The United States is at a “transition point” when it comes to diagnosing Clostridium difficile (C. diff), experts say. Complicating efforts to document the increasing burden of severe C. diff is the current migration of laboratories to more sensitive diagnostic tests for detection of the infection as well as the multitude of diagnostic testing strategies. Two recent studies highlight both the transition of testing approaches, as well as some of the remaining limitations on testing. Experts say either multistep approaches using polymerase chain reaction (PCR) for the toxin gene(s) or single-step PCR on liquid stool samples have the highest sensitivity and specific- ity. Yet, testing is unable to differentiate asymptomatic colonization and symptomatic infection, leading experts to remind clinicians that diagnostic testing for C. diff infection should be performed only in symptomatic patients. According to new data released by the U.S. Centers for Disease Control and Prevention (CDC) in a study published Feb. 26 in the New England Journal of Medicine (NEJM), C. diff caused almost half a million infections in the United States in 2011. A convenience sample of 37 clinical laboratories across the Emerging Infections Program (EIP) sites submitted all C. diff–positive stool specimens from cases with full […]
The United States is at a “transition point” when it comes to diagnosing Clostridium difficile (C. diff), experts say. Complicating efforts to document the increasing burden of severe C. diff is the current migration of laboratories to more sensitive diagnostic tests for detection of the infection as well as the multitude of diagnostic testing strategies. Two recent studies highlight both the transition of testing approaches, as well as some of the remaining limitations on testing.
Experts say either multistep approaches using polymerase chain reaction (PCR) for the toxin gene(s) or single-step PCR on liquid stool samples have the highest sensitivity and specific- ity. Yet, testing is unable to differentiate asymptomatic colonization and symptomatic infection, leading experts to remind clinicians that diagnostic testing for C. diff infection should be performed only in symptomatic patients.
According to new data released by the U.S. Centers for Disease Control and Prevention (CDC) in a study published Feb. 26 in the New England Journal of Medicine (NEJM), C. diff caused almost half a million infections in the United States in 2011. A convenience sample of 37 clinical laboratories across the Emerging Infections Program (EIP) sites submitted all C. diff–positive stool specimens from cases with full medical-record review for culture, with recovered isolates undergoing pulsed-field gel electrophoresis. Isolates also underwent PCR assay. Additionally, all laboratories were surveyed to assess the type of C. diff diagnostic tests that they use. The CDC’s incidence and burden estimates are based on use of nucleic acid amplification testing by 52 percent of labs, which was observed across EIP sites.
Researchers, who conducted a separate systematic review of the diagnosis and treatment of C. diff, found that diagnostic approaches are complex due to the availability of multiple testing strategies. The review, published in the Jan. 27 issue of the Journal of the American Medical Association, found that even with highly sensitive tests, testing can be time intensive and still provide data of limited utility, including the failure to distinguish between asymptomatic C. diff colonization and symptomatic infection, making test of cure futile.
“I think that the best way to sum it up is that we need to use better methods overall in diagnosing C-difficile and that includes the basics of determining who should be tested,” said Clifford McDonald, M.D., from CDC’s Division of Healthcare Quality Promotion, on a telebriefing. “If you use a very sensitive test, but are very selective in how you decide it should be used or who to test, it’s a very good way to diagnose diseases, in general. If you use highly sensitive tests indiscriminately, you’ll end up over diagnosing the infections.”
