SARS-CoV-2 seroprevalence in Delhi, India: September October 2021: a population based seroepidemiological study

Background We conducted a repeat serosurvey in Delhi, India to estimate the seroprevalence of SARS-CoV-2 in the general population and compare the antibody prevalence in the vaccinated and non-vaccinated groups. Methods This cross sectional study was conducted from September 24 to October 14 2021 in 280 wards of Delhi among 27811 participants selected through a multistage sampling technique with housing settlement based stratification. The SARS-CoV-2 immunoglobulin (IgG) antibodies were screened with the VITROS (Ortho Clinical Diagnostics, Raritan, NJ, USA) assay (90% sensitivity, 100% specificity). Results A total of 24895 (89.5%) samples were seropositive. The crude seroprevalence was 87.99% (95% CI 89.1, 89.8), weighted for age and sex was 88% (95% CI 87.6, 88.4), and after adjustment of assay performance was estimated as 97.5% (95% CI 97.0, 98.0). The weighted seroprevalence in the 11 districts ranged from 84.9% (South-West district) to 90.8% (East district) Females in all the age-groups (<18, 18-49 and ≥50) had significantly higher odds of seropositivity (p<0.001). On adjusted analysis, the odds of seroconversion in the participants vaccinated with at-least one dose of either Covid-19 vaccine (Covishield/Covaxin) was more than four times compared to the unvaccinated (aRR 4.2 (3.8, 4.6)). The seroprevalence was also comparable among the complete and partially vaccinated subgroups for both vaccines (Table 4). Most (86.8%) seropositive individuals had a SARS-CoV-2 signal/cut-off ≥4.0 except in children Conclusions We observed IgG antibodies against SARS-CoV-2 in most of the general population of Delhi with likely higher antibody titers in the vaccinated compared to the unvaccinated groups.

EXPRESS: Repeat measurements on patient samples identifies unpredictable and poorly reproducible cardiac troponin results with a high-sensitivity cardiac troponin assay

There is much current interest in the use of low-normal high-sensitivity cardiac troponin (hsTn) concentrations, with or without minimal change, to rule out myocardial infarction (MI). Clifford-Mobley’s observations demonstrate that this a challenge even for platforms measuring hsTnT.1 Analytical imprecision may also affect algorithms that use hsTn change alone to rule in MI. For example, the imprecision observed with the Ortho hsTnI assay (Ortho Clinical Diagnostics, New Jersey, United States), using quality control or patient pools, has been found to exceed the European Society of Cardiology 0/1h algorithm criterion.2 The Ortho hsTnI assay has also been shown to yield high and non-reproducible results (i.e., outliers), in addition to the problems with imprecision.3 Outliers are often identified by repeat centrifugation and repeat testing. However, Ortho hsTnI results above the 99th percentile cutoffs may be discordant with respect to other cardiac troponin assays and the clinical diagnosis, even when imprecision from duplicate analysis is acceptable.4 As part of a stability study assessing Ortho hsTnI concentrations in both EDTA plasma and lithium heparin plasma over 24h, we have observed that this interference is random and not related to time on cells.

Increase in SARS-CoV-2 seroprevalence in healthy blood donors after the second wave of COVID-19 pandemic in South-Eastern Italy: evidence for asymptomatic young individuals as potential virus spreaders

Background: Italy has been the first among western countries to experience SARS-CoV-2 spread during which the southern regions were also heavily affected by the pandemic. To understand and monitor properly the evolution of COVID-19 pandemic, population based seroprevalence studies are a valid tool for the infection rates and effective prevalence of the SARS-CoV-2. Aim: In this prospective study, we assessed the changes in SARS-CoV-2 seroprevalence rates among non-vaccinated blood donors in South-Eastern Italy over May 2020 to March 2021. Methods: 8,183 healthy blood donors referring to the Transfusion Center at the University Hospital Riuniti of Foggia (Italy) for blood donation in the period May 2020-March 2021 were tested for anti-SARS-CoV-2 antibodies by Ortho Clinical Diagnostics VITROS 3600. None of the considered subjects had a diagnosed symptomatic COVID-19 infection. Results: Overall, 516 resulted positive for anti-SARS-CoV-2 IgG antibodies (6.3%, 95% CI, 0.03-0.15%), 387 (4.7%) were male and 129 (1.7%) female. A statistically significant increase in the seropositive population was found from May 2020 to March 2021 (Fisher's p<0.001). The difference of the seroprevalence was significant in terms of age but not sex (2-sided p<0.05 for age; 2-sided p>0.05 for sex) in both groups. Conclusion: Our study shows a significant increase in the SARS-CoV-2 seroprevalence among blood donors and suggests a potential role of asymptomatic individuals in continuing the spread of the pandemic. These results may contribute to establishing containment measures and priorities in vaccine campaigns.

