Publications & Posters

Quantifying SARS-CoV-2 nucleocapsid antigen in oropharyngeal swabs using single molecule array technology

Scientific Reports | October 13, 2021

Olsen DA, Brasen CL, Kahns S, Madsen JB, Kierkegaard H, Christensen H, Jensen A, Sydenham TV, Møller JK, Madsen JS and Brandslund I

Sci Rep. 2021;11:20323

This study was performed using the Quanterix HD-1 Analyzer.

This study was performed using Simoa Homebrew assay(s).


This study aimed to develop a highly sensitive SARS-CoV-2 nucleocapsid antigen assay using the single molecule array (Simoa) technology and compare it with real time RT-PCR as used in routine clinical practice with the ambition to achieve a comparative technical and clinical sensitivity. Samples were available from 148 SARS-CoV-2 real time RT-PCR positive and 73 SARS-CoV-2 real time RT-PCR negative oropharyngeal swabs. For determination of technical sensitivity SARS-CoV-2 virus culture material was used. The samples were treated with lysis buffer and analyzed using both an in-house and a pre-commercial SARS-CoV-2 nucleocapsid antigen assay on Simoa. Both nucleocapsid antigen assays have a technical sensitivity corresponding to around 100 SARS-CoV-2 RNA molecules/mL. Using a cut-off at 0.1 pg/mL the pre-commercial SARS-CoV-2 nucleocapsid antigen assay had a sensitivity of 96% (95% CI 91.4–98.5%) and specificity of 100% (95% CI 95.1–100%). In comparison the in-house nucleocapsid antigen assay had sensitivity of 95% (95% CI 89.3–98.1%) and a specificity of 100% (95% CI 95.1–100%) using a cut-off at 0.01 pg/mL. The two SARS-CoV-2 nucleocapsid antigen assays correlated with r = 0.91 (P < 0.0001). The in-house and the pre-commercial SARS-CoV-2 nucleocapsid antigen assay demonstrated technical and clinical sensitivity comparable to real-time RT-PCR methods for identifying SARS-CoV-2 infected patients and thus can be used clinically as well as serve as a reference method for antigen Point of Care Testing.