Positive predictive value of the immunoassay for Clostridium difficile toxin A and B detection at a private hospital

Abstract

Introduction: Clostridium difficile (C. difficile) is a Gram-positive bacillus that is a common cause of diarrhea in the hospital environment, with a documented incidence of up to 10%. There are different methods to detect it, but a widely used test in our environment is the immunoassay for toxins A and B. Aims: The aim of our study was to 1) estimate the positive predictive value of the immunoassay for the detection of the C. difficile toxins A and B, 2) to establish the incidence of C. difficile associated diarrhea in the hospital, and 3) to know the most common associated factors. Methods: A diagnostic test accuracy study was conducted within the time frame of January 2010 to August 2013 at the Hospital Christus Muguerza® Alta Especialidad on patients with symptoms suggestive of C. difficile-associated diarrhea that had a positive immunoassay test and confirmation of C. difficile through colon biopsy and stool culture. Results: The immunoassay for toxins A and B was performed in 360 patients. Fifty-five of the cases had positive results, 35 of which showed the presence of C. difficile. Incidence was 10.2% and the positive predictive value of the test for C. difficile toxins A and B was 0.64 (95% CI, 0.51-0.76). Previous antibiotic therapy (n = 29) and proton pump inhibitor use (n = 19) were the most common associated factors. Conclusions: C. difficile incidence in our environment is similar to that found in the literature reviewed, but the positive predictive value of the test for toxin A and B detection was low.

Keywords

• Antibiotic-associated diarrhea
• Clostridium difficile
• Toxin A and B detection immunoassay
• Positive predictive value
• Culture