IgM and IgG Antibody Levels in Patients with COVID-19 in South Andhra Pradesh


Kiranmayi Bogarapu1, Aruna P.2,

Coronavirus disease - 19 (COVID-19) is an infectious disease caused by a newly
discovered coronavirus, severe acute respiratory syndrome coronavirus 2 (SARSCoV-
2). Anti-SARS-CoV-2 IgM and IgG antibodies can be detected in almost all
patients of COVID-19. We sought to evaluate the antibody responses in COVID-
19 patients and also analyse their potential role in disease prognostication.
All consecutive COVID-19 patients, between ages 20 - 65 years, encountered
between April and July 2020 were included and compared to age-matched
controls. Severity of the SARS-CoV-2 infection was categorized as none, mild and
severe, based on the presence of symptoms, oxygen saturation and need for
respiratory support. Serum levels of IgM and IgG antibody assays were obtained,
using chemiluminescence immunoassay, after the 2nd week of presentation (range
14 - 60 days). Antibody titres above 10 AU/ml were taken as elevated.
Of 50 eligible patients, majority (40/50, 80 %) had mild symptoms and oxygen
saturations above 94 %. Of the remainder, 10 % (5/50) had severe infection with
need for either high flow nasal cannula oxygen or mechanical ventilation while the
remainder (10 %; 5/50) were asymptomatic. IgM and IgG seroconversion were
noted in almost all COVID-19 patients (46/50, 92 %) compared to healthy controls.
While elevated IgG antibody levels were noted in 76 % (38/50), combined
elevation of IgM and IgG antibodies is seen in 16 % (8/50) of patients.
Seroconversion was markedly profound in patients with severe infection than
those with mild infection. Also, greater seroconversion was noted after 21 days of
testing compared to 14th day, especially for IgG.
Antibody seroconversion to SARS-CoV-2 occurred in majority of patients with
COVID-19, with most salient increase in the IgG antibody levels. Antibody titres
correlated directly to the disease severity, suggestive of the potential value of
antibodies not only in diagnosis but also in prognostication.