@HealthMed Diagnostics can be used in several ways: to establish the nature, subtype and severity of disease; to monitor wanted response to treatment with lifestyle, drugs and/or devices; to monitor for disease progression and for adverse effects of treatment. The term 'companion diagnostics' describes coupling diagnostic imaging or laboratory investigations with selection and monitoring of treatment. Although a logical idea, its use in the medical setting appears surprisingly recent.
In the late and 1980s and 1990s, reports of the use of combination diagnostics appear largely applying to veterinary and dental practice.
The partner term 'companion therapeutics' was used in a 2003 commentary on the FDA "Draft Guidance for Industry: Pharmacogenomic Data Submission" issued on November 3, 2003, which noted that the [pharmaceutical and biotech] 'industry is now expected to accelerate its development of diagnostics and companion therapeutics towards the goal of personalized medicine'. Implicit in this evolution of a personalised approached to medicines is the recognition that diagnostics will not necessarily identify that a given patient may have a safe or effective treatment flagged as the result of testing.
An early example of a pharmacogenetic companion diagnostic is the UGT1A1 molecular assay for in vitro diagnostic use. This pharmacogenetic test was approved in 2005 by the FDA for use as a companion diagnostic to a specific drug therapy. The test was to be used to identify mutations in this gene in patients who may as a result be at increased risk of adverse reaction to the anti-cancer drug irinotecan.
2006 and 2007 discussion of companion diagnostics pointed both to more efficient patient selection for clinical trials and a more profitable approach for drug developers.
Current descriptions use narrower definitions of companion diagnostics as referring to tests to 'identify and detect genetic, protein, or gene expression markers to predict whether a drug works or causes adverse effect in patients'. However there is a long history of coupling tests with treatment choice and refinement, in every therapeutic area from cardiovascular disorders such as hypertension and raised cholesterol, to anaemia and treatment of lung, gastro-intestinal, renal and neurological disease.
To date there are only 75 publications in the PubMed research database with companion diagnostics as a key term, with a typical recent example from August 2011 in Nature Reviews on Clinical Oncology by La Thangue and Kerr applied to cancer chemotherapy: Predictive biomarkers: a paradigm shift towards personalized cancer medicine.