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With the continued rise in COVID-19 cases around the world, it has become imperative to identify individuals with the condition accurately. The diagnostic testing field for COVID-19 is evolving rapidly and improving in quality every day, with many tests focused on diagnosing patients with active viral infections. Diagnostics that detect current, active infections are typically molecular-based and inform investigators of the presence of the virus, either by identifying its genetic material or identifying unique markers of the pathogen. There are also rapid antigen tests in development that detect specific surface markers on the outside of the virus.

A few of these tests have received FDA emergency use authorisation (EUA) and are available on the market now. A viral nucleic acid test confirms a current infection. While an antibody test informs of an infection it might not indicate a current infection because it can take 1–3 weeks after infection to make antibodies. Having antibodies to the virus that causes COVID-19 might provide protection from getting infected with the virus again. If it does, we do not know how much protection the antibodies might provide or how long this protection might last. Hindering the utility and appropriate application of test methods are the sheer numbers of patients admitted to hospital and the wide array of symptoms that may be present in individuals with COVID-19.

An in-depth understanding of the symptoms that are unique to COVID-19 is essential if clinicians are to recommend nucleic acid or antibody testing. In addition, prior to the laboratory testing of samples, precise methods of sample collection, transport, and storage must be specified and properly carried out. This chapter briefly highlights the various symptoms that patients with COVID-19 may display, appropriate and accurate sample collecting methods, the progression of the disease over the course of two weeks or more post-infection, and guidelines for evaluation of the disease. This chapter also inventories the various diagnostic methods that have been deployed and elaborates on the advantages and disadvantages of each.