Utility of repeating stool for clostridium difficile toxin within 48 hours

Background: Clostridium difficile infection (CDI) is a major cause of nosocomial infection; antibiotic associated diarrhea, psuedomembrane colitis and toxic mega colon. It is a condition that has quite significant morbidity and mortality. Many physicians still repeat stool for clostridium difficille toxin during a patient's hospital course. Clostridium difficile produces 3 toxins: toxin A which is an enterotoxin, toxin B (cytotoxin) and a substance that inhibits bowel motility. Many tests are used to make the diagnosis of CDI. The most commonly used one is the enzyme immune assay (EIA) for toxin A and toxin B. This test is the least expensive and the quickest to obtain results. The gold standard is the direct fecal cytoxicity test with sensitivity of up to 100%. However it is costly and time consuming. Objective: We will evaluate whether there is any significance in repeating a stool for clostridium difficile toxin within 48 hours. Methods: Repeated stool samples for clostridium difficile toxin were obtained from Saint Michaels Medical Center between Dec 1 2008 and July 31 2009. Stools were tested using the Premier Enzyme Immunoassay for the detection of clostridium difficile toxin A and toxin B which has a sensitivity of 94.7% and a specificity of 97.3%. Only the samples that were retested within 48 hours were included in the study. Results: Out of the 190 repeat stool samples, 75 (39.5%) were repeated within 48 hours. From the data collected, 5 patients (6.7%) had a negative result on the initial test and a positive result on the second test. 3 patients (4%) had a positive initial result and then negative result on repeat testing in 48 hours. However, these patients were receiving flagyl or vancomycin orally. Table 1 Results of 1st test Results of 2nd test Total Negative Negative 63 Positive Negative 3 Negative Positive 5 Positive Positive 4 Conclusions: Clostridium difficile infection is a major nosocomial infection if proper preventive and therapeutic measures are not taken early. Repeating stool for clostridium difficile testing is inexpensive and readily available. As our data showed, we can still detect about 6.7% of patient who missed the diagnosis of CDI initially, which may have lead to further deterioration of clinical symptoms including mega colon and death without early treatment. Our data showed there is some value of repeating testing in a patient with clinical suspicion for CDI and initial test is negative.