Total Antibody Assay Research Articles

Longitudinal profile of neutralizing and binding antibodies in vaccinated and convalescent COVID-19 cohorts by chemiluminescent immunoassays.

IntroductionSurrogate rapid serological assay was urgently demanded for accessibly interpretation of immunity potency and duration of neutralizing antibody against SARS‐CoV‐2. The longitudinal trajectory of antibody profile with a reliable large‐scale assay was crucial to judge the protective immune status, avoid futile therapy and provide insight into the booster vaccination minimizing the risk of COVID‐19.MethodsA total of 195 volunteers were enrolled for a two‐doses procedure (0 and 28 days) of inactive vaccination, as well as ten COVID‐19 convalescents. The serum was collected at six time point and detected by chemiluminescent immunoassay with SARS‐CoV‐2 neutralizing antibody (Nab), SARS‐CoV‐2 RBD immunoglobulin G (IgG) antibody (RBD IgG) and RBD total antibody. The diagnostic results and the correlation of antibody level were evaluated among three serological (Nab, RBD IgG, and RBD total antibody) assay, as well as with an authorized cPass kit (Nab). Referred to the assay‐specific threshold, the seroconversion rate and dynamic titer of antibody were exhibited from 0 to 56 days since vaccination.ResultsThere was no difference observed with diagnostic results between neutralizing and RBD IgG antibody (p > 0.05). Both diagnostic results of neutralizing and RBD IgG antibody testing differentiated from RBD total antibody assay (p < 0.05). The coefficient of correlation (R) was above 0.90 among the levels of those three antibodies, more than 0.60 in comparison with neutralizing antibody by cPass enzyme‐linked immunoassay. The “S” varying pattern for various antibodies level was observed with time extension after vaccination. The seroconversion rate was below 11.1% in 2 weeks after the priming dose, while the value climbed to 81% in 1 week after the boosting dose. The seroconversion rate was maintained around 91%. The inactive vaccine elicited 81‐fold higher antibody levels after finished the vaccination schedule than that at the basic point. Besides, the level of neutralizing antibody induced by vaccine was found with a 0.2‐fold ratio by comparison with that in COVID‐19 convalescents.ConclusionThe humoral immune response products including SARS‐CoV‐2 neutralizing, RBD IgG antibody and total antibody and the varying pattern of the antibody profile could be rapidly detected by CILA method. Meanwhile, the continuing and dynamic determination was attributed to evaluate the protection effect of humoral immunity against the SARS‐CoV‐2 infection.

Clinical Performance of a Lateral Flow SARS-CoV-2 Total Antibody Assay.

BackgroundSerological assays for SARS-CoV-2 are important tools for diagnosis in patients with negative RT-PCR testing, pediatric patients with multisystem inflammatory syndrome, and serosurveillance studies. However, lateral flow-based serological assays have previously demonstrated poor analytical and clinical performance, limiting their utility.MethodsWe assessed the ADEXUSDx COVID-19 lateral flow assay for agreement with diagnostic RT-PCR testing using 120 specimens from RT-PCR–positive patients, 77 specimens from symptomatic RT-PCR–negative patients, and 47 specimens obtained prepandemic. Specimens collected <14 days from symptom onset in RT-PCR–positive patients were compared relative to the Abbott SARS-CoV-2 IgG assay.ResultsThe ADEXUSDx COVID-19 Test yielded an overall positive percent agreement (PPA) of 92.5% (95%CI 85.8 to 96.3) and negative percent agreement of 99.2% (95% CI 94.9–100.0) relative to RT-PCR and in prepandemic specimens. Relative to days from symptom onset, the PPA after 13 days was 100% (95% CI 94.2–100); from 7 to 13 days, 89.7 (95% CI 71.5–97.2); and from 0 to 7 days, 53.8 (95% CI 26.1–79.6). The overall agreement between the Abbott and ADEXUSDx assays was 80.9%. Twenty-five specimens were positive by both assays, 9 specimens were negative by both assays, and 8 specimens were positive by only the ADEXUSDx assay.ConclusionsWe demonstrate high PPA and negative percent agreement of the ADEXUSDx COVID-19 assay and diagnostic testing by RT-PCR, with PPA approximately 90% by 7 days following symptom onset. The use of waived testing for antibodies to SARS-CoV-2 with high sensitivity and specificity provide a further tool for combatting the COVID-19 pandemic.

