User: What is a PCR test?
Assistant: PCR stands for "polymerase chain reaction". This test uses cycles of heating and cooling to detect photons that are emitted when a reagent (binder) RNA binds to the viral RNA that has been extracted from the human sample. Each heating and cooling cycle increases (amplifies) the amount of the targeted genetic material in the test tube. If the intensity of the photons does not reach a threshold after a certain number of cycles, the PCR test will result in a "Not Detected" test result.