Molecular diagnosis is a technology that applies molecular biology methods to detect changes in the structure or expression level of the subject or the genetic material carrying viruses or pathogens, and to make a diagnosis based on the test results. The detection objects are mainly nucleic acids (DNA and RNA) and proteins, mainly nucleic acid molecules.

Compared with the mature immunodiagnosis, biochemical diagnosis and other technologies, molecular diagnosis is in a rapid growth stage and is the fastest growing subdivision in the field of in vitro diagnosis. It has the advantages of short detection time, high sensitivity, and strong specificity, and is widely used. In infectious diseases, prenatal and postnatal care, blood screening, genetic diseases, tumor-associated diagnosis and other fields, infectious diseases account for the highest proportion and have the most significant clinical value.

From a technical point of view, the field of molecular diagnosis mainly includes PCR (traditional PCR, qPCR and dPCR), fluorescence in situ hybridization (FISH), gene chip and second-generation high-throughput sequencing technology (NGS).