Vancomycin Therapy for Severe Clostridium difficile--Associated Diarrhea

To The Editor—We applaud the efforts of Zar et al. [1] in conducting a randomized trial of therapy for Clostridium difficile–associated diarrhea (CDAD); effective therapy for CDAD has been a neglected area of research, despite its frequency in modern health care systems [2]. However, the findings of this study [1] should be treated with caution until several issues have been addressed. First, an element of bias may have been introduced by the trial definition of treatment failure as “persistence of diarrhea and/or a positive result of a C. difficile toxin A assay at days 6 and 10 of treatment” [1, p. 303]. Successful treatment of CDAD is usually judged by resolution of symptoms, regardless of the persistence of toxin positivity, because toxin can frequently be detected in fecal samples for a period of time after appropriate treatment. Therefore, a primary analysis on the basis of symptom resolution should be performed.