Performance Evaluation: Four Chemiluminescent SARS-Cov-2 Immunoassays and Rapid-Card Test in Mild Disease and Seroprevalence of SARS CoV-2 in Frontline Healthcare Workers

Introduction: The COVID-19 pandemic raised a host of challenges to modern medicine. Key amongst these were in diagnostics, as most SARS-CoV-2 assays had been rapidly developed and released under emergency-use authorization with limited validation on clinical samples and secondly, an increased risk of COVID-19 infection to healthcare workers (HCW). There are limited inter-assay comparisons to detect SARS-CoV-2 antibodies in cases with milder symptoms of COVID-19, necessary to evaluate whether assays can detect SARS-CoV-2 antibodies in patients with mild infection. Aim: Therefore this study aimed to evaluate the performance of four chemiluminescence immunoassays and a rapid immunochromatographic assay in 100 rRT-PCR diagnosed-recovered frontline HCW with milder COVID-19 disease and secondly to evaluate the seroprevalence of SARS-CoV-2 infection in the asymptomatic frontline HCW at a multispeciality hospital in Delhi, India. Study Design: Serum and plasma samples were obtained from 100 rRT-PCR diagnosed-recovered frontline HCWs with mild disease working across the hospital, and performance of four common chemiluminescence immunoassays evaluated. Also samples of 505 asymptomatic, frontline HCWs working in hospital, who had not developed or shown any symptoms of COVID-19 infection to date was collected and the seroprevalence of infection was evaluated. Place and Duration of the Study: A study was conducted at BLK Superspeciality Hospital, New Delhi from September to October 2020. Methods: Four chemiluminescence immunoassays [Abbott SARS-CoV-2 IgG (Nucleocapsid), Roche Elecsys® Anti-SARS-CoV-2 Total (Nucleocapsid), Ortho-Clinical Diagnostics: VITROS Anti-SARS-CoV-2 IgG (Spike) and Anti-SARS-CoV-2 Total (Spike)] and a rapid assay [Medsource Ozone Biomedicals] were evaluated in 100 rRT-PCR diagnosed-recovered frontline HCW with mild disease. Also, seroprevalence was studied in 505 asymptomatic, frontline HCW. Results: At manufacturers' thresholds, overall sensitivity for Abbott was 71%, Roche 96%, Ortho (both total and IgG(S) 99% and rapid card 56%. Seroprevalence in asymptomatic frontline HCW was found to be 17.6%, with positivity being higher in the HCW group not facing patients directly compared to direct patient caregivers (P = 0.0034). Conclusion: Assay performance depends on assay design (total IgM & IgG antibodies versus IgG alone), choice of antigen, and time of sample testing from the onset of disease. In our study, Ortho Vitros total-Ab; IgG (Spike), and Roche Elecsys total-Ab (Nucleocapsid) assays were found to have optimal sensitivity. A seroprevalence study in the frontline HCWs at our institute showed that seroprevalence was higher (17.6%) in HCWs in comparison to the community.

Distinct SARS-CoV-2 antibody reactivity patterns in coronavirus convalescent plasma revealed by a coronavirus antigen microarray

A coronavirus antigen microarray (COVAM) was constructed containing 11 SARS-CoV-2, 5 SARS-1, 5 MERS, and 12 seasonal coronavirus recombinant proteins. The array is designed to measure immunoglobulin isotype and subtype levels in serum or plasma samples against each of the individual antigens printed on the array. We probed the COVAM with COVID-19 convalescent plasma (CCP) collected from 99 donors who recovered from a PCR+ confirmed SARS-CoV-2 infection. The results were analyzed using two computational approaches, a generalized linear model (glm) and random forest (RF) prediction model, to classify individual specimens as either Reactive or non-reactive against the SARS-CoV-2 antigens. A training set of 88 pre-COVID-19 specimens (PreCoV) collected in August 2019 and102 positive specimens from SARS-CoV-2 PCR+ confirmed COVID-19 cases was used for these analyses. Results compared with an FDA emergency use authorized (EUA) SARS-CoV2 S1-based total Ig chemiluminescence immunoassay (Ortho Clinical Diagnostics VITROS Anti-SARS-CoV-2 Total, CoV2T) and with a SARS-CoV-2 S1-S2 spike-based pseudovirus micro neutralization assay (SARS-CoV-2 reporter viral particle neutralization titration (RVPNT) showed high concordance between the three assays. Three CCP specimens that were negative by the VITROS CoV2T immunoassay were also negative by both COVAM and the RVPNT assay. Concordance between VITROS CoV2T and COVAM was 96%, VITROS CoV2T and RVPNT 93%, and RVPNT and COVAM 91%. The discordances were all weakly reactive samples near the cutoff threshold of the VITROS CoV2T immunoassay. The multiplex COVAM allows CCP to be grouped according to antibody reactivity patterns against 11 SARS-CoV-2 antigens. Unsupervised K-means analysis, via the gap statistics, as well as hierarchical clustering analysis revealed three main clusters with distinct reactivity intensities and patterns. These patterns were not recapitulated by adjusting the VITROS CoV2T or RVPNT assay thresholds. Plasma classified by COVAM reactivity patterns offers potential to improve CCP therapeutic efficacy CoV2T alone. The use of a SARS-CoV-2 antigen array can qualify CCP for administration as a treatment for acute COVID-19, and interrogate vaccine immunogenicity and performance in preclinical, clinical studies, and routine vaccination to identify antibody responses predictive of protection from infection and disease.

