Two rapid SARS-CoV-2 disposable devices for semi-quantitative S-RBD antibody levels determination compared with CLIA and ELISA assays at different protective thresholds

• Published in: Clinica chimica acta Vol. 529; pp. 104 - 108
• Main Authors: Padoan, Andrea, Cosma, Chiara, Galla, Luisa, Basso, Daniela, Plebani, Mario
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-04-2022
• Subjects: Antibodies; Antibodies, Viral; BNT162 Vaccine; CLIA; COVID-19 - diagnosis; ELISA; Enzyme-Linked Immunosorbent Assay; Female; Health Personnel; Humans; iRapid; Male; Middle Aged; Point of care device; Protective thresholds; Rapid antibody test; SARS-CoV-2; SARS-CoV-2; Antibodies; Protective thresholds; Rapid antibody test; Point of care device; iRapid; CLIA; ELISA
• ISSN: 0009-8981; 1873-3492
• DOI: 10.1016/j.cca.2022.02.014

•Timely, cost-effective determination of SARS-CoV-2 Ab could help pandemic migration.•iRapid self-test and professional measure neutralizing Ab in a semi-quantitative scale.•Both iRapid had good overall agreements of 95.1% and 95.9% for detecting minimum protection thresholds.•iRapid performances differ on the basis of the comparative reference assay.
Performance of two disposable devices for identifying subjects with low anti-SARS-CoV-2 protection was compared with that of automated enzyme-linked immunosorbent (ELISA) and chemiluminescent (CLIA) assay.
In July 2021, 123 healthcare workers (HCW), twice vaccinated by BNT162b2/Comirnaty mRNA (BioNTech-Pfizer), underwent Ab iRapid COVID-19 Quant “Neutralizing” Self-test (iRapid Self-test) and “Neutralizing” Professional-use (iRapid pro) (DIESSE, Diagnostica Senese, Siena, Italy). Simultaneously, serum Ab were determined by Maglumi 2000 plus (anti S-RBD CLIA assay, Snibe Diagnostics, Shenzhen, China) and SARS-CoV-2 “Neutralizing” Ab Chorus ELISA (DIESSE, Siena, Italy). Results were evaluated against two “protective-thresholds”, 90 kBAU/L and 506 kBAU/L.
HCW mean age, 46.2 (±12.6) years; 26 (20.5%), males, 101 (79.5%), females. The mean time interval (and standard deviation) between the first vaccine dose and Ab determination was 129.5 (±36.4) days and was neither gender (p = 0.879) nor age (p = 0.341) related. With Maglumi, 114 (89.7%) and 43 (33.8%) HCW presented Ab ≥ 90 kBAU/L and Ab ≥ 506 kBAU/L, respectively; with Chorus, 96 (75.6%) presented Ab values ≥506 kBAU/L. CLIA and ELISA agreement was 56.7%. At 90 kBAU/L, iRapid self-test and Pro sensitivities were 98.2% (95% CI: 92.7–99.8), specificity 69.2% (95% CI: 38.6–90.9%) and 76.9% (46.2–95%), respectively. At 506 kBAU/L, iRapid sensitivities were 58.1–91.6%, and specificities, 89–96.6%. On evaluating Ab at <4 and ≥4 months, protective titers had decreased.
iRapid semi-quantitative devices had very good overall agreements of 95.1% and 95.9% for detecting individuals with low anti-SARS-CoV-2 protection.