Comparison of SARS-CoV-2 Antibodies and Six Immunoassays in Pediatric and Adult Patients 12 Weeks After COVID-19

IntroductionSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific humoral immune persistence has been proposed to be affected by patients’ characteristics. Moreover, available conflicting assay results are needed to be settled through comparative research with defined clinical specimens.MethodsThis prospective study investigated SARS-CoV-2-specific antibodies among 43 adults and 34 children at a mean of 12 weeks after the onset of COVID-19 symptoms using six serological assays and compared their performance. We used two Euroimmun (Euroimmun, Luebeck, Germany), two automated Roche Elecsys (Basel, Switzerland), and two rapid immuno-chromatographic Ecotest (Matrix Diagnostics, Assure Tech. (Hangzhou) Co., L, China) assays to investigate SARS-CoV-2 antibodies.ResultsThe findings showed that the Roche Elecsys anti-S total test yielded the best positivity/sensitivity (children 94.1% and adults 93.0%; p = 0.877) while five immunoglobulin IgG targeting assays had similar positivity/sensitivity between children (88.2% to 94.1%) and adults (88.4% to 93.0%) (p > 0.05). Although IgM positivity was relatively low (p < 0.001), it was found in the majority of our pediatric and adult patients (67.6% and 86.0%, respectively; p = 0.098). SARS-CoV-2 S IgG titers were found to be higher among males in pediatric and adult groups compared to females (p = 0.027 and p = 0.041, respectively). Furthermore, we observed significantly higher antibody titers among pneumonia patients (p = 0.001).ConclusionOverall, we concluded SARS-CoV-2 antibody persistence over an average of 12 weeks after the onset of COVID-19 symptoms. While automated Roche Elecsys total antibody assays yielded the best sensitivity (> 90%) and five assays targeting IgG had acceptable performance. Patients with pneumonia and males have higher antibody titers. The effect of antibody persistence on re-infections should be monitored in longitudinal studies.

Salivary antibodies are detected with a commercial anti-SARS-CoV-2 assay only after two doses of vaccine using serum thresholds

Salivary matrix is an appealing specimen type for SARS-CoV-2 serology because of ease of collection and potential for concurrent nucleic acid testing. We address the feasibility of salivary matrix to detect anti-SARS-CoV-2 antibodies using two commercially available anti-SARS-CoV-2 Total antibody assays including analytical validations.Matched serum and saliva samples were collected from 10 convalescent COVID-19 patients and tested using a quantitative anti-Spike Total antibody assay and a qualitative anti-Nucleocapsid Total antibody assay from Roche Diagnostics. Both assays were 100% sensitive for COVID-19 history in serum. However, saliva samples were below serum positivity thresholds. We then collected longitudinal salivary samples from a volunteer cohort receiving the Pfizer-BioNTech COVID-19 BNT162b2 vaccine. Saliva was negative for anti-SARS-CoV-2 antibodies at 5 time points after a single dose of vaccine including day 56 when mean (min-max) serum levels of anti-Spike Total antibody were 79.0 U/mL (46.6–110.1) (N = 8). After a second vaccine dose serum-matched samples were beyond the analytical measuring range of the assay (>2500 U/mL), and detection of salivary anti-Spike Total antibody was achieved in all volunteers (12.2 U/mL [2.0–32.7]) (N = 11) 30 days after the second dose. Mean anti-Spike Total antibody levels in serum (1558 U/mL (434–>2500)) and saliva (2.6 U/mL (<0.4–11.4)) declined 216–233 days after the first dose of vaccine (P < 0.05); and saliva was 75% sensitive for two doses of vaccination at this latter time point (N = 25). These data suggest commercial assays are capable of detecting vaccine status after two doses of BNT162b2 vaccine up to 6 months and could inform COVID-19 surveillance.

Long-Term Comparison of 7 SARS-CoV-2 Antibody Assays in the North Zealand Covid-19 Cohort.

