Cross-sectional assessment of a history of SARS-CoV-2 infections using IgG
More details
Hide details
Department of Biochemistry, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Poland
School of Medicine, Collegium Medicum, University of Warmia and Mazury, Poland
Department of Rehabilitation and Orthopedics, School of Medicine, Collegium Medicum, University Warmia and Mazury in Olsztyn, Poland
Department of Surgery, School of Public Health, Collegium Medicum, University of Warmia and Mazury in Olsztyn, Poland
Department of Ophthalmology, School of Medicine, Collegium Medicum, University of Warmia and Mazury in Olsztyn, Poland
Institute for Research in Ophthalmology, Foundation for Ophthalmology Development, Poznan, Poland
Submission date: 2022-07-29
Final revision date: 2023-02-21
Acceptance date: 2023-02-21
Online publication date: 2023-10-17
Corresponding author
Dominika Rozmus   

Department of Biochemistry, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Oczapowskiego 1A, 10-719 Olsztyn, Poland
Pol. Ann. Med. 2023;30(2):91–95
Severe acute respiratory syndrome, coronavirus type 2 (SARS-CoV-2) has become a global threat for every healthcare system, and the coronavirus disease 2019 (COVID-19) pandemic has resulted in over 3 million deaths worldwide. SARS-CoV-2 brings symptoms such as fever, cough, shortness of breath, headache, sore throat and loss of taste or smell. Diagnostic of COVID-19 may include specific RT-PCR for viral ribonucleic acid detection, and ELISA testing for virus-derived spike protein or nucleocapsid.

The aim of this study was to measure the antinucleocapsid level of SARS-CoV-2 IgG to identify the number of asymptomatic cases of COVID-19 after infection in a population of workers from a production company.

Material and methods:
Human anti-SARS-CoV-2(N) IgG ELISA kit was used to determine serum IgG level. Study includes 107 individuals (48% female, 52% male) in different ages (18–60 years).

Results and discussion:
Of 107 tested individuals in 80 (74.7%) cases SARS-CoV-2(N)-specific IgG antibodies were detected, with an average antibody concentration of the whole study group 4.08 µg/mL (n = 107 with the range 0.59–7.91 µg/mL; n = 80 were included in the study with the sensitivity of the method above 2.344 µg/mL). In only 9 cases, SARS-CoV-2 infection was confirmed before using the PCR test. Our data underscore the need for a population study in Poland to test the proportion of asymptomatic IgG positive for SARS-CoV-2 individuals.

This study indicates that within studied sample large proportion of asymptomatic people have undergone SARS-CoV-2 infection and suggests that isolation of only symptomatic patients would not stop the transmission of the virus.

The authors are grateful to Mr. Mirosław Żywicki for his support in this study.
This research received no external funding.
Authors declare no conflict of interests.
Worldometers. COVID-19 Coronavirus Pandemic. Accessed: March 25, 2021.
CDC. Healthcare Workers. Centers for Disease Control and Prevention. Published: February 11, 2020. Accessed: March 28, 2021.
Romaszko-Wojtowicz AM, Doboszyńska A. Pulmonary complications due to COVID-19 – a literature review. Pol Ann Med. 2021;28(2):244–249.
Berlin DA, Gulick RM, Martinez FJ. Severe Covid-19. Solomon CG, ed. N Engl J Med. 2020;383(25):2451–2460.
Sethuraman N, Jeremiah SS, Ryo A. Interpreting Diagnostic Tests for SARS-CoV-2. JAMA. 2020;323(22):2249–2251.
Tré-Hardy M, Wilmet A, Beukinga I, et al. Analytical and clinical validation of an ELISA for specific SARS-CoV-2 IgG, IgA, and IgM antibodies. J Med Virol. 2021;93(2):803–811.
Mathuria JP, Yadav R, Rajkumar. Laboratory diagnosis of SARS-CoV-2 – A review of current methods. Infect Public Health. 2020;13(7):901–905.
Zhou W, Xu X, Chang Z, et al. The dynamic changes of serum IgM and IgG against SARS-CoV-2 in patients with COVID-19. J Med Virol. 2021;93(2):924–933.
Isho B, Abe KT, Zuo M, et al. Persistence of serum and saliva antibody responses to SARS-CoV-2 spike antigens in COVID-19 patients. Sci Immunol. 2020;5(52):eabe5511.
Dan JM, Mateus J, Kato Y, et al. Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection. Science. 2021;371(6529):eabf4063.
Lee HK, Lee BH, Seok SH, et al. Production of specific antibodies against SARS-coronavirus nucleocapsid protein without cross reactivity with human coronaviruses 229E and OC43. J Vet Sci. 2010;11(2):165–167.
Long QX, Liu BZ, Deng HJ, et al. Antibody responses to SARS-CoV-2 in patients with COVID-19. Nat Med. 2020;26(6):845–848.
Kasper MR, Geibe JR, Sears CL, et al. An Outbreak of Covid-19 on an Aircraft Carrier. NEJM. 2020;383(25):2417–2426.
Qian H, Miao T, Liu L, Zheng X, Luo D, Li Y. Indoor transmission of SARS-CoV-2. Indoor Air. 31(3):639–645.
Johansson MA, Quandelacy TM, Kada S, et al. SARS-CoV-2 Transmission From People Without COVID-19 Symptoms. JAMA Netw Open. 2021;4(1):e2035057.
Buonanno G, Morawska L, Stabile L. Quantitative assessment of the risk of airborne transmission of SARS-CoV-2 infection: Prospective and retrospective applications. Environ. Int. 2020;145:106112.
WHO. Coronavirus. Accessed: July 13, 2022.
Website of the Republic of Poland. Report of coronavirus infections (SARS-CoV-2). Coronavirus: information and recommendations [in Polish]. Accessed September 5, 2021.
Ochal M, Kuchta R, Tokarczyk-Malesa K, Romaszko M, Skutecki R. A COVID-19 Micro-epidemic in the Shelter for the Homeless in Olsztyn. Pol Ann Med. 2021;28(2):194–198.