Evaluation of Antibody Response in Symptomatic and Asymptomatic COVID-19 Patients and Diagnostic Assessment of New IgM/IgG ELISA Kits

Abstract

This study aims to study the immune response and evaluate the performances of four new IgM and five IgG enzyme-linked immunosorbent assay (ELISA) kits for detecting anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies against different antigens in symptomatic and asymptomatic coronavirus disease 2019 (COVID-19) patients. A total of 291 samples collected from symptomatic and asymptomatic RT–PCR-confirmed patients were used to evaluate the ELISA kits’ performance (EDI, AnshLabs, DiaPro, NovaLisa, and Lionex). The sensitivity was measured at three different time-intervals post symptoms onset or positive SARS-CoV-2 RT–PCR test (≤14, 14–30, >30 days). The specificity was investigated using 119 pre-pandemic serum samples. The sensitivity of all IgM kits gradually decreased with time, ranging from 48.7% (EDI)–66.4% (Lionex) at ≤14 days, 29.1% (NovaLisa)–61.8% (Lionex) at 14–30 days, and 6.0% (AnshLabs)–47.9% (Lionex) at >30 days. The sensitivity of IgG kits increased with time, peaking in the latest interval (>30 days) at 96.6% (Lionex). Specificity of IgM ranged from 88.2% (Lionex)–99.2% (EDI), while IgG ranged from 75.6% (DiaPro)–98.3% (Lionex). Among all RT–PCR-positive patients, 23 samples (7.9%) were seronegative by all IgG kits, of which only seven samples (30.4%) had detectable IgM antibodies. IgM assays have variable and low sensitivity, thus considered a poor marker for COVID-19 diagnosis. IgG assays can miss at least 8% of RT–PCR-positive cases.

Trends of SARS-CoV-2 antibody prevalence in selected regions across Ghana

“…Antibody cross-reactivity with other pathogens is often manifested in IgM detection [49, 50]. During validation, and in the field, detection of IgM was uncommon, and when detected, IgM was often accompanied by IgG.…”

Detection of Anti-Nucleocapsid Antibody in COVID-19 Patients in Bangladesh Is not Correlated with Previous Dengue Infection

“…The S-protein immunoassays reliably detect antibody responses to S-protein and S protein ACE-2 RBD in COVID-19 vaccination trials [ 43 , 44 ]. Third, the N-protein ELISA from different manufacturers show analytical sensitivities ranging from 82 to 99 percent and analytical specificities ranging from 98 to 100 percent for specific IgA and IgG on day 7 to day 14 after rT-PCR confirmed SARS-CoV-2 infection [ 45 , 46 , 47 , 48 , 49 , 50 ]. In some cases, the N-protein specific IgA levels increase by 10 to 100-fold above the immunoassay cut-off, indicating a rigorous mucosal immune response to SARS-CoV-2 [ 51 ].…”

“…The kinetics and magnitude of the SARS-CoV-2 antibody response was determined by comparing the percent positivity and the levels of anti-N-protein antibody at day one to day eight and at follow up intervals days 15 to 28, days 42 to 62 and days 65 to 177 post-onset of COVID-19 symptoms. The N-protein Novalisa uses glycosylated recombinant C-terminus of the SARS-CoV-2 N-protein, which, in a previous evaluation with 119 pre-pandemic control serum, including 14 serum with reactivity against MERS-CoV or seasonal coronaviruses, gave no false positive anti-N-protein IgG test results [ 47 , 48 ].…”

“…The Novatec units of antibody activity is established as a validated index for the semi-quantitative determination of anti-SARS-CoV-2 specific IgA [ 49 , 50 ] and IgG [ 48 , 49 , 50 ] at the manufacturer cut-off of 10 U/L. The analytical sensitivity 95% (95% CI 83–98%) and specificity 96% (95% CI 89–99%) for anti-N-protein IgG and the sensitivity of 90% (95% CI 76–96%) and specificity of 99% (95% CI 93–99%) for anti-N-protein IgA was previously determined on 208 Belgian patients with moderate to severe COVID-19 symptoms between days 14 to 18 after the onset of symptoms and 79 pre-COVID-19 pandemic serum representatives of various non-flavivirus and non-coronavirus infectious diseases [ 50 ].…”

“…In German health care workers with mild to moderate COVID-19 disease, the Novatec N-protein IgG ELISA gave a sensitivity of 72% (95% CI 51–88 %) at 14 to 21 days rT-PCR SARS-CoV-2 positivity, slightly lower than the 80% sensitivity reported by automated N-protein immunoassays of Siemens, Roche and Abbott [ 46 ]. The anti-N-protein IgG percent positives in Novalisa were 64, 87 and 88 percent at less than 7 days, 8 to 14 days and greater than 14 days post-onset of COVID-19 symptoms, respectively, in 101 Qatar patients with rT-PCR confirmed COVID-19 [ 48 ]. However, in Bangladesh, we cannot rule out exposures to coronaviruses pre-COVID-19 pandemic that may give rise to positive reactivity in the N-protein Novalisa.…”