A lateral flow immunoassay test performance in SARS-CoV-2 seroprevalence surveys: a validation study among healthcare workers

Abstract

The objective of this study was to evaluate the validity and reliability of NG-Test® when used as a finger-prick test on healthcare workers and to compare it to the ELISA Wantai Immunoassay. Fifty-one healthcare workers who were RT-PCR SARS-CoV-2 positive and 59 who were RT-PCR SARS-CoV-2 negative accepted to participate in this study. They were subjected to an NG-Test® finger-prick test and collection of a blood sample on the same day. A second NG-Test® on another finger was performed for the first 30 cases and controls and read blinded to the first. Sera obtained from blood samples were used to perform the Wantai SARS-CoV-2 ELISA. The interobserver agreement for the NG-Test® test was perfect (kappa coefficient = 100% [98%–100%]). The sensitivity of NG-Test® was estimated to be 85% [71.9%–92.3%] and the specificity 98.3% [95.0%–100.0%]) for both IgG and IgM. The percentage of agreement between the Wantai immunoassay and NG-Test® was 92.73% for IgG (Kappa = 0.85 [0.75–0.95]) and 65.45% (Kappa = 0.42 [0.26–0.58]) for IgM. Our study highlights the need to validate rapid immunoassay tests under real-life conditions. If NG-Test® is used in seroprevalence surveys, we recommend that its diagnostic performance be taken into consideration to obtain a reliable estimation.

COVID-19 Antibody Detecting Rapid Diagnostic Tests Show High Cross-Reactivity When Challenged with Pre-Pandemic Malaria, Schistosomiasis and Dengue Samples

“…IgM test lines accounted for more than two-thirds (67.9%) of cross-reacting test lines. False-positive IgM test lines in COVID-19 Ab RDTs have been reported before [ 18 , 42 , 51 ], and given the comparable kinetics of IgM and IgG, selective testing for IgM has been questioned [ 52 ]. In that regard, a seroprevalence study in Spain took into account only the IgG results of the COVID-19 Ab RDT used, while disregarding the IgM results [ 53 ].…”

Role of non-aerosols activities in the transmission of SARS-Cov-2 infection among health care workers

“…Our validation study 12 demonstrated that SARS-CoV-2 serological test with LFIAT had a predictive positive value of 49.7% and a negative predictive value of 99.7% in our population study for IgG. We thus determined the SARS-CoV-2 serological status (negative / positive) using two distinct approaches.…”

“…Our study also has several strengths. The determination of SARS-CoV-2 status was based on a LFIA test that we previously validated 12 . Our knowledge of the quality of both the negative and positive predictive values allowed us to include these data in our models, using multiple imputation after stratification on the LFIA test response.…”

“…After completion of the questionnaire, all HCWs underwent a SARS-CoV-2 Lateral Flow ImmunoAssay Test (LFIAT), namely the NG-Test® finger-prick test 11 , with a reading 20 min after the prick by trained nurses or doctors. This test allows the detection of anti-SARS-CoV-2 IgG with a sensitivity of 82.5% and a specificity of 98% 12 . If the LFIAT was positive, a venous blood sample (7 mL) was drawn to confirm the serological status (Wantai SARS-CoV-2 Ab ELISA, Beijing, China).…”

Risk factors for SARS-CoV-2 infection among health care workers

“…IgG with a sensitivity of 82.5% and a specificity of 98%. 13 If the LFIAT was positive, a venous blood sample (7 mL) was proposed to confirm the serological status (Wantai SARS-CoV-2 Ab ELISA, Beijing, China).…”