Disagreement between Cardiac Troponin Tests Yielding a Higher Incidence of Myocardial Injury in the Emergency Setting

Differences in patient classification of myocardial injury between high-sensitivity cardiac troponin (hs-cTn) assays have largely been attributed to assay design and analytical sensitivity aspects. Our objective was to compare Ortho Clinical Diagnostics’ (OCD) hs-cTnI assay to OCD’s contemporary/conventional assay (cTnI ES) and another hs-cTnI assay (Abbott hs-cTnI) in samples obtained from different emergency departments (EDs). Two different sample types were evaluated (lithium heparin and ethylenediaminetetraacetic acid (EDTA) plasma) in a non-selected ED population (study 1, n = 469 samples) and in patients for which ED physicians ordered cardiac troponin testing (study 2, n = 1147 samples), from five different EDs. The incidence of injury in study 1 was higher with the OCD hs-cTnI assay (30.9%; 95% CI: 26.9 to 35.2) compared to that of the Abbott hs-cTnI (17.3%; 95% CI: 14.1 to 21.0) and the OCD cTnI ES (15.4%; 95% CI: 12.4 to 18.9) assays, with repeat testing identifying 4.8% (95% CI: 3.0 to 7.5) of the OCD hs-cTnI results with poor reproducibility. In study 2, 4.6% (95% CI: 3.5 to 6.0) of the results were not reported for the OCD hs-cTnI assay (i.e., poor reproducibility) with 12.7% (95%CI: 8.7 to 17.8) of the OCD hs-cTnI results positive for injury being negative for injury with the Abbott hs-cTnI assay. In summary, the OCD hs-cTnI assay yields higher rates of biochemical injury with a higher rate of poor reproducible results in different ED populations.

Acute Phase Response and Non-Reproducible Elevated Concentrations with a High-Sensitivity Cardiac Troponin I Assay

High-sensitivity cardiac troponin (hs-cTn) testing has enabled physicians to make earlier diagnostic and prognostic decisions in the hospital setting than previous cardiac troponin assays. Analytical improvements have permitted one to measure cardiac troponin precisely in the nanogram per litre (ng/L) range with hs-cTn assays which has resulted in fast 0/1-h and 0/2-h algorithms for ruling-in and ruling-out myocardial infarction. Although analytical interferences that affect the reporting of hs-cTn are uncommon, not all hs-cTn assays are designed the same nor have undergone the same clinical and analytical validations. Here, after investigating an initial case of discrepant hs-cTnI results, we report that patients with an acute phase response (e.g., patients with inflammatory or infectious illnesses) can yield high and non-reproducible results with the Ortho Clinical Diagnostics hs-cTnI assay. Compared to Abbott Diagnostics hs-cTnI, Ortho Clinical Diagnostics hs-cTnI assay misclassifies biochemical injury in approximately 10% of the population being assessed for myocardial injury with imprecise results in approximately half of this population (i.e., 5%). In conclusion, caution is warranted in interpreting Ortho Clinical Diagnostics hs-cTnI alone in patients being evaluated for myocardial injury, especially in patients whose primary presentation is related to an acute phase response and not an acute coronary syndrome symptom.

