key: cord-0706993-k5yao113
authors: Chew, Ka Lip; Tan, Shaun S.; Saw, Sharon; Pajarillaga, Anastacia; Zaine, Suzzana; Khoo, Candy; Wang, Weixuan; Tambyah, Paul; Jureen, Roland; Sethi, Sunil K.
title: Clinical evaluation of serological IgG antibody response on the Abbott Architect for established SARS-CoV-2 infection
date: 2020-06-09
journal: Clin Microbiol Infect
DOI: 10.1016/j.cmi.2020.05.036
sha: 15bdfd7aaac9ccd3da099dc3bd9ccba89f9e7fe9
doc_id: 706993
cord_uid: k5yao113

OBJECTIVE: This study aimed to evaluated the diagnostic performance of the Abbott Architect SARS-CoV-2 IgG assay in COVID-19 patients. METHODS: Residual sera from 177 symptomatic COVID-19 positive patients, and 163 non-COVID-19 patients were tested for antibody with the Abbott SARS-CoV-2 IgG assay (Abbott Diagnostics, Chicago, US). Clinical records for COVID-19 patients were reviewed to determine the time from onset of clinical illness to testing. RESULTS: Specificity of the assay was 100.0% (95% CI: 97.1 – 100.0%). The clinical sensitivity of the assay varied depending on time from onset of symptoms, increasing with longer periods since onset of clinical illness. The clinical sensitivity at ≤6 days was 8.6% (7/81; 95% CI: 3.8 – 17.5%), 7-13 days: 43.6% (17/39; 95% CI: 28.2 – 60.2%), 14-20 days: 84.0% (21/25; 95% CI: 63.1 – 94.7%), and ≥21 days: 84.4% (27/32; 95% CI: 66.5 – 94.1%). Clinical sensitivity was higher in the ≥14 days group compared to <14. There were no differences between the 14-20 days and ≥21 days group; the combined clinical sensitivity for these groups (≥14 days) was 84.2% (49/57; 71.6 – 92.1%). CONCLUSION: The Abbott SARS-CoV-2 IgG test has high specificity. Clinical sensitivity was limited in early stages of disease but improved from 14 days after onset of clinical infection.

There is interest in developing other testing modalities for confirmation of diagnosis such as 45 antigen testing and serological assays [1] . SARS-CoV-2 antibody response may comprise of clinical utility of serology testing as a diagnostic tool. In this study, we aimed to test the 51 Abbott Architect SARS-CoV-2 IgG on our Abbott Architect i4000SR analyzer, which has a 52 throughput of 400 tests per hour. A cohort of positive COVID-19 patients' residual sera were 53 utilized for testing, and we established the clinical sensitivity and specificity of the assay to 54 determine the utility of SARS-CoV-2 IgG detection.

Methods: 57 We prospectively identified confirmed COVID-19 patients presenting to and admitted to our 58 institution from 30 th of March 2020 to 15 th of May 2020. Patients were selected on the basis 59 of a positive SARS-CoV-2 rRT-PCR from a respiratory sample. Residual sera were collected 60 from this cohort and stored for serological testing. Samples were handled in strict accordance 61 to the WHO biosafety precautions as previously described [3] . Two PCR assays were used Clinical sensitivity was higher in the ≥14 days group compared to <14. There were no 108 differences between the 14-20 days and ≥21 days group; the combined clinical sensitivity for 109 these groups (≥14 days) was 84.2% (49/57; 71.6 -92.1%).

The S/CO values are summarized in Table 1 . The maximum S/CO detected for negative cases 112 was 0.70. The clinical sensitivity was calculated again using S/CO of 1.0 and 0.8 for 113 classifying reactive vs non-reactive results. These are summarized in Table 2 . At a cut-off of A number of cases remained negative even after ≥14 days after the onset of illness. In light 164 progressively increasing S/CO and high specificity of the assay, we propose that 165 modifications to the cut-off for determining reactivity may be considered. In Table 2 , The correlation between antibody production and outcomes or long-term immunity has not is unlikely [7] . Further work is required in determining whether the presence of neutralizing 180 antibodies confer long-term immunity in humans. This is vital for several reasons including In conclusion, the Abbott SARS-CoV-2 IgG test has high technical specificity. There is 195 potential room for improving clinical sensitivity of the assay to detect previous infection. 

The epidemiology, diagnosis and 220 treatment of COVID-19

SARS-CoV-2 in patients with COVID-19

Practical laboratory 225 considerations amidst the COVID-19 outbreak: early experience from Singapore

Clinical Performance of Two SARS-CoV-2 Serologic Assays

A serological assay to detect SARS-CoV-2 seroconversion in humans

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Lack of Reinfection in Rhesus 237

Macaques Infected with SARS-CoV-2, bioRxiv

SARS-CoV-2 Serology: Much Hype, Little Data

of interest to declare. 207 Acknowledgements: 208 We would like to thank Temasek Holdings Pte Ltd for sponsoring the laboratory testing kits 209 used in this study.