Molecular diagnostics is a collection of techniques used to analyse biological markers in the genome and proteome—the individual's genetic code and how their cells express their genes as proteins—by applying molecular biology to medical testing. The technique is used to diagnose and monitor disease, detect risk, and decide which therapies will work best for individual patients . By analysing the specifics of the patient and their disease, molecular diagnostics offers the prospect of personalised medicine. These tests are useful in a range of medical specialisms, including infectious disease, oncology, human leucocyte antigen typing (which investigates and predicts immune function), coagulation, and pharmacogenomics—the genetic prediction of which drugs will work best.[4](v-vii) They overlap with clinical chemistry (medical tests on bodily fluids). During the 1990s, the identification of newly discovered genes and new techniques for DNA sequencing led to the appearance of a distinct field of molecular and genomic laboratory medicine; in 1995, the Association for Molecular Pathology (AMP) was formed to give it structure. In 1999, the AMP co-founded The Journal of Medical Diagnostics.[9] Informa Healthcare launched Expert Reviews in Medical Diagnostics in 2001.[1] From 2002 onwards, the HapMap Project aggregated information on the one-letter genetic differences that recur in the human population—the single nucleotide polymorphisms—and their relationship with disease.[2](ch 37) In 2012, molecular diagnostic techniques for Thalassemia use genetic hybridization tests to identify the specific single nucleotide polymorphism causing an individual's disease.

As the commercial application of molecular diagnostics has become more important, so has the debate about patenting of the genetic discoveries at its heart. In 1998, the European Union's Directive 98/44/ECclarified that patents on DNA sequences were allowable.[11] In 2010 in the US, AMP sued Myriad Genetics to challenge the latter's patents regarding two genes, BRCA1, BRCA2, which are associated with breast cancer. In 2013, the U.S. Supreme Court partially agreed, ruling that a naturally occurring gene sequence could not be patented.