Evaluation of antigen-positive toxin-negative enzyme immunoassay results for the diagnosis of toxigenic Clostridium difficile infection

Clostridium difficile (C. difficile)-associated diarrhea (CDAD) is a challenging nosocomial infectious disease. C. DIFF Quik Chek Complete assay is widely used to detect glutamate dehydrogenase (GDH) antigen and toxin A/B of C. difficile simultaneously. However, the interpretation of GDH positive/toxin negative results is problematic.We performed a retrospective study of patients with GDH positive/toxin negative results to determine the probability of detecting toxigenic C. difficile and its risk factors. Between April 2012 and March 2017, we investigated cultures of fecal specimens followed by toxin detection tests. The clinical histories of patients with and without toxigenic C. difficile were compared using univariate- and multivariate-analyses. In total, 2675 patients were examined using C. Diff Quik Chek Complete assay. Among 356 GDH positive/toxin negative patients, cultures were performed in 220 cases and toxigenic C. difficile was recovered from 139 (63.2%) specimens. Patients with toxigenic C. difficile had significantly lower body mass index than those without. Over half the GDH positive/toxin negative patients were infected with toxigenic C. difficile. Lower BMI was a CDAD risk factor in this patient population. These data can be utilized to initiate isolation and clinical interventions before confirmatory test results are available.