Table 4. Description of serological tests in close contact studies of SARS-CoV-2.
| Study ID | Serological test | Description of test | Thresholds for serological positivity |
|---|---|---|---|
| Agergaard 2020 | IgG and IgM | iFlash and DiaSorin | iFlash SARS-CoV-2 N/S IgM/IgG cut-off: ≥12 AU/ml = positive.
DiaSorin SARS-CoV-2 S1/S2 IgG cut-off: ≥15 AU/ml = positive, 12 < x < 15 AU/ml = equivocal, and ≤12 AU/ml = negative. |
| Angulo-Bazán 2020 | IgG and IgM | Coretests ® COVID-19 IgM / IgG Ab Test (Core Technology Co. Ltd), a lateral flow immunochromatographic test that qualitatively
detects the presence of antibodies against SARS-CoV-2, with a sensitivity and specificity reported by the manufacturer for IgM / IgG of 97.6% and 100%, respectively |
Not reported |
| Armann 2020 | IgG | Diasorin LIAISON® SARS-CoV-2 S1/S2 IgG Assay). All samples with a positive or equivocal LIAISON® test result, as well as all samples
from participants with a reported personal or household history of a SARS-CoV-2 infection, were re-tested with two additional serological tests: These were a chemiluminescent microparticle immunoassay (CMIA) intended for the qualitative detection of IgG antibodies to the nucleocapsid protein of SARS-CoV-2 (Abbott Diagnostics® ARCHITECT SARS-CoV-2 IgG ) (an index (S/C) of < 1.4 was considered negative whereas one >/= 1.4 was considered positive) and an ELISA detecting IgG against the S1 domain of the SARS- CoV-2 spike protein (Euroimmun® Anti-SARS-CoV-2 ELISA) (a ratio < 0.8 was considered negative, 0.8–1.1 equivocal, > 1.1 positive) Participants whose positive or equivocal LIAISON® test result could be confirmed by a positive test result in at least one additional serological test were considered having antibodies against SARS-CoV_x0002_2. |
Antibody levels > 15.0 AU/ml were considered positive and levels
between 12.0 and 15.0 AU/ml were considered equivocal. |
| Baettig 2020 | IgG and IgM | Used commercially available immunochromatography rapid test with SARS-CoV-2 protein-specific IgM and IgG. This test was
performed according to the manufacturers’ instructions with a reported sensitivity and specificity of 93% and 95%, respectively. |
Not reported |
| Basso 2020 | IgG and IgM | Sera were collected approximately 3 weeks following exposure for the detection of antibodies against SARS-CoV-2. EDI Novel
Coronavirus COVID-19 lgG and IgM ELISA (Epitope Diagnostics, Inc., San Diego, CA, USA) were used for initial testing, and supplemented with tests from DiaSorin (LIAISON SARS-CoV-2 S1/S2 IgG test), Abbott (Alinity i SARS-CoV-2 IgG), Roche (Elecsys Anti- SARS-CoV-2) and Wantai (WANTAI SARS-CoV-2 Ab ELISA). |
Not reported |
| Brown 2020 | IgG and IgM | ELISA (authors referenced another study) | Reciprocal titers of >400 to be positive and reciprocal titers of
>100 but <400 to be indeterminate. |
| Chen 2020b | IgG and IgM | In-house enzyme immunoassay (EIA). 96-well plates were coated with 500 ng/mL of recombinant RBD or NP protein overnight,
incubating with diluted serum samples at 1:20. Plates were incubated with either anti-human IgM or IgG conjugated with HRP. Optical density (OD) value (450nm-620nm) was measured. |
Preliminary cut-off values were calculated as the mean of the
negative serum OD values plus 3 standard deviation (SD) from 90 archived healthy individuals in 2019. A close contact was considered seropositive if OD of 1:20 diluted serum was above the cut-off values for either IgM or IgG against both RBD and NP protein |
| Chu 2020 | IgG and IgM | Serum samples were tested at CDC using a SARS-CoV-2 ELISA with a recombinant SARS-CoV-2 spike protein (courtesy of Dr. Barney
Graham, National Institutes of Health, Bethesda, MD, USA) as an antigen. Protein ELISA 96-well plates were coated with 0.15 μg/mL of recombinant SARS-CoV-2 spike protein and ELISA was carried out as previously described. An optimal cutoff optical density value of 0.4 was determined for >99% specificity and 96% sensitivity. Serum samples from the case-patient were used as a positive control and commercially available serum collected before January 2020 from an uninfected person as a negative control. |
Total SARS-CoV-2 antibody titers >400 were considered
seropositive. |
| Dattner 2020 | IgG | Abbott SARS-CoV-2 IgG, whose specificity was estimated as ∼100% and whose sensitivity at ≥ 21 days was estimated as ∼85% | Not reported |
