Development of an antigen agglutination test for rapid screening of COVID-19 in low laboratory capacity and field settings

Abstract

The transition of COVID-19 from a pandemic to a general disease has highlighted the need for affordable and accessible diagnostic tests to control the spread of SARS-CoV-2. While PCR tests have been the gold standard for detecting the virus, they are costly and require laboratory facilities, making their accessibility difficult in low-resource settings. Rapid Diagnostic Tests (RDTs), such as SD Biosensor Standard Q and Abbot PanBio, are a more affordable option, but they are still expensive, especially in Uganda, where the country relies on imports. This strain on the healthcare system emphasizes the need to develop local solutions for COVID-19 testing. One promising approach is latex agglutination, a simple, low-cost method used to detect antigens in patient samples. Latex agglutination tests are fast, easy to perform, and require no specialized equipment—only a white tile or cardboard and a light source for night testing. This makes them ideal for use in low-resource settings, even at the most basic healthcare levels (such as Health Center II or private clinics). Results: Using a commercial latex bead conjugation kit, and commercially sourced anti- SARS-CoV-2 antibody from abcam biosciences, and with the instructions in the manufacturer’s manual, we successfully developed the Latex bead Conjugate reagent for use in a SARS-CoV-2 Latex Bead antigen agglutination test kit.The combination of 25µL of the developed Latex Beads/Antibody Conjugate reagent to 13µL of nasopharyngeal sample suspension was selected as the combination of choice for the test. Out of the 20 nasopharyngeal samples tested, 7 tested positive, while 13 testes negative and the sensitivity was 54% while the specificity of 100%. Conclusion: The latex agglutination assay was developed and it had a relatively low sensitivity of 54% but excellent on specificity of 100%. Low sensitivity seemed to stem from the poor performance of the Latex Agglutination Test among samples with a real-time PCR threshold cycle (Ct) value of >33.