Any of various techniques that are used to detect specific target sequences of nucleic acid (RNA or DNA) in a sample. Such techniques are widely used in research, clinical medicine, and industry, e.g. to detect or assay the presence of infective organisms or viruses in samples of blood, tissue, food, or other material. Many such techniques utilize variants of the polymerase chain reaction (PCR) to isolate and amplify the target sequence. Simpler and cheaper alternatives have been devised without the heating and cooling cycles of PCR, to make nucleic acid testing in the field or clinic more feasible.