| de Brito 2020 | IgG and IgM | Chemiluminescence 4 weeks after contact with the index case | Not reported |
| Dimcheff 2020 | IgG | Serum IgG to thD4:D12e nucleoprotein of SARS-CoV-2 was measured using a Federal Food and Drug Administration (FDA)
emergency-use–authorized chemiluminescent microparticle immunoassay performed on an automated high throughput chemistry immunoanalyzer (Architect i2000SR, Abbott Laboratories, Abbott Park, IL). The sensitivity of this assay is reported to be 100% with a specificity of 99% at >14 days after symptom onset in those infected with SARS-CoV-2.1 At 5% prevalence, the positive predictive value is 93.4% and the negative predictive value is 100% |
Results are reported in a relative light units (RLU) index; a value
≥1.4 RLU is considered a positive antibody response. |
| Dub 2020 | IgG | IgG antibodies to SARS-CoV-2 nucleoprotein (The Native Antigen Company, United Kingdom) were measured
with a fluorescent bead-based immunoassay (manuscript in preparation). Antigen was conjugated on MagPlex Microspheres and bound IgG antibodies were identified by a fluorescently labeled conjugated antibody (R_x0002_Phycoerythrin- conjugated Goat Anti-Human IgG, Jackson Immuno Research, USA). The plate was read on Luminex® MAGPIX® system. xPONENT software version 4.2 (Luminex®Corporation, Austin, TX) was used to acquire and analyze data. Median fluorescent intensity was converted to U/ml by interpolation from a 5- parameter logistic standard curve. The specificity and sensitivity of the assay was assessed using receiver operator curve (ROC) with 100% specificity and 97.9% sensitivity |
MNT titre of ≥ 6 considered positive
FMIA titre 3·4 U/ml considered positive |
| Fontanet 2020 | IgG | Antibody responses to SARS-CoV-2 using several assays developed by Institut Pasteur : an ELISA N assay, detecting antibodies
binding to the N protein; a S-Flow assay, which is a flow-cytometry based assay detecting anti-S IgG; and a LIPS assay, which is an immunoprecipitation-based assay detecting anti-N and anti-S1 IgG. |
Participants were considered seropositive for SARS-CoV-2 if any
test was positive, since all tests had a specificity higher than 99% with the cut-offs chosen for positivity |
| Fontanet 2020a | Not specified | Serological testing was conducted using the S-Flow assay, a flow_x0002_cytometry-based serological test developed by the Institut
Pasteur. The assay is based on the recognition of the SARS-CoV-2 Spike protein expressed at the surface of 293T cells. In previous studies, the sensitivity of the assay was estimated at 99.4% (95% CI = 96.6% - 100%) on a panel of 160 RT-PCR confirmed mild forms of COVID-1928, while its specificity was found to be 100% (one-sided 97.5% CI = 97.4% - 100%) on a panel of 140 pre-epidemic sera |
Not reported |
| Gu 2020 | IgG | Not described | Not reported |
| Helsingen 2020 | IgG | Measurement of IgG antibodies was performed with a multiplex flow cytometric assay known as microsphere affinity proteomics
(MAP) |
Not specified. Referenced |
| Hong 2020 | IgG and IgM | Qualitative colloidal gold assay (Innovita (Tangshan) Biological Technology, Co., Ltd, Tangshan, China), following manufacturers’
instructions. The sensitivity of the assay was 87.3% (95%CI 80.4–92.0%), and the specificity was 100% (95%CI 94.20–100%) according to the instructions of the assay. |
Not reported |
| Kuwelker 2020 | IgG | A two-step ELISA was used for detecting SARS-CoV-2-specific antibodies, initially by screening with receptor-binding domain (RBD)
and then confirming seropositivity by spike IgG. Endpoint titres were calculated as the reciprocal of the serum dilution giving an optical density (OD) value=3 standard deviations above the mean of historical pre-pandemic serum samples. Individuals with no antibodies were assigned a titre of 50 for calculation purposes. Neutralisation assays were used to quantify SARS-CoV-2-specific functional antibodies. VN titres were determined as the reciprocal of the highest serum dilution giving no CPE. Negative titres (<20) were assigned a value of 10 for calculation purpose. |
Not specified. |
| Lewis 2020 | Not specified | ELISA (authors referenced another study) | Not specified |
| Luo 2020a | IgG and IgM | Not described | Asymptomatic: Specific IgM detected in serum.
