A Diagnostic Algorithm for the Detection of Clostridium difficile-Associated Diarrhea

Abstract

Background:Clostridium difficile is a common cause of hospital-acquired diarrhea, which is usually associ-ated with previous antibiotic use. The clinical manifesta-tions of C. difficile infection (CDI) may range from mild diarrhea to fulminant colitis. Clostridium difficile should be considered in diarrhea cases with a history of antibi-otic use within the last 8 weeks (community-associated CDI) or with a hospital stay of at least 3 days, regardless of the duration of antibiotic use (hospital-acquired CDI). Aims: This study investigated the frequency of CDI in diarrheic patients and evaluated the efficacy of the triple diagnostic algorithm that is proposed here for C. difficile detection. Study Design: Cross-sectional study. Methods: In this study, we compared three methods currently employed for C. difficile detection using 95 patient stool samples: an enzyme immunoassay (EIA) for toxin A/B (C. diff Toxin A+B; Diagnostic Auto-mation Inc.; Calabasas, CA, USA), an EIA for gluta-mate dehydrogenase (GDH) (C. DIFF CHEK-60TM, TechLab Inc.; Blacksburg, VA, USA), and a poly-merase chain reaction (PCR)-based assay (GeneXpert®C. difficile; Cepheid, Sunnyvale, CA, USA) that detects C. difficile toxin genes and conventional methods as well. In this study, 50.5% of the patients were male, 50 patients were outpatients, 32 were from inpatient clin-ics and 13 patients were from the intensive care unit. Results: Of the 95 stool samples tested for GDH, 28 were positive. Six samples were positive by PCR, while nine samples were positive for toxin A/B. The hyper-virulent strain NAP-1 and binary toxin was not detect-ed. The rate of occurrence of toxigenic C. difficile was 5.1% in the samples. Cefaclor, ampicillin-sulbactam, ertapenem, and piperacillin-tazobactam were the most commonly used antibiotics by patients preceding the onset of diarrhea. Among the patients who were hospi-talized in an intensive care unit for more than 7 days, 83.3% were positive for CDI by PCR screening. If the PCR test is accepted as the reference: C. difficile Toxin A/B ELISA sensitivity and specificity were 67% and 94%, respectively, and GDH sensitivity and specificity were 100% and 75%, respectively.Conclusion: Tests targeting C. difficile toxins are fre-quently applied for the purpose of diagnosing CDI in a clinical setting. However, changes in the temperature and reductant composition of the feces may affect toxin stability, potentially yielding false-negative test results. Therefore, employment of a GDH EIA, which has high sensitivity, as a screening test for the detection of toxi-genic strains, may prevent false-negative results, and its adoption as part of a multistep diagnostic algorithm may increase accuracy in the diagnosis of CDIs