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 ... -  《-》

Development, performance evaluation, and clinical application of a Rapid SARS-CoV-2 IgM and IgG Test Kit based on automated fluorescence immunoassay.

The ongoing coronavirus disease 2019 (COVID-19) epidemic has made a huge impact on health, economies, and societies all over the world. Although reverse transcription-polymerase chain reaction (RT-PCR)-based nucleic acid detection has been primarily used in the diagnosis of COVID-19, it is time-consuming with limited application scenarios and must be operated by qualified personnel. Antibody test, particularly point-of-care antibody testing, is a suitable complement to nucleic acid test as it provides rapid, portable, and cost-effective detection of infections. In this study, a Rapid Antibody Test Kit was developed based on fluorescence immunochromatography for the sensitive, accurate, and automated detection of immunoglobulin M (IgM) and IgG antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in human serum, plasma, and whole blood samples within 10 min. The sensitivity, specificity, precision, and stability of the test kit were of good performance. No cross-activity and no interference was observed. In the multiple-center parallel study, 223 samples from hospitalized patients were used to evaluate the clinical specificity of the test. Both SARS-CoV-2 IgM and IgG achieved a clinical specificity of 98.21%. The clinical sensitivities of SARS-CoV-2 IgM and IgG were 79.54% and 87.45%, respectively, among 733 reverse transcription-polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 samples. For the combined IgM and IgG assays, the sensitivity and specificity were 89.22% and 96.86%, respectively. Our results demonstrate that the combined use of IgM and IgG could serve as a more suitable alternative detection method for patients with COVID-19, and the developed kit is of great public health significance for the prevention and control of the COVID-19 pandemic.

Kang K ，Huang L ，Ouyang C ，Du J ，Yang B ，Chi Y ，He S ，Ying L ，Chen G ，Wang J ... -  《-》

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 ... -  《-》

Assessment of SARS-CoV-2 serological tests for the diagnosis of COVID-19 through the evaluation of three immunoassays: Two automated immunoassays (Euroimmun and Abbott) and one rapid lateral flow immunoassay (NG Biotech).

The emergence of new SARS-CoV-2 has promoted the development of new serological tests that could be complementary to RT-PCR. Nevertheless, the assessment of clinical performances of available tests is urgently required as their use has just been initiated for diagnose. The aim of this study was to assess the performance of three immunoassays for the detection of SARS-CoV-2 antibodies. Two automated immunoassays (Abbott SARS-CoV-2 CLIA IgG and Euroimmun Anti-SARS-CoV-2 ELISA IgG/IgA assays) and one lateral flow immunoassay (LFIA NG-Test® IgG-IgM COVID-19) were tested. 293 specimens were analyzed from patients with a positive RT-PCR response, from patients with symptoms consistent with COVID-19 but exhibiting a negative response to the RT-PCR detection test, and from control group specimens. Days since symptoms onset were collected from clinical information sheet associated with respiratory tract samples. Overall sensitivity for IgG was equivalent (around 80 %) for CLIA, ELISA and LFIA. Sensitivity for IgG detection, >14 days after onset of symptoms, was 100.0 % for all assays. Overall specificity for IgG was greater for CLIA and LFIA (more than 98 %) compared to ELISA (95.8 %). Specificity was significantly different between IgA ELISA (78.9 %) and IgM LFIA (95.8 %) (p < 0.05). The best agreement was observed between CLIA and LFIA assays (97 %; k = 0.936). Excellent sensitivity for IgG detection was obtained >14 days after onset of symptoms for all immunoassays. Specificity was also excellent for IgG CLIA and IgG LFIA. Our study shows that NG-Test® is reliable and accurate for routine use in clinical laboratories.

Nicol T ，Lefeuvre C ，Serri O ，Pivert A ，Joubaud F ，Dubée V ，Kouatchet A ，Ducancelle A ，Lunel-Fabiani F ，Le Guillou-Guillemette H ... -  《-》

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 ... -  《-》