Molecular diagnostic tests detect nucleic acids, DNA or RNA, in a sample. It is usually impossible to detect a whole strand of DNA or RNA. Most often a specific region of DNA or RNA (called a target) that is unique to the organism, mutation, or disease is detected. Because these assays are detecting or quantifying biomolecules that are minute in size and concentration, special techniques are employed. Most assays include a component that is labeled and detection or measurement of the label is used to determine the presence or quantity of target in each sample.
Two common techniques used in molecular testing are hybridization and amplification.