Evaluation of antibody testing for SARS-Cov-2 using ELISA and lateral flow immunoassays

Adams, Emily R; Anand, Rekha; Andersson, Monique I; Auckland, Kathryn; Baillie, J Kenneth; Barnes, Eleanor; Bell, John; Berry, Tamsin; Bibi, Sagida; Carroll, Miles; Chinnakannan, Senthil; Clutterbuck, Elizabeth; Cornall, Richard J; Crook, Derrick W; De Silva, Thushan; Dejnirattisai, Wanwisa; Dingle, Kate E; Dold, Christina; Eyre, David W; Farmer, Helen; Hoosdally, Sarah J; Hunter, Alistair; Jeffrey, Katie; Klenerman, Paul; Knight, Julian; Knowles, Clarice; Kwok, Andrew J; Leuschner, Ullrich; Liu, Chang; Lopez-Camacho, Cesar; Matthews, Philippa C; McGivern, Hannah; Mentzer, Alexander J; Milton, Jonathan; Mongkolsapaya, Juthathip; Moore, Shona C; Oliveira, Marta S; Pereira, Fiona; Peto, Timothy; Ploeg, Rutger J; Pollard, Andrew; Prince, Tessa; Roberts, David J; Rudkin, Justine K; Screaton, Gavin R; Semple, Malcolm G; Skelly, Donal T; Smith, Elliot Nathan; Staves, Julie; Stuart, David; Supasa, Piyada; Surik, Tomas; Tsang, Pat; Turtle, Lance; Walker, A Sarah; Wang, Beibei; Washington, Charlotte; Watkins, Nicholas; Whitehouse, James; Beer, Sally; Levin, Robert; Espinosa, Alexis; Georgiou, Dominique; Martinez Garrido, Jose Carlos; Thraves, Hannah; Perez Lopez, Elena; del Rocio Fernandez Mendoza, Maria; Sobrino Diaz, Alberto Jose; Sanchez, Veronica

Background: The SARS-CoV-2 pandemic caused >1 million infections during January-March 2020. There is an urgent need for robust antibody detection approaches to support diagnostics, vaccine development, safe individual release from quarantine and population lock-down exit strategies. The early promise of lateral flow immunoassay (LFIA) devices has been questioned following concerns about sensitivity and specificity. Methods: We used a panel of plasma samples designated SARS-CoV-2 positive (from SARS-CoV-2 RT-PCR-positive individuals; n=40) and negative (samples banked in the UK prior to December-2019 (n=142)). We tested plasma for SARS-Cov-2 IgM and IgG antibodies by ELISA and using nine different commercially available LFIA devices. Results: ELISA detected SARS-CoV-2 IgM or IgG in 34/40 individuals with an RT-PCR-confirmed diagnosis of SARS-CoV-2 infection (sensitivity 85%, 95%CI 70-94%), vs 0/50 pre-pandemic controls (specificity 100% [95%CI 93-100%]). IgG levels were detected in 31/31 RT-PCR-positive individuals tested ≥10 days after symptom onset (sensitivity 100%, 95%CI 89-100%). IgG titres rose during the 3 weeks post symptom onset and began to fall by 8 weeks, but remained above the detection threshold. Point estimates for the sensitivity of LFIA devices ranged from 55-70% versus RT-PCR and 65-85% versus ELISA, with specificity 95-100% and 93-100% respectively. Within the limits of the study size, the performance of most LFIA devices was similar. Conclusions: The performance of current LFIA devices is inadequate for most individual patient applications. ELISA can be calibrated to be specific for detecting and quantifying SARS-CoV-2 IgM and IgG and is highly sensitive for IgG from 10 days following symptoms onset.