Glutamate dehydrogenase (GDH) is the protein produced by all C. difficile bacteria, regardless of their toxin-producing ability. Testing for GDH is a good screening marker for C. difficile infection, but follow-up testing is necessary because we cannot tell from a GDH result alone if the strain can produce toxin, which makes patients sick. With a GDH-positive result alone, it is possible that the patient is simply a carrier.
C. difficile diagnosis can be challenging. It is possible to be a carrier of C. difficile, meaning that the bacteria is present, but is not producing disease-causing toxins that make people sick.
It is important to properly differentiate people with a true C. difficile infection from C. difficile carriers. Treating C. difficile carriers may make people more susceptible to a true C. difficile infection. Antibiotic treatments for the initial infection may also be unnecessarily stopped.