Symptomatic: Detectable SARS-CoV-2–specific IgM and IgG in serum, or at least a 4-fold increase in IgG between paired acute and convalescent sera. |
| Macartney 2020 | IgA, IgG, IgM | SARS-CoV-2-specific IgG, IgA, and IgM detection was done using an indirect immunofluorescence assay (IFA) that has a sensitivity
compared with nucleic acid testing of detecting any of SARS-CoV-2-specific IgG, IgA, or IgM when samples were collected at least 14 days after illness onset of 91·3% (95% CI 84·9–95·6) and specificity of 98·9% (95% CI 98·4–99·3%; MVNO, personal communication). |
Not specified |
| Martinez-Fierro 2020 | IgG and IgM | IgM and IgG against SARS-CoV-2 were determined using a total blood sample through a 2019 nCov IgG/IgM rapid test (Genrui
Biotech, Shenzen, China) |
Not specified |
| Ng 2020 | Not specified | human ACE-2 (hACE2) protein (Genscript Biotech, New Jersey, United States) was coated at 100 ng/well in 100 mM carbonate-
bicarbonate coating buffer (pH 9.6). 3ng of horseradish peroxidase (HRP)-conjugated recombinant receptor binding domain (RBD) from the spike protein of SARS-CoV-2 (GenScript Biotech) was pre-incubated with test serum at the final dilution of 1:20 for 1 hour at 37°C, followed by hACE2 incubation for 1 h at room temperature.Serum samples were tested with a surrogate viral neutralising assay for detection of neutralising antibodies to SARS-CoV-2. |
A positive serological test result was concluded if the surrogate
viral neutralising assay for a particular sample resulted in inhibition of 30% or greater (98·9% sensitivity and 100·0% specificity) |
| Ogawa 2020 | IgG | Abbott® (Abbott ARCHITECT SARS-CoV-2 IgG test, Illinois, USA) | Not specified |
| Poletti 2020 | IgG | Not described | Not specified |
| Razvi 2020 | IgG and IgM | Blood samples were analysed on the day of collection using the Roche Elecsys Anti-Sars-CoV-2 serology assay. This
electrochemiluminescent immunoassay is designed to detect both IgM and IgG antibodies to SARS-CoV-2 in human serum and plasma and has been shown to have a high sensitivity and specificity |
Not specified |
| Schumacher 2020 | IgG and IgM | SARS-CoV-2-specific antibodies were measured in serum samples using an
electrochemiluminescence immunoassay (Elecsys® Anti-SARS-CoV-2, Roche Diagnostics, Rotkreuz, Switzerland). |
Cut-off indices ≤1 reported as negative and indices >1 as positive. |
| Torres 2020 | IgG and IgM | Novel Coronavirus (2019-nCoV) IgG/IgM Test Kit (Colloidal gold) from Genrui Biotech Inc. The study nurse and/or technician viewed
the photo provided by the participant along with the participant’s self-report as to the visibility of the three bands, and determined whether the tests were IgG+, IgM+, IgG & IgM+, Negative, Invalid, or Indeterminate. Participants were asked to attach a photo of the test after 15 minutes had elapsed and self-report the appearance of the three lines, G (IgG), M (IgM), and C (test control) |
Colour-coded - self-administered test: self-reporting the
appearance of the three lines, G (IgG), M (IgM), and C (test control) |
| van der Hoek 2020 | IgG | Fluorescent bead-based multiplex-immunoassay. Referenced | A cut-off concentration for seropositivity (2.37 AU/mL; with
specificity of 99% and sensitivity of 84.4%) was determined by ROC-analysis of 400 pre-pandemic control samples |
| Wendt 2020 | IgA and IgG | ELISA (Euroimmun, Lübeck, Germany), following the manufacturer’s instructions. | Inconclusive (≥0.8 and <1.1) or Positive (≥1.1 |
| Yang 2020 | IgA, IgG, IgM | Serum immunoglobulin (Ig) antibody against the SARS-CoV-2 surface spike protein receptor-binding domain (RBD) was measured
using a chemiluminescence kit (IgM, IgG, and total antibody, Beijing Wantai Biotech, measured by cut-off index [COI]) or ELISA kit (IgA, Beijing Hotgen Biotech, measured by optical density at 450/630 nm [OD450/630]). The cut-off for seropositivity was set according to the manufacturer’s instruction, verified using positive (169 serum specimens from confirmed COVID-19 patients) and negative (128 serum specimens from healthy persons) controls, and both of sensitivity and specificity were 100%. Virus neutralization assays were performed using SARS-CoV-2 virus strain 20SF014/vero-E6/3 (GISAID accession number EPI_ISL_403934) in biosafety level 3 (BSL-3) laboratories. Neutralizing antibody (NAb) titer was the highest dilution with 50% inhibition of cytopathic effect, and a NAb titer of ≥1:4 was considered positive. |
Specimens with COI>1 (IgM, IgG, or total antibody),
OD450/630 > 0.3 (IgA) were considered positive. |
| Zhang 2020b | IgG and IgM | SARS-CoV-2-specific IgM and IgG were tested by paramagnetic particle chemiluminescent immunoassay using iFlash-SARS-CoV-2
IgM/IgG assay kit (Shenzhen YHLO Biotech Co., Ltd) and iFlash Immunoassay Analyzer (Shenzhen YHLO Biotech Co., Ltd). The specificity and sensitivity of SARS-CoV-2 IgM and IgG detection were also evaluated |
Not specified |