Three-centre evaluation of laboratory Clostridium difficile detection algorithms and the EntericBio® realtime C. difficile assay.

ABSTRACT

The comparatively high cost of laboratory detection methods for Clostridium difficile infection (CDI) coupled to a low prevalence rate has resulted in testing algorithms that use cheaper and relatively sensitive screening methods, followed by more specific confirmatory methods. The aim of this prospectively-conducted study from two centres in the UK, and one in the Republic of Ireland was to determine the efficacy of the EntericBio® realtime C. difficile Assay (EBCD) for the detection of toxigenic C. difficile in stool samples. The EBCD was compared to the in-use testing methods for Clostridium difficile (CD) detection in each centre. In the two UK centres, the EBCD was compared to the C.diff Quik Chek Complete® kit (Techlab), and discrepancies were tested further using The Xpert®C. difficile PCR assay (Cepheid) and PCR ribotyping after cultivation using the spore culture method, respectively. In the Irish centre, EBCD comparison was to an algorithm of C. DIFF CHEK™-60 test (Techlab) for screening followed by C. difficile Premier ™ Toxins A&B assay (Meridian Bioscience®) in the case of positive results; discrepancies were tested using the Xpert®C. difficile PCR assay. In a retrospective analysis of data, a total of 947 stool samples were tested, of which eight (0.8%) proved inhibitory to the EBCD assay. Of the 939 valid tests conducted, reported sensitivities of the EBCD were 94.7%, 100% and 97.9%, respectively; specificities were 99.6%, 100% and 100%, respectively; positive predictive values were 94.7%, 100% and 100%, respectively, and negative predictive values were 99.6%, 100% and 99.8%, respectively. The CD positivity rates in the current study ranged between 6.6% and 8.2%.