BackgroundThroughout the coronavirus disease 2019 (Covid-19) pandemic numerous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody assays have been approved through Emergency Use Authorization and require further evaluation of sensitivity and specificity in clinical laboratory settings prior to implementation.MethodsWe included 1733 samples from 375 PCR-confirmed SARS-CoV-2–positive individuals of the North Zealand Covid-19 Cohort in an 8-month period. We investigated diagnostic sensitivity and specificity against consensus and PCR and interassay agreement over time for 5 SARS-CoV-2 immunoassays [Roche-nucleocapsid (NC)-total, Roche-receptor binding domain (RBD)-total, Siemens-RBD-IgG, Siemens-RBD-total, Thermo Fisher Scientific (TFS)-RBD-IgG] commercially available on automated platforms and 2 ELISA assays (TFS-RBD-total, Wantai-RBD-total).ResultsEarly interassay discrepancy in up to 49% of samples decreased steadily during the first 18 days. By day 18, all assays had reached a plateau between 82.3% and 90.5% seropositivity compared to PCR. Assays ranked by closest agreement with the consensus model beyond day 18 (sensitivity/specificity against consensus) were as follows: Roche-RBD-total, 99.8%/100.0%; Wantai-RBD-total, 99.8%/99.7%; Roche-NC-total, 97.8%/100.0%; Siemens-RBD-total, 98.0%/98.7%; TFS-RBD-total, 96.9%/99.7%; TFS-RBD-IgG, 91.5%/100.0%; and Siemens-RBD-IgG, 94.6%/89.9%. We found that 7.8% of PCR-positive patients remained seronegative in all assays throughout the study.ConclusionsAll included assays had sensitivities against consensus >90% past day 18. For the current recommended use of antibody assays to detect former, undocumented Covid-19, our data suggest the use of total antibody assays rather than IgG-specific assays due to higher long-term sensitivity. Finally, a nonresponding subpopulation of 7.8% in our cohort with persistent seronegative results raises concern of a possible substantial number of people with continued low protection following natural SARS-CoV-2 infection.

P342 Trans-continental analysis of over, 2000 Inflammatory Bowel Disease patients implicates geography, disease type, and exposure to immunosuppression as drivers of SARS-CoV-2 seroprevalence: data from the ICARUS-IBD Consortium

BackgroundIBD patients on immune-modulatory therapies are considered high-risk for SARS-CoV-2 infection. Direct comparisons of serological responses to SARS-CoV-2 infection in IBD patients across different continents and medications are lacking. We performed SARS-CoV-2 sero-surveillance of IBD patients prior to vaccination at seven large tertiary centres in Asia, Europe, and North America.MethodsClinical data and sera were collected from, 2,213 IBD patients receiving routine care at institutions in Belgium, Canada, Hong Kong, India, Japan, the United Kingdom, and the United States between, 26 May, 2020 and, 24 September, 2021 (Table, 1). Sera were taken prior to vaccination. Clinical data were collected through patient questionnaires and medical records. Antibody reactivity to the SARS-CoV-2 spike protein was assessed using the Roche SARS-CoV-2 anti-spike total antibody and/or Siemens Healthineers COV2T anti-spike total antibody assays, which showed, 99.4% concordance. Univariate analysis was performed to evaluate association between individual variables and sero-status.ResultsThe pre-vaccination seroprevalence of antibodies to SARS-CoV-2 in IBD patient varied widely according to location from, 0% in Hong Kong to, 57.9% in New Delhi, India (p<0.001). Rates in Europe and North America were similar (range, 3.57%-8.94%). Overall, SARS-CoV-2 seroprevalence appears to be equal to or less than local populations (Table, 2). Seroprevalence rates were associated with IBD type (7.8% CD, 12.4% UC, 15% IBD-U, p<0.001), smoking status (p<0.001), and history of COVID diagnosis (p<0.001) or COVID hospitalization (p=0.001), and any IMM (p<0.001). (Table, 3). Whilst there were no significant differences in seroprevalence between patients receiving infliximab (IFX), vedolizumab (VDZ), and ustekinumab (UST), antibody levels were attenuated in patients on IFX monotherapy and combination therapy (both p=0.002) and VDZ (p=0.02), compared with no medications (Figure 1). ConclusionWe confirm in diverse poulations that exposure to biologics or immunomodulators, type of disease, and smoking status are associated with seroprevalence and antibody levels. We show for the first time the dominant influence of geographical location on sero-status in these patients. These observations should be considered as we look towards post-vaccination data to help stratify patients for clinical guidelines on SARS-CoV-2 vaccination.

