Controversies in Clostridium difficile testing

Recent reports of two nosocomial outbreaks of Clostridium difficile-associated disease caused by toxin A-deficient strains emphasize that these strains can cause disease. Laboratories using an assay that detects only toxin A as their primary diagnostic test risk misdiagnosis of cases or outbreaks in the institutions they serve. Repeat testing can account for a significant portion of a laboratory's C. difficile testing workload. Published data are available to support laboratory rules for rejection of repeat stool specimens within 7 days of an initial specimen. There are also substantial published data to support laboratory rejection of formed stools sent to the laboratory for C. difficile testing.