Several laboratory methods are currently available to aid in the detection of C. difficile, including culture for toxigenic C. difficile (considered the "gold standard" for viable C. difficile detection), detection of Toxin A, B, or both, and molecular detection methods. These methods differ in their sensitivity and specificity and should always be used in conjunction with clinical considerations. To make the diagnosis, it is usually only necessary to submit 1–2 diarrheic (non-formed) stools per episode.
Once positive for C. difficile by any laboratory method, there is no need for follow-up assays to make sure the organism or toxins are absent from the initial episode. If assays are performed for subsequent episodes, culture or tissue culture assay for Toxin B is probably most appropriate to avoid the possibility of detecting the initial antigen, toxin, or gene.