Heterologous SARS‐CoV‐2 vaccinations in patients with B‐cell lymphoid malignancies

Heterologous <scp>SARS‐CoV</scp>‐2 vaccinations in patients with B‐cell lymphoid malignancies

Estimation of SARS-CoV-2 Infection Fatality Rate by Age and Comorbidity Status Using Antibody Screening of Blood Donors During the COVID-19 Epidemic in Denmark.

BackgroundStudies presenting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection fatality rate (IFR) for healthy individuals are warranted. We estimate IFR by age and comorbidity status using data from a large serosurvey among Danish blood donors and nationwide data on coronavirus disease 2019 (COVID-19) mortality.MethodsDanish blood donors aged 17–69 years donating blood October 2020–February 2021 were tested with a commercial SARS-CoV-2 total antibody assay. IFR was estimated for weeks 11 to 42, 2020 and week 43, 2020 to week 6, 2021, representing the first 2 waves of COVID-19 epidemic in Denmark.ResultsIn total, 84944 blood donors were tested for antibodies. The seroprevalence was 2% in October 2020 and 7% in February 2021. Among 3898039 Danish residents aged 17–69 years, 249 deaths were recorded. The IFR was low for people <51 years without comorbidity during the 2 waves (combined IFR=3.36 per 100000 infections). The IFR was below 3‰ for people aged 61–69 years without comorbidity. IFR increased with age and comorbidity but declined from the first to second wave.ConclusionsIn this nationwide study, the IFR was very low among people <51 years without comorbidity.

Clinical Evaluation of Siemens SARS-CoV-2 Total Antibody assay and IgG assay using the Dimension EXL 200 in the Tokyo Metropolitan area

BackgroundWe evaluated the efficacy of the Siemens SARS-CoV-2 Total Antibody assay (CV2T) and IgG assay (CV2G) that can detect antibodies against the receptor binding domain of S antigen in patients with COVID-19 in a Tokyo metropolitan area. MethodsSensitivity and antibody levels were examined by CV2T and CV2G on Dimension EXL 200 using 236 serum samples obtained from 79 RT-PCR confirmed COVID-19 patients at multiple time points and were compared with disease severity by the World Health Organization criteria. The assay specificity was evaluated using samples collected before the COVID-19 pandemic. ResultsThe sensitivity of CV2T and CV2G were low (16.7–21.4%) in days 0–6 and increased to 43.8–52.5% in days 7–13 and to 80.8–90.0% in days 14–20. The seroprevalences persisted after day 21 to days past 42 regardless of disease severity. In every day grouping, mean antibody levels were higher in severe cases than in mild cases with a significant difference in days 14–20 and days 20–27. The specificity was 97.9 % (95% CI; 92.8–99.8) for CV2T and 99.0 % (95% CI; 94.6–100) for CV2G. ConclusionsOur results indicate a high specificity and high sensitivity at 14 days of CV2T and CV2G as antibody detection assays.

Waning of IgG, Total and Neutralizing Antibodies 6 Months Post-Vaccination with BNT162b2 in Healthcare Workers.

Data about the long-term duration of antibodies after SARS-CoV-2 vaccination are still scarce and are important to design vaccination strategies. In this study, 231 healthcare professionals received the two-dose regimen of BNT162b2. Of these, 158 were seronegative and 73 were seropositive at baseline. Samples were collected at several time points. The neutralizing antibodies (NAbs) and antibodies against the nucleocapsid and the spike protein of SARS-CoV-2 were measured. At day 180, a significant antibody decline was observed in seronegative (−55.4% with total antibody assay; −89.6% with IgG assay) and seropositive individuals (−74.8% with total antibody assay; −79.4% with IgG assay). The estimated half-life of IgG from the peak humoral response was 21 days (95% CI: 13–65) in seronegative and 53 days (95% CI: 40–79) in seropositive individuals. The estimated half-life of total antibodies was longer and ranged from 68 days (95% CI: 54–90) to 114 days (95% CI: 87–167) in seropositive and seronegative individuals, respectively. The decline of NAbs was more pronounced (−98.6%) and around 45% of the subjects tested were negative at day 180. Whether this decrease correlates with an equivalent drop in the clinical effectiveness against the virus would require appropriate clinical studies.

