Consideration of a Broader Definition for "Companion Diagnostics"

I have posted a number of previous notes defining and discussing companion diagnostics. Here are three examples of such notes: A Closer Look at Companion Diagnostics; More Details About Roche's Companion Diagnostics Strategy; Revisiting Roche's Diagnostics Strategy. To quote from the first of them, the term can be defined in the following way:

Briefly stated, [companion diagnostics] is a strategy pursued by some IVD companies, Roche Diagnostics in particular, whereby the company develops a gatekeeper biomarker assay. This is a lab test that serves to qualify a patient for treatment with a particular drug. The most common example of such a test is the HER-2/neu assay that is required prior to treatment with Herceptin.

It occurred to me that we have probably been defining companion diagnostics too narrowly by limiting its use primarily to the measurement of serum biomarkers. I personally have begun to routinely assume that diagnostics, unless otherwise qualified, should be more broadly defined to include both the analysis of serum and tissue biomarkers as well as medical imaging procedures. I have posted a number of notes about molecular imaging, which is defined in the following way in the Wikipedia:

[Molecular imaging] differs from traditional imaging in that probes known as biomarkers are used to help image various targets or pathways, particularly. Biomarkers interact chemically with their surroundings and in turn alter the image according to the molecular changes occurring within the area of interest. This is markedly different from previous methods of imaging which primarily imaged differences in qualities such as densities or water content.

Accordingly and quite simply, I think that we now need to broaden our definition of companion diagnostics to include both the measurement of serum/tissue biomarkers as well as medical imaging and particularly molecular imaging. Such an approach also echoes my belief, expressed in a number of previous notes, that pathology, lab medicine, and radiology are becoming much more closely aligned and should now merge into a new discipline of diagnostic medicine. This broader definition for companion diagnostics also suggests that Roche, GE, and Siemens are embarking on very similar strategy in the pursuit of personalized medicine.