Seroconversion among COVID-19 patients admitted in a dedicated COVID hospital: A longitudinal prospective study of 1000 patients

Abstract

Background The immune response after SARS-CoV-2 is complex and may be affected by severity of the disease, race, etc. The present study was conducted to assess the serial antibody response among the COVID-19 patients admitted in the hospital. Methods The study was conducted between July and October 2020 in a dedicated COVID-19 hospital. All consented patients underwent serial testing of antibodies using a rapid chromatographic immunoassay-based qualitative IgG/IgM kit every third day until their discharge or death. The data about age, sex, severity of disease, length of stay, onset of symptoms, date of molecular testing were also collected. Appropriate statistical tests were used. Results The mean age of 1000 COVID-19 patients was 47.5 ± 17.9 years. Out of the total, 687 (68.7%) were males. With respect to severity, 682 (68.2%) were asymptomatic/mild, 200 (20%) were moderate and 118 (11.8%) were severe cases. The seroconversion percentage increased from 12.8% to 97.9% and 16.3% to 80.9% for IgG and IgM respectively in 21 days. The median time for seroconversion was 10 days (IQR:6–12 days) for IgG and eight days (IQR: 6–11 days) for IgM. At the time of discharge (median nine days), detectable IgG and IgM antibodies were present in 502 (52.46%) and 414 (43.26%) participants respectively. Seroconversion was associated with days after the symptoms, increasing severity of the disease and the presence of co-morbidity. Conclusion Seroconversion increased during the period of observation. The severe/moderate cases of COVID-19 tend to have an early seroconversion as compared to the asymptomatic/mild cases. Only half of the patients were seroconverted at discharge.

Longitudinal, virological, and serological assessment of hospitalized COVID-19 patients

“…As expected, the antibody titers significantly increased over the time, reaching the almost complete seroconversion to IgG, about 17–19 days after symptoms onset. This is in line with reports from the literature, concluding that the rate and timing of IgM and IgG seroconversion were inconsistent across the independent analyzed studies, but most seroconverted for IgG within 2 weeks and 100% within 4 weeks (O Murchu et al 2020 ; Yadav et al 2021 ).…”

Profile of Serological (IgM/IgG) and Virological Markers of COVID-19 in Some Private Universities in Cameroon During the Pandemic

“…These may be false-negative or evidence that these are early infections with levels of antibodies that cannot be detected by the serological tests we used [35]. Moreover, it could be related to seroconversion, a period the onset of antibody production which will the rise to detectable [57], [58]. In addition, numerous studies have already reported a low sensitivity of the COVID IgM/IgG serological tests compared to techniques such as ELISA or LUMINEX [59]- [63] suggesting a continuous readaptation of prefabricated RDTs in the emergency anti-COVID response is needed, especially as circulating strains arise and cause new waves.…”

Comparative Performance of Serological (IgM/IgG) and Molecular Testing (RT-PCR) of COVID-19 in Three Private Universities in Cameroon during the Pandemic

“…These may be false negatives or evidence that these are early infections with levels of antibodies that cannot be detected by the serological tests we used [ 36 ]. Moreover, it could be related to seroconversion, a period before the onset of antibody production, which will increase detectability [ 56 , 57 , 58 ]. In addition, numerous studies have already reported low sensitivity of COVID IgM/IgG serological tests compared to techniques such as ELISA or LUMINEX [ 59 , 60 , 61 , 62 , 63 ], suggesting a continuous readaptation of prefabricated RDTs in the emergency anti-COVID response is needed, especially as circulating strains arise and cause new waves.…”