Immunogenetics: Open Access

Immunogenetics: Open Access
Open Access

Commentary - (2020)Volume 5, Issue 1

Performance Assessment of First-Generation Anti-SARS-CoV-2 Serological Assays

Tahir S Shamsi, Tahir S Shamsi*, Mehjabeen Imam, Shabnum Khawaja, Arshi Naz, Ahson Siddiqui, Naveen Tariq and Salman Tariq
*Correspondence: Tahir S Shamsi, National Institute of Blood Diseases & Bone Marrow Transplantation, Karachi, Country Advisor, Royal College of Pathologists, UK, Pakistan, Tel: +922134821502-3, Email:

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Clinical and epidemiological use of SARS-CoV-2 antibody assays is under debate. Commercial manufacturers have developed first- generation serological kits. FDA approval is for Emergency Use Authorization (EUA) [1]. Verification and validation of these assays is required to achieve the accuracy of test results [2]. There are several advantages of serological testing, like, easy sample collection, simplicity, and minimal technical expertise. Most importantly, the results of this testing will be useful for epidemiological studies, disease surveillance and in monitoring response to the vaccine [3]. We performed the assessment of commercial serological assays of anti-SARS-CoV-2 antibodies using different techniques and checked the seroprevalence in our population. Between April 2020 to July 2020, (shown in Table 1) four-hundred and four subjects were tested; convalescent plasma donors (CPDs n=239), health care professionals (HCPs n=44), healthy blood donors (HBDs n=70) and from community (n=51) at National Institute of Blood Diseases (NIBD) hospital Karachi. We evaluated the performance of Electro Chemi Luminescence Assay (ECLIA) on Cobas-e411 by Roche, three qualitative anti-SARS-CoV-2-IgG Enzyme Linked Imunosorbant Assay (ELISA) by (Generic assays, Euroimmun and Omega diagnostics),one quantitative ELISA assay by AESKU Diagnostics, and two immune chromatography (ICT) kits namely InstaTestTM by CORTEZ and TEST IT by TURKLAB . Out of the total 404 subjects, 342 (84.6%) were males. Mean age of the subjects was 36.79 ± 11.95 years. Two-hundred and two (84.5%) of 239 CPDs group showed positive total (IgM/IgG) antibodies by ECLIA. Only 174 of these 239 (72.8%) CPDs, qualitative IgG-ELISA was positive while quantitative IgG-ELISA showed seropositivity in 180 (75.3%) of them with a mean IgG level of 56.7 ± 39.7 U/ml. Of 44 RT-PCR proven HCP cases,anti-SARS-CoV-2 antibodies were detected in 7 of 13 (53.8%) and 14 of 18 (77.77%) on 7-8 days and 12-14 days respectively; ECLIA was used . Of the 70 HBDs, ECLIA and quantitative IgG-ELISA showed seropositivity in 15 (21.4%) and 14 (20.0%) respectively. Mean IgG antibody level of 27.2 ± 19.95 U/ml was detected. Twelve of 51 (23.6%) patients from the community had active COVID disease detected via RT-PCR and three out of these 12 (25%) showed seropositivity on ECLIA.

No Group Inclusion criteria
01 Convalescent plasma donors (CPDs) for COVID-19 Adult corona survivors of either gender aged 18 to 60 years, with no comorbidities, fully recovered from COVID-19 for at least two weeks [4].  
02 Health care professionals (HCPs) Hospital staff of either gender aged 18 to 60 years who were experiencing symptoms associated with COVID-19 including fever, dry cough, body aches, flu-like symptoms, sore throat, new loss of taste or smell and difficulty in breathing [5]. Their PCR was done along with serological testing.
03 People from community Convalescent plasma donorsspread the awareness and urged their closed acquaintances to get them tested for COVID-19, along with them walk-in patients who were tested for PCR and anti SARS-CoV-2 IgG simultaneously were also taken in this group.
04 Healthy blood donors (HBDs) Regular blood donors were recruited in this group and after their consent we tested them for anti-SARS-CoV-2antibodies.

Table 1: Inclusion Criteria of our study.


