Analytical performances of five SARS-CoV-2 whole-blood finger-stick IgG-IgM combined antibody rapid tests.

Facing the ongoing pandemic caused by SARS-CoV-2, there is an urgent need for serological assays identifying individuals previously infected by coronavirus disease 2019 (COVID-19), including rapid diagnostic tests (RDTs). We herein compared five new CE-IVD-labeled commercially available SARS-CoV-2 whole-blood finger-stick IgG/IgM combined RDTs, in parallel according to the manufacturers' instructions, with two serum panels obtained from 48 patients with confirmed COVID-19 (panel I) and from a group of 52 patients randomly selected, for whom serum samples collected before the COVID-19 epidemic (from October 1 to November 30, 2019) were negative for SARS-CoV-2 IgG (panel II). We found a sensitivity of 95.8 %, 91.6 %, 92.3 %, 97.9 % and 91.4 %, and a specificity of 98.1 %, 86.5 %, 100 %, 98.1 % and 84.6 %, for BIOSYNEX COVID-19 BSS (IgG/IgM) (Biosynex Swiss SA, Freiburg, Switzerland), Humasis COVID-19 IgG/IgM Test (Humasis Co., Ltd., Gyneonggi, Republic of Korea), LYHER COVID-19 IgM/IgG Rapid Test (Medakit Ltd, Hong Kong, China), SIENNA™ COVID-19 (IgG/IgM) Rapid Test Cassette (Salofa Oy, Salo, Finland) and NG-BIOTECH COVID-19 (IgG/IgM) (NG-Biotech, Guipry, France), respectively. Commercially available SARS-CoV-2 IgG/IgM combined RDTs have a sufficient sensitivity for identifying individuals with past SARS-CoV-2 infection, but some RDTs may lack of specificity, with risk of false positivity mainly for the IgM band.

Péré H ，Mboumba Bouassa RS ，Tonen-Wolyec S ，Podglajen I ，Veyer D ，Bélec L ... -  《-》

Unexpected high frequency of unspecific reactivities by testing pre-epidemic blood specimens from Europe and Africa with SARS-CoV-2 IgG-IgM antibody rapid tests points to IgM as the Achilles heel.

We aimed to evaluate the rates of false-positive test results of three rapid diagnostic tests (RDTs) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific immunoglobulin G (IgG) and IgM detection. Two serum panels from patients hospitalized in Paris, France, and from patients living in Bangui, Central African Republic, acquired before the 2019 COVID-19 outbreak, were tested by 3 CE IVD-labeled RDTs for SARS-CoV-2 serology (BIOSYNEX® COVID-19 BSS [IgG/IgM]; SIENNA™ COVID-19 IgG/IgM Rapid Test Cassette; NG-Test® IgG-IgM COVID-19). Detectable IgG or IgM reactivities could be observed in 31 (3.43%) of the 902 IgG and IgM bands of the 3 RDTs used with all pre-epidemic sera. The frequencies of IgG/IgM reactivities were similar for European (3.20%) and African (3.55%) sera. IgM reactivities were observed in 9 European and 14 African sera, while IgG reactivity was observed in only 1 African serum (15.1% vs. 0.66%). The test NG-Test® IgG-IgM COVID-19 showed the highest rates of IgG or IgM reactivities (6.12% [18/294]), while the test BIOSYNEX® COVID-19 BSS (IgG/IgM) showed the lowest rate (1.36% [4/294]). Some combinations of 2 RDTs in series allowed decreasing significantly the risk of false-positive test results. Our observations point to the risk of false-positive reactivities when using currently available RDT for SARS-CoV-2 serological screening, especially for the IgM band, even if the test is CE IVD-labeled and approved by national health authorities, and provide the rational basis for confirmatory testing by another RDT in case of positive initial screening.

Mboumba Bouassa RS ，Péré H ，Tonen-Wolyec S ，Longo JD ，Moussa S ，Mbopi-Keou FX ，Mossoro-Kpinde CD ，Grésenguet G ，Veyer D ，Bélec L ... -  《-》

Performance evaluation of two SARS-CoV-2 IgG/IgM rapid tests (Covid-Presto and NG-Test) and one IgG automated immunoassay (Abbott).

