Exclusive reliance on molecular tests for Clostridium difficile (C. diff) infection diagnosis is likely to result in overdiagnosis, overtreatment, and increased health care costs, according to a study published in the November issue of JAMA Internal Medicine. Virtually all C. diff infection-related complications and deaths occur in patients with positive toxin immunoassay test results, not just positive molecular test results, indicating that treatment is likely unnecessary based solely on molecular testing. "Molecular tests should not be used as a stand-alone diagnostic test for CDI and diagnostic recommendations should move back in the direction of defining clinical disease as a positive toxin result in patients with diarrhea," write the authors led by Christopher Polage, M.D., from University of California, Davis. "Two-step testing with a screening test, such as polymerase chain reaction or glutamate dehydrogenase antigen detection, followed by a toxin test to confirm active infection is a reasonable diagnostic strategy." Molecular tests are increasingly used to diagnose C diff infection, but many molecular test-positive patients lack toxins that historically defined diagnosis, leading to some confusion as to which patients need treatment for pathogenic C. diff infections and which ones may just have bacterial colonization. The number of institutions using molecular tests […]