Evaluation of the Humoral Response to Adeno-Associated Virus-Based Gene Therapy Modalities Using Total Antibody Assays.

The number of viral vector-based gene therapies (GTx) continues to grow with two products (Zolgensma® and Luxturna®) approved in the USA as of March 2021. To date, the most commonly used vectors are adeno-associated virus-based (AAV). The pre-existing humoral immunity against AAV (anti-AAV antibodies) has been well described and is expected as a consequence of prior AAV exposure. Anti-AAV antibodies may present an immune barrier to successful AAV transduction and hence negatively impact clinical efficacy and may also result in adverse events (AEs) due to the formation of large immune complexes. Patients may be screened for the presence of anti-AAV antibodies, including neutralizing (NAb) and total binding antibodies (TAb) prior to treatment with the GTx. Recommendations for the development and validation of anti-AAV NAb detection methods have been presented elsewhere. This manuscript covers considerations related to anti-AAV TAb-detecting protocols, including the advantages of the use of TAb methods, selection of assay controls and reagents, and parameters critical to monitoring assay performance. This manuscript was authored by a group of scientists involved in GTx development representing eleven organizations. It is our intent to provide recommendations and guidance to industry sponsors, academic laboratories, and regulatory agencies working on AAV-based GTx viral vector modalities with the goal of achieving a more consistent approach to anti-AAV TAb assessment. Graphical abstract

Antibody Response Against SARS-CoV-2 Following ChAdOx1 (Astezeneca AZD 1222) Vaccine in Health Care Workers in a Tertiary Care Hospital in India

BACKGROUND: The ChAdOx1 nCoV-19 vaccine against COVID-19 is a two-dose vaccine spread 3 to 4 weeks apart. This study aims to ascertain the antibody response to each dose with respect to age, previous infection status etc. METHODS: Baseline total COVID-19 antibody level was ascertained using Siemens SARS‑CoV‑2 Total Antibody assay in consenting health care workers before the first dose of vaccination. Adverse effects were noted in each individual and were monitored weekly for the total antibody titre following both doses. Descriptive statistical tests were used to analyse the changes in antibodies levels weekly after both doses. Association of previous COVID infection and age with antibody levels was assessed. RESULTS: Median (range) of age of the 30 study participants was 31.5 years.23% of the participants had a history of previous COVID-19 infection. Mild adverse events following immunisation were reported by 87% participants after first dose whereas only in 7% after second dose. Median baseline antibody titres were significantly higher among those with previous COVID infection as compared to previously uninfected individuals. Antibody titres increased consistently after first dose and showed a declining trend following the second dose in all participants and showed no significant association with previous COVID-19 infection or age. CONCLUSIONS: Antibody titre response was similar amongst the various age groups. Higher response in the previously infected individuals following first dose may make them ideal candidates for a single dose vaccine regimen. Individuals showing lower levels of neutralising antibodies can be ideal candidates for a booster dose.

