Colloidal gold immunochromatographic assay (GICA) is an effective screening method for identifying detectable anti-SARS-CoV-2 neutralizing antibodies

Li, Xinjie; Yin, Yue; Pang, Ling; Xu, Shuyun; Lu, Fengmin; Xu, Dong; Shen, Tao

Introduction A large number of COVID-19 patients are in recovery and millions of people are vaccinated COVID-19 vaccines globally daily. This calls for a rapid screening strategy of SARS-CoV-2 protective antibodies generated in rehabilitators and vaccinated populations. Methods Serum samples collected over a follow-up period of 6 months from 306 COVID-19 cases discharged from Wuhan Tongji Hospital were analyzed. Anti-S Abs were detected by colloidal gold immunochromatographic assay (GICA) and neutralizing antibodies (nAbs) were detected by chemiluminescent microparticle immunoassay (CMIA). Results Most COVID-19 survivors tested positive for anti-S Abs (83.7%) and nAbs (98.0%) 6 months after being discharged from the hospital, and the levels of anti-S Abs in the blood were highly positively correlated with nAbs (r = 0.652, P < 0.0001). The positivity rate of nAbs for patients with anti-S Abs positive was 100%. Conclusions There is a good agreement between anti-S Abs detected by GICA and nAbs detected by CMIA. It indicates that anti-S Abs detected by GICA may be used as a cheaper screening strategy for detectable SARS-CoV-2 nAbs in COVID-19 convalescent individuals.