BlueDiver COVIDOT 5 IgG is an Immunodot kit intended for the In Vitro detection, in human serum, of IgG antibodies against SARS-COV-2 antigens.
The assay uses recombinant proteins representing the following SARS-CoV-2 antigens:
- The Nucleocapsid (N) protein
- The Spike (S) protein (ECD, ectodomain, S1 + S2)
- The S1 subunit of the S-protein
- The S2 subunit of the S-protein
- The RBD (Receptor Binding Domain) of the S1 subunit
The test is intended as an aid in the determination of the immune response to SARS-CoV-2 infection, to support the diagnosis of the COVID-19 disease.
This kit is for professional use only. The kit is intended to be used on a BlueDiver Instrument.
Clinical Sensitivity
During the first month after initial infection, the clinical sensitivity of a serological test depends on when the sample is taken. Samples from the early stage of the disease can give negative results, as seroconversion may not have occurred yet.
The average time for seroconversion of IgG in COVID-19 is ±14 days after the onset of symptoms and the probability of detecting specific IgG increases up to 99-100% within ±30 days. Similarly, not all antibodies appear at the same time and the antibody signature can be variable from one patient to another. Anti-nucleocapsids are often the first to appear while anti-RBD usually occur later. When the analysis is based on the criterion “the test is positive if at least 1 antibody is positive, whatever the antibody is“, the test sensitivity is significantly increased in the early phase of the disease, when compared to a mono-parametric assay.
Clinical Specificity
The specificity is a critical challenge in the interpretation of an assay for COVID-19. In this context, certain other human coronaviruses are antigenically related to SARS-CoV-2, and cross-reactivities are likely to occur, cfr SARS-CoV1, MERS-CoV, 229E, NL63, HKU1 and OC43.
The probability of a false positive result due to the presence of other HCoV cross-reactive antibodies depends on the antigen which is targeted. The nucleocapsid protein shares the most significant sequence homology between the coronaviruses, while RBD is the most variable antigenic domain. Therefore, an anti-Nucleocapsid test should be less specific than an RBD one. Specificity (n =118): 98.% (95% CI: 94.0%-99.8%)
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