Key features and details
- Sample type: Cit plasma, Hep Plasma, Serum
- Detection method: Colorimetric
Product nameSARS-CoV-2 (COVID-19) IgA ELISA Kit
See all SARS-CoV-2 nucleocapsid protein kits
Intra-assay Sample n Mean SD CV% No. 1 24 5.19% No. 2 24 6.14% No. 3 24 10.56% Inter-assay Sample n Mean SD CV% No. 1 12 5.26% No. 2 12 4.8% No. 3 12 8.28%
Sample typeSerum, Hep Plasma, Cit plasma
Assay durationMultiple steps standard assay
SARS-CoV-2 (COVID-19) IgA ELISA Kit (ab277286) is intended for the qualitative determination of IgA class antibodies against SARS-CoV-2 in human serum or plasma (citrate, heparin) to support the diagnosis of COVID-19 disease and constitutes a supplement to direct pathogen detection. In addition, serology can be used to collect epidemiological information on the prevalence of SARS-CoV-2.
Microtiter plates are coated with specific antigens to bind corresponding antibodies of the sample. After washing the wells to remove all unbound sample material a horseradish peroxidase (HRP) labelled conjugate is added. This conjugate binds to the captured antibodies. In a second washing step unbound conjugate is removed. The immune complex formed by the bound conjugate is visualized by adding Tetramethylbenzidine (TMB) substrate which gives a blue reaction product. The intensity of this product is proportional to the amount of specific antibodies in the sample. Sulfuric acid is added to stop the reaction. This produces a yellow endpoint color. Absorbance at 450/620 nm is read using an ELISA Microtiter plate reader.
Antibody Isotypes and State of Infection:
Serology Significance IgM
Characteristic of the primary antibody response.
High IgM titer: → suggests a current or very recent infection.
Follows IgM production.
Characteristic of the secondary antibody response.
May persist for several years.
High IgG titer with low IgM titer: → may indicate past infection.
Produced in mucosal linings throughout the body (⇒ protective barrier).
Usually produced early in the course of the infection.
The diagnostic specificity is defined as the probability of the assay of scoring negative in the absence of the specific analyte. SARS-CoV-2 infections emerged in December 2019 in Wuhan, China. The expected prevalence values for German and US blood donor panels from before December 2019 therefore amount to 0 %. The determined positive results correspond to a specificity of 98.26 % (95 %-confidence interval: 93.86 % - 99.79 %).
Sample panel No. patients (n) Positive Equivocal Negative Specificity 95% CI Blood donors Germany 66 0 0 66 100% Blood donors US 50 2 1 47 95.92% Total 116 2 1 113 98.26% 93.86%-99.79%
The diagnostic sensitivity is defined as the probability of the assay of scoring positive in the presence of the specific analyte. 42 samples from 25 patients tested positive for SARS-CoV-2 RNA by RT-PCR were tested.
Days post symptom onset No. samples (n) Positive Equivocal Negative
Sensitivity (Eqv excluded)
0-5 13 1 0 12 7.69% 6-8 10 4 1 5 44.44% 9-11 10 4 1 5 44.44% greater than 12 9 8 1 0 100%
Three clinical samples exhibiting differing reactivities were tested for interference with each substance listed in the Table below: a positive, a negative, and an equivocal sample. All samples exhibited a change of signal less than 15 % when tested with each potential interferant.
Interferent Conc. tested Albumin 60 mg/mL Bilirubin conjugated 0.4 mg/mL Bilirubin unconugated 0.4 mg/mL Cholesterol 4 mg/mL Hemoglobin 10 mg/mL Triglycerides 15 mg/mL
105 samples with antibody activities to potentially cross reacting parameters (including antibodies to several respiratory pathogens) were tested to evaluate the cross reactivity of the assay.
Samples +ve to antibodies to No. of samples (n) Positive Equivocal Negative Adenovirus 10 0 1 9 Parainfluenzavirus 9 0 0 9 Candida albicans 8 0 0 8 Bordetella pertussis 9 0 0 9 Influenzavirus A 9 0 0 9 Influenzavirus B 10 0 1 9 Enterovirus 10 0 0 10 Respiratory syncytial virus 10 0 0 10 Chlamydia pneumoniae 9 0 0 9 Legionella pneumoniae 8 0 0 8 Mycoplasma pneumoniae 9 0 0 9 Haemophilus influenzae 3 0 0 3 Other Coronavirus 1 0 0 1
Cross reactions with antibodies to adenovirus and influenzavirus cannot be excluded. Cross reactivity with other human coronaviruses should be considered for result interpretation.
PlatformPre-coated microplate (12 x 8 well strips)
Storage instructionsStore at +4°C. Please refer to protocols.
Components 1 x 96 tests SARS-CoV-2 coated microplate 1 unit IgA Sample Dilution Buffer 1 x 100ml Stop Solution 1 x 15ml 20X Wash Buffer 1 x 50ml HRP-human IgA antibody 1 x 20ml TMB Substrate Solution 1 x 15ml Positive control 1 x 2ml Cut-off control 1 x 3ml Negative control 1 x 2ml
RelevanceNucleocapsid protein is a most abundant protein of coronavirus on the helical nucleocapsid of coronaviruses. N protein of SARS CoV-2 ab273530 is a structural protein required for RNA synthesis, and has RNA chaperone activity that may be involved in template switch. N protein enters the host cell with the viral RNA to facilitate its replication and process the virus particle assembly and release. N protein is a highly immunogenic phosphoprotein also implicated in modulating cell signalling pathways. Coronavirus nucleocapsid proteins localize to the cytoplasm and the nucleolus, a subnuclear structure, in both virus-infected primary cells and in cells transfected with plasmids that express N protein.
- 2019-nCoV nucleocapsid protein
Specific antigens are coated on the 96-well plate, controls or test samples are added to the well and incubated. The wells are washed to remove any unbound Human anti-antigen antibodies (Ig). A horseradish peroxidase (HRP) labelled anti-Human Ig conjugate is added to the wells. TMB is then catalyzed by the HRP to produce a blue color product that changes to yellow after adding an acidic stop solution. The intensity of yellow coloration is directly proportional to the amount of Human anti-antigen Ig captured on the plate.
ab277286 has not yet been referenced specifically in any publications.