The existence of prior art isn’t always readily evident when companies in the device and diagnostic spaces file patent applications with the U.S. Patent and Trademark Office (PTO). As it turns out, literature describing that prior art need not be widely distributed to invalidate a patent as Quest Diagnostics Inc., of Secaucus, N.J., recently discovered, an object lesson for all in the med-tech space that research for prior art must be exhaustive if a patent is to hold up over time.