Evaluating the Performance of Four SARS-CoV-2 Commercial Chemiluminescence Immunoassays

Background: COVID-19 is a pandemic of serious global threat that forced test developers to flood the market with various diagnostic assays that have been independently validated. Objectives: This study aims at assessing the performance of four SARS-CoV-2 chemiluminescence immunoassays. Methodology: The present study included sera from 96 Polymerase Chain Reaction (PCR)–confirmed COVID-19 cases collected at 2 time periods (5-9 days and 9-14 days post symptom onset) during patient follow-up, and 30 control sera from COVID-19 PCR–negative individuals. All sera were tested for SARS-CoV-2 antibodies using four high-throughput commercially available chemiluminescence immunoassays: YHLO Biotech Co, Ltd China (IgM and IgG); Abbott, Abbott USA (IgG); Roche, Roche US (total: IgM, IgG, and IgA), and Ortho, Ortho Clinical Diagnostics, USA (total and individual IgG). Results: For the detection of total antibodies (IgM, IgG, and IgA), the highest sensitivities were for Ortho followed by Roche assays (91.6% and 84.3% in 5-9 days period, respectively) raised to 96.8% and 92.7% in 9-14 days respectively with significant difference P-value <0.00001. Ortho, Roche, and YHLO iFlash (IgM) assays had specificities of 100%, 100%, and 90.3% respectively. Roche (Total) and Ortho (Total) assays showed perfect categorical agreement (94.4% in 5-9 days, and 96.4% in 9-14 days). As for the detection of individual IgG antibodies, the Abbott assay had the highest sensitivity (91.6% in 5-9 days, and 93.7% in 9-14 days), followed by Ortho and YHLO iFlash assays (84.3%, and 83.3% in 5-9 days respectively) that increased to 89.5% and 88.5% in 9-14 days respectively. Ortho assay was the best in specificity (100%), followed by Abbott (98.8%) and YHLO iFlash (96.3%). YHLO iflash (IgG) and Ortho (IgG) showed perfect agreement (96.8%) in the 2 time frames. Conclusion: Ortho assay showed the best performance in detecting total antibodies with perfect match to Roche assay, while Abott assay was the best performing in detecting individual IgG with perfect match to Ortho assay rendering them to be efficient diagnostic tools

PREVALENCE OF IRREGULAR RED CELLANTIBODIES IN HEALTHY BLOOD DONORS ATTENDING A TERTIARY CARE HOSPITAL IN SOUTH INDIA

Introduction: Red cell antibodies that are found normally in human serum are considered naturally occurring and those are anti A and anti B. All other antibodies directed against RBC antigens are considered “unexpected or irregular". Aim: This study is aimed to evaluate the prevalence of the anti-red blood cell antibodies among healthy blood donors. Material and Methods: Antibody screening and identification was done using commercially available 3 cell and 11 cell reagent cells (0.8% Surgiscreen, Ortho Clinical Diagnostics Limited, USA and Low ionic Strength Saline Ortho Bliss with AHG Cassettes) in antihuman globulin phase. Results: A total of 36,684 donors were screened for the presence of irregular erythrocyte antibodies. Among these donors, twenty donors showed presence of alloantibodies in their serum (0.054%). Most frequent alloantibodies identified were from Lewis blood group system. The results showed statistically a higher prevalence of RBC alloantibodies in males than in females. Conclusion: Screening for presence of alloantibodies in donor blood is important to provide compatible blood products and to avoid transfusion reactions.

Declining antibody levels to Trypanosoma cruzi correlate with polymerase chain reaction positivity and electrocardiographic changes in a retrospective cohort of untreated Brazilian blood donors

Background Although infection with Trypanosoma cruzi is thought to be lifelong, less than half of those infected develop cardiomyopathy, suggesting greater parasite control or even clearance. Antibody levels appear to correlate with T. cruzi (antigen) load. We test the association between a downwards antibody trajectory, PCR positivity and ECG alterations in untreated individuals with Chagas disease. Methodology/Principal findings This is a retrospective cohort of T. cruzi seropositive blood donors. Paired blood samples (index donation and follow-up) were tested using the VITROS Immunodiagnostic Products Anti-T.cruzi (Chagas) assay (Ortho Clinical Diagnostics, Raritan NJ) and PCR performed on the follow-up sample. A 12-lead resting ECG was performed. Significant antibody decline was defined as a reduction of > 1 signal-to-cutoff (S/CO) unit on the VITROS assay. Follow-up S/CO of < 4 was defined as borderline/low. 276 untreated seropositive blood donors were included. The median (IQR) follow-up was 12.7 years (8.5–16.9). 56 (22.1%) subjects had a significant antibody decline and 35 (12.7%) had a low/borderline follow-up result. PCR positivity was lower in the falling (26.8% vs 52.8%, p = 0.001) and low/borderline (17.1% vs 51.9%, p < 0.001) antibody groups, as was the rate of ECG abnormalities. Falling and low/borderline antibody groups were predominantly composed of individuals with negative PCR and normal ECG findings: 64% and 71%, respectively. Conclusions/Significance Low and falling antibody levels define a phenotype of possible spontaneous parasite clearance.