The diagnostic performance (sensitivity, specificity, PPV and NPV) of all the serological assays shown in Table 2. We evaluated the performance of three different serological assays in four different groups. The performance characteristics of different kits, e.g., sensitivity claimed by their manufacturers, fell short since our calculated sensitivities were below that of the manufacturers’ claim. This finding is in accordance with an Australian report published on 29th April 2020 [6]. Mei San Tang et al. compared Abbott Chemiluminescence assay and ELISA within 5 days of onset of symptoms, none of the immunoassays was able to detect the antibodies [6]. This finding is similar with our results and was in contrast with the manufacturer’s claim that for ECLIA by Roche showed 65.5% (CI 56%-74%) sensitivity when tested within 6 days PCR confirmation. Out of our 239 CPDs, 37 (15.5%) did not develop antibodies against SARS-CoV-2 virus by any of the testing method i.e. ECLIA, quantitative and qualitative ELISA. All these kits were developed to detect antibodies against viral nucleocapsid. If some of these subjects developed anti-S1 spike protein antibodies, then they would have been missed by these kits. Alternatively, cellular immunity might have been developed in these seronegative CP donors as per Shane et al. [7]. The HBDs had no symptoms of COVID-19 infection, they were healthy and active; one-fifth of them seroconverted.

Serological assays Sensitivity Specificity PPV  NPV
ECLIA# (Roche Diagnostics) 97.44% a  99% b 99% e 90.9% f
Qualitative ELISA$ (Generic Assays) 67.85% c 89.9% c 95% c 70.96% c
Qualitative ELISA$ (EUROIMMUN) 90.38% c 94.9% c 96.8% c 88.88% c
Qualitative ELISA$ (Omega Diagnostics) 95.4% c 95.2% c 98.8% c 86.95% c
Quantitative ELISA (AESKULISA) 93.75% d 100% b 100% g 80.64% h
IgM/IgG ICT (Cortez)* 90.4% c 99% c 99% c 83.4% c
IgM/IgG ICT (Turk Lab)* 23.53% c 99% c 99% c 43.4% c

Table 2: Diagnostic performance of all the serological assays used in the study


This is a significant finding, unreported until now, as it highlights the prevalence of this disease in general population. Limitation of study was that we could not perform RT-PCR of healthy blood donors and ELISA of HCPs and people from community due to cost limitation.


  1. U.S. Department of Health and Human Services. Determination of a Public Health Emergency and Declaration that Circumstances Exist Justifying Authorizations Pursuant to Section 564(b) of the Federal Food, Drug, and Cosmetic Act, 21 U.S.C. 2020;360:bbb-3.
  2. Marca AL, Capuzzo M, Paglia T. Testing for SARS-CoV-2 (COVID-19): A systematic review and clinical guide to molecular and serological in-vitro diagnostic assays. Reprod BioMed Online 2020.
  3. Tang Mei San, Hock Karl G, Logsdon Nicole M. Clinical Performance of Two anti-SARS-CoV-2SerologicAssays. Clin Chem. 2020;66(8): 1055-1062.
  4. Bond K, Nicholson S, Hoang T, Catton M. Post-market validation of three serological assays for COVID-19. 2020.
  5. Grifoni A, Weiskopf D, Ramirez SI. Targets of T cell responses to SARS-CoV-2 coronavirus in humans with COVID-19 disease and unexposed individuals. Cell. 2020;181(7): 1489-1501.

Author Info

Tahir S Shamsi, Tahir S Shamsi*, Mehjabeen Imam, Shabnum Khawaja, Arshi Naz, Ahson Siddiqui, Naveen Tariq and Salman Tariq
National Institute of Blood Disease and Bone Marrow Transplantation (NIBD), Karachi, Pakistan

Citation: Shamsi T, Imam M, Khawaja S, ArshiNaz, Siddiqui A, Tariq N et al. (2020) Performance Assessment of First-Generation Anti-SARS-CoV-2 Serological Assays. Immunogenet Open Access. 5:127.

Received: 15-Nov-2020 Accepted: 30-Nov-2020 Published: 07-Dec-2020 , DOI: 10.35248/igoa.20.5.127

Copyright: © 2020 Shamsi T, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.