ESTIMATION OF SARS COV 2 SPECIFIC ANTIBODIES SEROPREVALENCE IN HEALTHCARE WORKERS IN DISTRICT UDAIPUR, INDIA

Background: Current pandemic caused by Novel coronavirus (COVID-19) causes clinical symptoms from fever to acute respiratory distress syndrome but may remain mild or asymptomatic. To evaluate the cumulative prevalence of SARS-CoV-2 infection in a community and know how immune response develops in the population, reliable assay alongwith RT-PCR for detection of SARS CoV 2 antibodies is needed. Healthcare workers (HCWs) represent a high-risk population for infection with SARS-CoV-2. Methods: We evaluated total antibodies recognizing the SARS CoV 2 receptor binding domain (S1-RBD) or the Spike protein over a period of six months in a total of 310 healthcare workers engaged in hospital using SARS-CoV-2 Total antibody assay kit. The overall Findings: seroprevalence found in our analysis was 41.93%. In case of males the percentage positive was found to be signicantly higher at 43.91%, compared to females at 36.25%. Seroprevalence was signicantly higher in 50 years above age group in comparison to 20-50 years old aged healthcare workers. The seroprevalence was higher in doctors, nursing staff and lab technicians than other healthcare professionals as 44.6%. Conclusions: This study showed high seroprevalence of SARS-CoV-2 in healthcare workers which means remaining proportion of the healthcare workers are still susceptible to the infection. Good compliance to infection eradication and control measures, adequate PPEs, and early detection and isolation of healthcare workers infected with SARS-CoV-2 are mandatory to reduce the risk of SARS-CoV-2 infection

Multiplex assessment of SARS-CoV-2 antibodies improves assay sensitivity and correlation with neutralizing antibodies

ObjectivesDetection of antibodies to multiple SARS-CoV-2 antigens in a single assay could increase diagnostic accuracy, differentiate vaccination from natural disease, and aid in retrospective exposure determination. Correlation of binding antibody assessment in clinical assays with neutralizing antibodies is needed to better understand the humoral response to SARS-CoV-2 infection and establish of correlates of protection. MethodsA cohort of 752 samples was used to assess specificity, sensitivity, and comparison to 6 other Conformitè Europëenne serologic assays for the BioRad SARS-CoV-2 IgG multiplex assay which measures receptor binding domain IgG (RBD), spike-S1 IgG (S1), spike-S2 IgG (S2), and nucleocapsid IgG (N). A subset of serial specimens from 14 patients was also tested for neutralizing antibodies (n = 61). ResultsSpecificity for RBD and S1 IgG was 99.4% (n = 170) and 100% for S2 and N IgG (n = 170) in a cohort selected for probable interference. Overall assay concordance with other assays was >93% for IgG and total antibody assays and reached 100% sensitivity for clinical concordance at >14 days as a multiplex assay. RBD and S1 binding antibody positivity demonstrated 79–95% agreement with the presence of neutralizing antibodies. ConclusionsThe BioRad SARS-CoV-2 IgG assay is comparable to existing assays, and achieved 100% sensitivity when all markers were included. The ability to measure antibodies against spike and nucleocapsid proteins simultaneously may be advantageous for complex clinical presentations, epidemiologic research, and in decisions regarding infection prevention strategies. Additional independent validations are needed to further determine binding antibody and neutralizing antibody correlations.

Clinical performance of the Elecsys® anti-SARS-CoV-2 combined in an algorithm with two specific anti-IgG immunoassays for the evaluation of the serological response of patients with COVID-19 in a population with a high prevalence of infection.

Anti-SARS-CoV-2 antibodies have been used in the study of the immune response in infected patients. However, differences in sensitivity and specificity have been reported, depending on the method of analysis. The aim of the present study was to evaluate the diagnostic accuracy of an algorithm in which a high-throughput automated assay for total antibodies was used for screening and two semi-automated IgG-specific methods were used to confirm the results, and also to correlate the analytical results with the clinical data and the time elapsed since infection. We studied 306 patients, some hospitalized and some outpatients, belonging to a population with a high prevalence of COVID-19. One-hundred and ten patients were classified as SARS-CoV-2 negative and 196 as positive by polymerase chain reaction. The algorithm and automated assay alone had a specificity and a positive predictive value of 100%, although the sensitivity and negative predictive value of the algorithm was higher. Both methods showed a good sensitivity from day 11 of the onset of symptoms in asymptomatic and symptomatic patients. The absorbance of the total antibodies was significantly higher in severely symptomatic than in asymptomatic or mildly symptomatic patients, which suggests the antibody level was higher. We found 15 patients who did not present seroconversion at 12 days from the onset of symptoms or the first polymerase chain reaction test. This study highlights the proper functioning of algorithms in the diagnosis of the immune response to COVID-19, which can help to define testing strategies against this disease.

