A Lateral Flow Immunoassay Test Performance In Sars-Cov-2 Seroprevalence Surveys: A Validation Study Among Healthcare Workers

The objective of this study was to evaluate the validity and reliability of NG-Test (R) 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 (R) finger-prick test and collection of a blood sample on the same day. A second NG-Test (R) 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 (R) test was perfect (kappa coefficient = 100% [98%-100%]). The sensitivity of NG-Test (R) 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 (R) 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 (R) is used in seroprevalence surveys, we recommend that its diagnostic performance be taken into consideration to obtain a reliable estimation.