Historically, diagnosis has been a separate step prior to treatment and has been mainly based on clinical examination of the patient. Even with the development of brain imaging, advances in neurodiagnostics, and introduction of effective therapies, diagnosis has remained distinct from therapeutics. There are isolated procedures, such as obliteration of an arteriovenous malformation by embolization, in which diagnostic angiography is combined with a therapeutic procedure. With increase in subspecialization, some of the special diagnostic laboratory procedures are detached from the routine clinical practice of neurology.
With the impact of genomics on neurology, a number of developments will change the pattern of current medical practice. Advances in medical genetics, molecular diagnostics, and genome-based medicines will enable integrated healthcare systems incorporating genetic screening, prevention, diagnosis, therapy, and monitoring, which are also components of personalized medicine (Jain 2009). Diagnosis and therapy would be central in such a system, which will apply to neurology as well. A suitable term to describe the combination of diagnostics with therapeutics has not been coined as yet. The term "theranostics," which is being increasingly used in the literature, is a poor word construction to describe diagnostics used for selecting therapy, and its use is not recommended. A better term would be "pharmacodiagnostics," which indicates diagnosis linked to pharmacotherapy. The concept of personalized medicine includes selective genotype-based prescription of drugs to individuals for whom the drug should be safe and effective. For neurologic disorders, the term used is personalized neurology (Jain 2005). The first example of the combination of molecular diagnostics and therapeutics was in the management of AIDS. HIV genotyping tests were used to detect resistance to antiviral drugs and molecular diagnostics tests were conducted for viral quantification to monitor therapy. Currently, molecular diagnostics are used increasingly in cancer patients to select appropriate anticancer drugs.
The initiative for development of such systems has come from the pharmaceutical industry as no academic or government organization has yet taken interest in this approach. Although the industry has a vested interest in the development of combined systems, there are advantages for the physicians as well.
Research activity in biomarkers will facilitate the integration of diagnostics with therapeutics. Any specific molecular alteration of a cell either on DNA, RNA, or protein level can be referred to as a molecular biomarker. A biomarker is a characteristic that can be objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention. Biomarkers may be revealed by brain imaging. Biomarkers can serve as the basis for diagnostic tests as well as therapeutic agents (Jain 2010).