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). Among them, PCR is currently the most mature technology platform with the largest market share, with a market share of up to 40% in domestic molecular diagnostics; followed by molecular hybridization technology, accounting for 35%.

1. Polymerase Chain Reaction (PCR)

In the 1980s, Kary Mullis, a chemist at Cetus Corporation, invented PCR, which gave a huge boost to molecular biology and even the life science community. Since then, PCR-based DNA amplification technology has gradually become the basis of biological research, opening one after another major topics in the field of life sciences. At present, PCR is widely used in the diagnosis of infectious diseases (bacteria, fungi, viruses, mycoplasma), NIPT, stem cell research, and biomarker development.

PCR refers to DNA polymerase (also known as "DNA polymerase", such as Taq DNA polymerase) catalyzed by DNA polymerase as a template, specific primers as the starting point for extension, high temperature denaturation (94 ℃), low temperature renaturation (55°C), intermediate temperature extension (72°C) and other steps, the process of replicating the daughter strand DNA complementary to the parent strand template DNA in vitro. PCR is a special DNA replication in vitro. The biggest feature is that it can greatly amplify a small amount of DNA.

Compared with hybridization technology and high-throughput sequencing technology, the main advantages of PCR technology are high sensitivity and easy promotion. The main limitation is that the detection site is single and known, and the number of genes that can be covered in the combined detection of multiple genes is limited. But in the short term, PCR technology will still be the mainstream technology platform for molecular diagnostics.

Since its inception, PCR technology has experienced rapid development for more than 30 years, and has become the most mature molecular diagnostic technology platform in the world with the largest market share. Researchers have developed a series of derivative molecular detection technologies based on the principle of this technology, which can be divided into three categories: the first generation PCR electrophoresis, the second generation fluorescence quantitative PCR (qPCR) and the third generation digital PCR ( dPCR).