J Clin Microbiol . Clinical evaluation of the Abbott Alinity SARS-CoV-2 spike-specific quantitative IgG and IgM assays among infected, recovered, and vaccinated groups

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J Clin Microbiol


. 2021 Apr 7;JCM.00388-21.
doi: 10.1128/JCM.00388-21. Online ahead of print.
Clinical evaluation of the Abbott Alinity SARS-CoV-2 spike-specific quantitative IgG and IgM assays among infected, recovered, and vaccinated groups


Madhusudhanan Narasimhan ¹ , Lenin Mahimainathan, Ellen Araj ¹ , Andrew E Clark ¹ , John Markantonis ¹ , Allen Green ¹ , Jing Xu ¹ , Jeffrey A SoRelle ¹ , Charles Alexis ¹ , Kimberly Fankhauser ¹ , Hiren Parikh ¹ , Kathleen Wilkinson ² , Annika Reczek ² , Noa Kopplin ² , Sruthi Yekkaluri ² , Jyoti Balani ¹ , Abey Thomas ² , Amit G Singal ² , Ravi Sarode ^{1 2} , Alagarraju Muthukumar ³



Affiliations

• PMID: 33827901
• DOI: 10.1128/JCM.00388-21

Abstract

The COVID-19 pandemic continues to impose a significant burden on global health infrastructure. While identification and containment of new cases remains important, laboratories must now pivot and consider an assessment of SARS-CoV-2 immunity in the setting of the recent availability of multiple COVID-19 vaccines. Here we have utilized the latest Abbott Alinity semi-quantitative IgM and quantitative IgG spike protein (SP) serology assays (IgM_SP and IgG_SP) in combination with Abbott Alinity IgG nucleocapsid (NC) antibody test (IgG_NC) to assess antibody responses in a cohort of 1236 unique participants comprised of na?ve, SARS-CoV-2 infected, and vaccinated (including both na?ve and recovered) individuals. The IgM_SP and IgG_SP assays were highly specific (100%) with no cross-reactivity to archived samples collected prior to the emergence of SARS-CoV-2, including those from individuals with seasonal coronavirus infections. Clinical sensitivity was 96% after 15 days for both IgM_SP and IgG_SP assays individually. When considered together, the sensitivity was 100%. A combination of NC- and SP-specific serologic assays clearly differentiated na?ve, SARS-CoV-2-infected, and vaccine-related immune responses. Vaccination resulted in a significant increase in IgG_SP and IgM_SP values, with a major rise in IgG_SP following the booster (second) dose in the na?ve group. In contrast, SARS-CoV-2 recovered individuals had several fold higher IgG_SP responses than na?ve following the primary dose, with a comparatively dampened response following the booster. This work illustrates the strong clinical performance of these new serological assays and their utility in evaluating and distinguishing serological responses to infection and vaccination.