evidence: Clinicians and patients always want to know they can trust the accuracy of lab test results. This has never been more true than it is now, given the attention on COVID-19 testing and its role in helping to halt the spread of COVID-19. This article explains what we know so far about both nucleic acid tests and antibody detection tests for the SARS-CoV-2 virus, and what factors can affect the reliability of an individual test result. As with all lab tests, a number of factors determine the accuracy of a COVID-19 test result. These include not only the instrument and chemical reagents used to perform the test, but also the timing and quality of specimen collection and the biology of the individual patient. [...] There are two main types of tests for COVID-19. The first detects viral RNA using molecular methods such as polymerase chain reaction (PCR). You can read more about this test in ARUP Consult’s COVID-19 topic. These tests are highly specific because they are based on the unique genetic sequence of SARS-CoV-2. If a test comes back positive, you can be confident that there was SARS-CoV-2 viral RNA in the specimen collected from the patient. However, the sensitivity of these tests varies based on both the timing and the way the sample is collected.