The Effect of Pooling on the Detection of the Nucleocapsid Protein of SARS-CoV-2 with Rapid Antigen Tests

Abstract

The COVID-19 pandemic puts significant stress on the viral testing capabilities of many countries. Rapid point-of-care (PoC) antigen tests are valuable tools but implementing frequent large scale testing is costly. We have developed an inexpensive device for pooling swabs, extracting specimens, and detecting viral antigens with a commercial lateral flow test for the nucleocapsid protein of SARS-CoV-2 as antigen. The holder of the device can be produced locally through 3D printing. The extraction and the elution can be performed with the entire set-up encapsulated in a transparent bag, minimizing the risk of infection for the operator. With 0.35 mL extraction buffer and six swabs, including a positive control swab, 43 ± 6% (n = 8) of the signal for an individual extraction of a positive control standard was obtained. Image analysis still showed a signal-to-noise ratio of approximately 2:1 at 32-fold dilution of the extract from a single positive control swab. The relative signal from the test line versus the control line was found to scale linearly upon dilution (R2 = 0.98), indicating that other pooling regimes are conceivable. A pilot project involving 14 participants and 18 pooled tests in a laboratory course at our university did not give any false positives, and an individual case study confirmed the ability to detect a SARS-CoV-2 infection with five-fold or six-fold pooling, including one swab from a PCR-confirmed COVID patient. These findings suggest that pooling can make frequent testing more affordable for schools, universities, and similar institutions, without decreasing sensitivity to an unacceptable level.

General overview on SARS-CoV-2 and potential role of natural compounds as antiviral drugs targeting SARS-CoV-2 proteins

“…Initially, testing was carried out with individual samples but when we repeatedly got negative results, we opted for pooling five samples into a 1.5 ml tube. Pooling of 5-fold to 20-fold swabs for RADT is already proved authentic by Berking et al (Berking et al, 2021) and Salcedo et al (Salcedo et al, 2021). All the currency samples were found negative by rapid antigen detection kit.…”

Optimal targeted mass screening in non‐uniform populations with multiple tests and schemes

“…Therefore, we set the value of $$$ N $$$ to 15 for PCR. On the other hand, the accuracy of LAT remains consistently high across group sizes ranging from 5 to 8, without any significant dilution effect (Berking et al, 2021; Stanley et al, 2022). Consequently, we set the value of $$$ N $$$ to 6 for LAT.…”

A Novel Rapid Test to Detect Anti-SARS-CoV-2 N Protein IgG Based on Shear Horizontal Surface Acoustic Wave (SH-SAW)

“…In addition, SARS-CoV-2 contains large amount of N protein. Moreover, the N protein is highly expressed during infection [7][8][9][10]. Currently, there are a number of methods to detect SARS-CoV-2, including viral culture, nucleic acid test, and immunoassay.…”