ESTIMATION OF SARS-COV-2 SPECIFIC ANTIBODIES SEROPREVALENCE IN HEALTHCARE WORKERS IN DISTRICT UDAIPUR, INDIA

Background:Current pandemic caused by Novel coronavirus (COVID-19) causes clinical symptoms from fever to acute respiratory distress syndrome but may remain mild or asymptomatic. To evaluate the cumulative prevalence of SARSCoV-2 infection in a community and know how immune response develops in the population, reliable assay alongwith RT-PCR for detection of SARS-CoV 2 antibodies is needed. Healthcare workers (HCWs) represent a high-risk populat - ion for infection with SARS-CoV-2. Methods: We evaluated total antibodies recognizing the SARS CoV 2 receptor binding domain (S1-RBD) - - - or the Spike protein over a period of six months in a total of 310 healthcare workers engaged in hospital using SARS-CoV-2 Total antibody assay kit. Findings: The overall seroprevalence found in our analysis was 41.93%. In case of males the percentage positive was found to be signicantly higher at 43.91%, compared to females at 36.25%. Seroprevalence was signicantly higher in 50 years above age group in comparison to 20-50 years old aged healthcare workers. The seroprevalence was higher in doctors, nursing staff and lab technicians than other healthcare professionals as 44.6%. Conclusions: This study showed high seroprevalence of SARS-CoV-2 in healthcare workers which means remaining proportion of the healthcare workers are still susceptible to the infection. Good compliance to infection eradication and control measures, adequate PPEs, and early detection and isolation of healthcare workers infected with SARS-CoV-2 are mandatory to reduce the risk of SARS-CoV-2 infection.

SARS-CoV-2 PCR positivity rate and seroprevalence of related antibodies among a sample of patients in Cairo: Pre-wave 2 results of a screening program in a university hospital.

Research has revealed that asymptomatic and pre-symptomatic infections are important contributors to the transmission of SARS-CoV-2 in populations. In Egypt, the true prevalence of infections is veiled due to the low number of screening tests. The aim of this study was to determine the SARS-CoV-2 PCR positivity rate as well the seroprevalence of the SARS-CoV-2 antibodies before the ultimate development of a second wave of the epidemic in Cairo, Egypt. Our study was carried out between May 5 and the end of October 2020. It included all patients requiring admission to Ain Shams University hospitals. An interview questionnaire was used to collect demographic and clinical data. Laboratory tests for all participants included RT-PCR and total antibody assay for SARS-CoV-2. A total of 4,313 subjects were enrolled in our study, with females representing 56% of the sample. Adults and middle-aged individuals represented around 60% of the study sample. The positivity rate of SARS-CoV-2 PCR was 3.84% (95% CI 3.29-4.48), and the SARS-CoV-2 antibody seroprevalence was 29.82% (95% CI: 28.16-31.51). Males showed a higher risk for getting the COVID-19 infection, while middle-age group had significantly higher antibody seroprevalence rates. SARS-CoV-2 infection imposes a high burden on the community as detected by high seroprevalence rates.

A comparison of SARS-CoV-2 nucleocapsid and spike antibody detection using three commercially available automated immunoassays