The aim of this study was to assess the analytical performances, sensitivity and specificity, of two rapid tests (Covid- Presto® test rapid Covid-19 IgG/IgM and NG-Test® IgM-IgG COVID-19) and one automated immunoassay (Abbott SARS-CoV-2 IgG) for detecting anti- SARS-CoV-2 antibodies. This study was performed with: (i) a positive panel constituted of 88 SARS-CoV-2 specimens collected from patients with a positive SARS-CoV-2 RT-PCR, and (ii) a negative panel of 120 serum samples, all collected before November 2019, including 64 samples with a cross-reactivity panel. Sensitivity of Covid-Presto® test for IgM and IgG was 78.4% and 92.0%, respectively. Sensitivity of NG-Test® for IgM and IgG was 96.6% and 94.9%, respectively. Sensitivity of Abbott IgG assay was 96.5% showing an excellent agreement with the two rapid tests (κ = 0.947 and κ = 0.936 for NGTest ® and Covid-Presto® test, respectively). An excellent agreement was also observed between the two rapid tests (κ = 0.937). Specificity for IgM was 100% and 86.5% for Covid-Presto® test and NG-Test®, respectively. Specificity for IgG was 92.0%, 94.9% and 96.5% for Covid-Presto®, NGTest ®, and Abbott, respectively. Most of the false positive results observed with NG-Test® resulted from samples containing malarial antibodies. In conclusion, performances of these 2 rapid tests are very good and comparable to those obtained with automated immunoassay, except for IgM specificity with the NG-Test®. Thus, isolated IgM should be cautiously interpreted due to the possible false-positive reactions with this test. Finally, before their large use, the rapid tests must be reliably evaluated with adequate and large panel including early seroconversion and possible cross-reactive samples.

Charpentier C ，Ichou H ，Damond F ，Bouvet E ，Chaix ML ，Ferré V ，Delaugerre C ，Mahjoub N ，Larrouy L ，Le Hingrat Q ，Visseaux B ，Mackiewicz V ，Descamps D ，Fidouh-Houhou N ... -  《-》

Clinical diagnostic performance evaluation of five immunoassays for antibodies to SARS-CoV-2 diagnosis in a real-life routine care setting.

While molecular techniques remain the gold standard for diagnosis of acute SARS-CoV-2 infection, serological tests have the unique potential to ascertain how much of the population has been exposed to the COVID-19 pathogen. There have been limited published studies to date documenting the performance of SARS-CoV-2 antibody assays in Nigeria and so we evaluated the diagnostic performance of five (5) immunoassay on a set of clinical samples. Five automated immunoassays (2019-nCoV IgG/IgM antibody determination kit, Tigsun COVID-19 combo IgM/IgG rapid test, rapid response COVID-19 IgG/IgM test, COVID-19 IgM-IgG combined antibody rapid test, iChroma COVID-19 Ab) were tested. Three hundred and fourteen specimens were analyzed from health care workers who tested positive PCR for SARS-CoV-2 with symptoms consistent with SARS-CoV-2 receiving treatment at two treatment centres in Nasarawa State from March to September, 2020 with control of 134 health care workers who tested negative PCR for SARS-CoV-2 with no symptoms to SARS-CoV-2. The median patients' age was 40 years (IQR 39.8-41), majority were male and were on admission. The SARS-CoV-2 IgG/IgM antibody evaluated kits had a sensitivity of 33% (2019-nCoV IgG/IgM antibody determination kit), 22% (Tigsun COVID-19 combo IgM/IgG rapid test), 43% (rapid response COVID-19 IgG/IgM test), 44% (COVID-19 IgM-IgG combined antibody rapid test), 25% (iChroma COVID-19 Ab), 100% sensitivity, accuracy of 68.5% and Kappa coefficient of 0.7 and rapid response COVID-19 IgG/IgM test cassette had a sensitivity of 33%, specificity of 100% and accuracy of 72.5% with Kappa coefficient 0.7. The Tigsun COVID-19 combo IgM/IgG rapid test (lateral flow), positive, COVID-19 IgM-IgG combined antibody rapid test and iChroma COVID-19 Ab RT all had sensitivity of zero percent. Serology was complementary to RT-PCR for the diagnosis of COVID-19 at least 14 days after onset of symptoms. The assay panel needs to be improved to serve as an option for the diagnosis of SARS-CoV-2 in resource constrained settings where there are limited molecular diagnostics testing panels.

Akyala AI ，Awayimbo JR ，Ogo AC ，Chima NJ ，Billyrose OMA ，Engom AOG ... -  《-》

Detection of SARS-CoV-2-specific antibodies via rapid diagnostic immunoassays in COVID-19 patients.

Chansaenroj J ，Yorsaeng R ，Posuwan N ，Puenpa J ，Sudhinaraset N ，Chirathaworn C ，Poovorawan Y ... -  《Virology Journal》