Basically, a lateral flow immunoassay is a simple diagnostic device used to confirm the presence or absence of a target analyte. It can test a variety of samples like urine, blood, saliva, sweat, serum, and other fluids. The LFIA is widely used in hospitals and clinical laboratories, as well as in veterinary medicine, in environmental assessment, and for safety testing during food production. The LFIA can be distinguished in two formats: direct and competitive. A direct test is used for larger analytes such as the p24 antigen used in the HIV test and analytes with multiple antigenic sites such as hCG used in pregnancy tests. A competitive test is used for small molecules with single antigenic determinants, which cannot bind to two antibodies simultaneously. Lateral flow assays have played a critical role in COVID-19 testing as they have the benefit of delivering a result in 15–30 minutes.