IntroductionCommercially available serological assays for SARS-CoV-2 detect antibodies to either the nucleocapsid or spike protein. Here we compare the performance of the Beckman-Coulter SARS-CoV-2 spike IgG assay to that of the Abbott SARS-CoV-2 nucleocapsid IgG and Roche Anti-SARS-CoV-2 nucleocapsid total antibody assays. In addition, we document the trend in nucleocapsid and spike antibodies in sequential samples collected from convalescent plasma donors. MethodsPlasma or serum samples from 20 individual SARS-CoV-2 RT-PCR-positive inpatients (n = 172), 20 individual convalescent donors with a previous RT-PCR-confirmed SARS-CoV-2 infection (n = 20), were deemed positive SARS-CoV-2 samples. RT-PCR-negative inpatients (n = 24), and 109 pre-SARS-CoV-2 samples were determined to be SARS-CoV-2 negative. Samples were assayed by the Abbott, Roche, and Beckman assays. ResultsAll three assays demonstrated 100% specificity. Abbott, Beckman, and Roche platforms had sensitivities of 98%, 93%, and 90% respectively, with the difference in sensitivity attributed primarily to samples from immunocompromised patients. After the exclusion of samples immunocompromised patients, all assays exhibited ≥ 95% sensitivity. In sequential samples collected from the same individuals, the Roche nucleocapsid antibody assay demonstrated continually increasing signal intensity, with maximal values observed at the last time point examined. In contrast, the Beckman spike IgG antibody signal peaked between 14 and 28 days post positive SARS-CoV-2 PCR and steadily declined in subsequent samples. Subsequent collections 51–200 days (median of 139 days) post positive SARS-CoV-2 RT-PCR from five inpatients and five convalescent donors revealed that spike and nucleocapsid antibodies remained detectable for several months after confirmed infection. ConclusionsThe three assays are sensitive and specific for SARS-CoV-2 antibodies. Nucleocapsid and spike antibodies were detectable for up to 200 days post-positive SARS-CoV-2 PCR but demonstrated markedly different trends in signal intensity.

Performance of an automated chemiluminescent immunoassay for SARS-COV-2 IgM and head-to-head comparison of Abbott and Roche COVID-19 antibody assays

IntroductionWe evaluated the performance of the new Abbott SARS-CoV-2 IgM assay on the Architect immunoassay analyser and compared it to the Architect IgG/Roche Cobas total antibody assays in both SARS-CoV-2 RT-PCR positive cases and healthy controls. Method200 healthy control samples and 48 individuals with other antibody-positive disorders (18 hepatitis/18 dengue/11 ANA/1 dsDNA) served to assess for potential cross-reactivity. Anonymised residual leftover sera positive for SARS-CoV-2 on RT-PCR were recruited as cases (N ​= ​133). The sensitivity/specificity/cross-reactivity of the Architect IgM assay were assessed. Concordance between the 3 assays were also analysed. ResultsThere was no cross-reactivity with controls and other antibody positive samples. The Architect IgM assay was 100% specific (95% CI 98.5 to 100) and sensitivity was 77.8% (95% CI 60.8 to 89.9) ≥14 days post-first positive RT-PCR (POS). Sensitivity of the combined Architect IgM and IgG results (30.8%) was significantly better than the Cobas total antibodies (15.4%) in early disease (p ​= ​0.04). While the Architect IgM assay had moderate agreement with the Cobas total antibody result (Cohen’s kappa 0.72), a combined Architect IgM and IgG result had better agreement (Cohen’s kappa 0.83). ConclusionThe Architect IgM assay has good specificity and no cross-reactivity with other antibody positive cases. A combined Architect IgM and IgG result has better sensitivity than the individual assays for early COVID-19. The Architect IgM assay is not comparable to the Cobas total antibody assay, but the Architect IgM and IgG combined result has good agreement with the Cobas assay.

Evaluation of three commercial SARS-CoV-2 serology assays in a tertiary care hospital in the United Arab Emirates

BackgroundSerology assays have the potential to support RT-PCR in the diagnosis of SARS-CoV-2 infection. We studied three commercially available immunoassays for their diagnostic accuracy from blood specimens collected from 93 patients. MethodsBlood samples from patients with confirmed COVID-19 infection were analysed using three different Immunoassays (Roche total antibody assay, Abbott IgG assay and Euroimmun IgG assay). Sensitivity, specificity, precision and time of seroconversion were evaluated. ResultsThe sensitivity of Roche, Abbott and Euroimmun assays was 38.7%, 35.5% and 25.0% respectively for specimens collected <10 days and 84.4%, 84.4% and 70.0% respectively for specimens collected ≥10 days after the first positive RT-PCR. The specificity of all the three assays in this study was 100%. The timing of seroconversion occurred at day 1, 7 or 14. ConclusionsThe assays evaluated in this study have different sensitivities for detecting antibodies in SARS-CoV-2 infection. Sensitivity for detecting antibodies for all three assays was higher for specimens collected ≥10 days after first positive PCR compared with specimens collected <10 days. Time of seroconversion is variable and assay-dependent.