All of the above tests may be used as detection assays for C. difficile. However, only the tissue culture toxin detection assay is the gold standard laboratory test. This test involves a specific toxin neutralizing antibody that detects toxin (Toxin A and B) production in the stool using a tissue culture detection assay. Not all C. difficile strains produce toxins, and the tox genes are not carried on either plasmids or phages.