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timing and position of the detection that indicates the position of the molecule in
time and space. Images can then be constructed tomographically, and regional time
activities can be derived. The kinetic data produced provide information about the
biological activity of the molecule. Molecular imaging provides in vivo information
in contrast to the in vitro diagnostics. Moreover, it provides a direct method for the
study of the effect of a drug in the human body. Molecular imaging plays a key role
in the discovery and treatment process for neurological diseases such as Alzheimer’s
and cancer. The ability to image biological and pathological processes at a molecu-
lar level using PET imaging offers an unparalleled opportunity to radically reform
the manner in which a disease is diagnosed and managed. Its translation into clinical
practice will impact upon personalized medicine.
Combination of Diagnostics and Therapeutics
The term “theranostic” is used to denote linking of a diagnostic to therapeutic. The
second half of the word “nostic” is supposed to represent diagnostic but sounds
more like “gnostic”, a word introduced into English from Latin and meaning “having
knowledge of”. Theranostic could thus mean having knowledge of therapy.
Moreover “theranostic” is confusing and not understood by most people. There is
no diffi culty in describing this concept without using a special term. Diagnostics
used to guide therapeutics are also called “companion diagnostics”. If one has to use
a single word to describe a test linked to therapy, one can use “pharmacodiagnostic”,
which is more appropriate and easier to understand. This textbook does not recom-
mend the use of the term ”theranostic”.
Use of Molecular Diagnostics for Stratifi cation in Clinical Trials
One of the problems in clinical trials is that response to a drug may vary consider-
ably among patients. Some patients are poor or moderate responders, or the drugs
themselves work well only in subsets of those treated. Effi cacy and safety decisions
are based on overall results of randomized clinical trials in which the therapeutic
outcomes and clinical utility of a drug are averaged for entire populations. It is not
possible to predict usefulness of such drugs in individual patients.
Stratifi cation is a method of classifying patients based on clinically relevant
genetic and/or immunological information during clinical trials of therapies and
later application in practice. Such stratifi cation is performed by the evaluation of
clinically meaningful information generated by an appropriate molecular diagnostic
test, which can guide in differentiating responders from non-responders to a therapy
and selecting patients for treatment. This may be useful for matching the right drug
to the right patient.
2 Molecular Diagnostics in Personalized Medicine