Case-Control Study of Individuals with Discrepant Nucleocapsid and Spike Protein SARS-CoV-2 IgG Results.
Clin Chem
; 67(7): 977-986, 2021 07 06.
Article
in English
| MEDLINE | ID: covidwho-1132473
ABSTRACT
BACKGROUND:
Laboratory-based methods for SARS-CoV-2 antibody detection vary widely in performance. However, there are limited prospectively-collected data on assay performance, and minimal clinical information to guide interpretation of discrepant results.METHODS:
Over a 2-week period, 1080 consecutive plasma samples submitted for clinical SARS-CoV-2 IgG testing were tested in parallel for anti-nucleocapsid IgG (anti-N, Abbott) and anti-spike IgG (anti-S1, EUROIMMUN). Chart review was conducted for samples testing positive or borderline on either assay, and for an age/sex-matched cohort of samples negative by both assays. CDC surveillance case definitions were used to determine clinical sensitivity/specificity and conduct receiver operating characteristics curve analysis.RESULTS:
There were 52 samples positive by both methods, 2 positive for anti-N only, 34 positive for anti-S1 only, and 27 borderline for anti-S1. Of the 34 individuals positive for anti-S1 alone, 8 (24%) had confirmed COVID-19. No anti-S1 borderline cases were positive for anti-N or had confirmed/probable COVID-19. The anti-N assay was less sensitive (84.2% [95% CI 72.1-92.5%] vs 94.7% [95% CI 85.4-98.9%]) but more specific (99.2% [95% CI 95.5-100%] vs 86.9% [95% CI 79.6-92.3%]) than anti-S1. Abbott anti-N sensitivity could be improved to 96.5% with minimal effect on specificity if the index threshold was lowered from 1.4 to 0.6.CONCLUSION:
Real-world concordance between different serologic assays may be lower than previously described in retrospective studies. These findings have implications for the interpretation of SARS-CoV-2 IgG results, especially with the advent of spike antigen-targeted vaccination, as a subset of patients with true infection are anti-N negative and anti-S1 positive.Keywords
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
Immunoglobulin G
/
Nucleocapsid
/
Spike Glycoprotein, Coronavirus
/
SARS-CoV-2
/
COVID-19
/
Antibodies, Viral
Type of study:
Cohort study
/
Diagnostic study
/
Observational study
/
Prognostic study
Topics:
Vaccines
Limits:
Adult
/
Female
/
Humans
/
Male
/
Middle aged
Language:
English
Journal:
Clin Chem
Journal subject:
Chemistry, Clinical
Year:
2021
Document Type:
Article
Affiliation country:
Clinchem
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