Bosch DE, Mathias PC, Krumm N, et al. - This study was carried out to assess whether increased white blood cell count (WBC) predicts Clostridium difficile nucleic acid testing (NAAT) results. Researchers conducted a retrospective review of laboratory testing, outcomes, and treatment of 16,568 consecutive patients presenting to four hospitals over 4 years with NAAT and WBC testing on the same day. An isolated WBC elevation has low sensitivity and specificity as a predictor of fecal Clostridium difficile NAAT positivity in the inpatient setting, even as WBC is an important prognostic indicator in patients with Clostridium difficile infection (CDI). For CDI testing, a high or rising WBC in isolation is not a sufficient indication.