Methods and techniques are described for analyzing test fluids to determine presence, absence, or concentration of analytes in the test fluids. The methods may correspond to diagnostic testing, such as quickly (within 5 minutes) identifying whether or not an individual may have a particular disease or condition, such as infection by SARS-CoV-2 or a SARS-CoV-2 variant or vaccine-induced immunity or natural immunity to infection by SARS-CoV-2 or a SARS-CoV-2 variant, or whether an individual would benefit from a vaccine booster. The test results can be used for a variety of applications including facilitating or controlling access at events, venues, or transportation systems, or generating exposure notifications.