagent stock out, high workload, activities overlapping, and staff turnover were major reasons for the result delays.

CONCLUSIONS

There was a delayed turnaround time of laboratory results in APHI. HIV viral load, EID and TB genexpert results were the most affected tests. Workload reduction plan, proper stock management, specific work assignment and trained staff retention are important approaches to minimize the delayed TAT in the setting.

Validation of the Limiting Antigen Avidity Assay to Estimate Level and Trends in HIV Incidence in an A/D Epidemic in Rakai, Uganda

The limiting-antigen avidity (LAg-Avidity) assay with viral load (VL) >1,000 copies/mL is being used to estimate population-level HIV incidence in Africa. However, this has not been validated in East Africa where HIV-1 subtypes A and D circulate. Sera from persons seen in two surveys (2008-2009 and 2012-2013) limited to those who attended the previous round of the Rakai Community Cohort in Uganda were analyzed. The performance of the current LAg-Avidity protocol, with a mean duration of recent infection (MDRI) of 130 days and false recent rate (FRR) of 0%, was compared with subtype-specific MDRI and FRR, adjusted to subtype distributions. The observed incidence was 1.05/100 person years (py) [95% confidence interval (CI) 0.90-1.23] in 2008-2009 and 0.66/100 py (95% CI 0.52-0.83) in 2012-2013. In contrast, the per-protocol LAg-Avidity incidence estimates were 1.63/100 py (95% CI 0.97-2.30) in 2008-2009 and 2.55/100 py (95% CI 1.51-3.59) in 2012-2013 (a significant increase, p < .05.) However, using a subtype-specific MDRI and FRR, the subtype adjusted incidence was 0.88% (95% CI 0.44-1.33) in 2008-2009 and 0.67% (95% CI 0.00-1.68) in 2012-2013, approximating to the observed incidence trends. In this subtype A/D epidemic, the per protocol LAg-Avidity + VL assay overestimated HIV incidence and failed to detect declines in incidence. Adjustment for FRR, MDRI, and subtype distribution provided incidence estimates similar to empirically observed incidence level and trends. Thus, use of the LAg-Avidity assay in an A/D epidemic requires adjustment for subtype.

Suboptimal Handling of Piccolo Samples or Reagent Discs for Consideration in Ebola Response

Operating clinical analyzers within recommended parameters can be challenging during outbreak response. Using the Piccolo Xpress point-of-care blood chemistry analyzer on guinea pig blood, we found that values of many analytes are still readily comparable when samples and reagent discs are handled at various conditions outside of manufacturer recommendations.