New molecular diagnostics are an important addition to clinical and classical diagnostic procedures in neurology. Along with biomarkers, companion diagnostics are contributing to the safer and more effective use of therapeutics. The trend for the combination of diagnostics with therapeutics is useful for some disorders affecting the nervous system such as Alzheimer and Parkinson diseases. The advantages of this combination override some of the limitations and will be an important part of personalized neurology.
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• Molecular diagnostics can help in matching the appropriate drug for a disease in an individual patient.
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• Advances in brain imaging and the discovery of biomarkers of neurologic disorders are important contributions in this area.
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• There are several advantages, but limitations of combination of diagnosis with therapeutics should also be noted.
Historical note and terminology
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, various developments will change the pattern of current medical practice. Advances in medical genetics, genomics, molecular diagnostics, and biotechnologies will enable integrated healthcare systems incorporating genetic screening, prevention, diagnosis, therapy, and monitoring, which are also components of personalized medicine (12). 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. 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. Companion diagnostics is a recognized term for tests that are used to determine if the patient has a suitable indication for use of an accompanying drug. Most of these are used for detecting gene polymorphisms in anticancer therapy and several are approved by the FDA. 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. Integration of diagnostics and therapeutics is important for the development of personalized medicine (11). 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 rather than academic or government organizations. Although the industry has a vested interest in the development of combined systems, there are advantages for the physicians as well.