Журнал аналитических и биоаналитических методов

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Development of a Saliva-based Lateral Flow Assay for SARS-CoV-2 with the potential to quantify viral load

Chetan Shende, Duncan Farquharson, Stuart Farquharson

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the deadliest virus in the last 50 years, with the USA having the highest reported deaths and cases at over 1.1 million and over 100 million, respectively, as of June 1, 2023. Identifying infected people remains the primary method of stopping the spread of the virus, either using real-time, quantitative polymerase chain reaction instruments or at-home lateral flow assay (LFA) antigen tests. Herein we describe a simple four step at-home SARS-CoV-2 LFA test that provides three advantages over current LFAs. The test employs 1) saliva sampling, 2) three antibodies to bind the virus to the LFA Test Line, and 3) a smartphone to quantify the reflectance of the Test Line in terms of Ct values. The use of saliva samples eliminates the pain and fear of nasopharyngeal sampling, especially for children. The use of three antibodies yielded 100% correct sensitivity, specificity, predicted positive and predicted negative for samples with Ct values of 29 and below. The use of a smartphone to measure reflectance allowed calculating the Ct values for 16 samples with an average error and standard deviation of 0.58±0.43 for samples with Ct values below 26. The smartphone also adds the capability of sharing the results to track and slow the spread of the virus. The combination lateral flow assay and smartphone quantitation is well suited for identifying, quantifying, and slowing the spread of future viruses.