Comparative performance study of six commercial molecular assays for rapid detection of toxigenic Clostridium difficile.

OBJECTIVES: Rapid and accurate detection of Clostridium difficile in stool affects patient treatment and containment efforts. Detection of C. difficile toxin genes using nucleic acid amplification techniques (NAAT) is part of a multistep algorithm. Our objective was to directly compare the diagnostic accuracy and applicability of six commercial C. difficile NAAT.

METHODS: Two hundred ten specimens were analysed in parallel by six commercial NAAT. Toxigenic culture was used as a reference method.

RESULTS: We analysed 98 positive and 112 negative samples. The Xpert C. difficile had 99% sensitivity (95% confidence interval (CI) 94.45-99.97), followed by Simplexa C. difficile Universal Direct 95% (95% CI 88.49-98.32), Illumigene C. difficile, and Quidel AmpliVue C. difficile, both 93% (95% CI 85.84-97.08), and BDmax Cdiff and GenomEra C. difficile, both 92% (95% CI 84.55-96.41). All assays had very high specificity (>99%). Invalid results requiring retesting were the highest in GenomEra (6.7%; 14/210) and BDmax (4.3%; 9/210), followed by AmpliVue (1.4%; 3/210) and Xpert (0.96%; 2/210). No retesting was required with Simplexa and Illumigene. The turnaround time was the shortest for the Illumigene and Xpert and the longest for BDmax, mostly due to the different reaction times of assays. Total hands-on time was comparable for all six assays.

CONCLUSIONS: All assays had high sensitivity and specificity. The differences in turnaround time, repeat testing rates and platform characteristics could help laboratories decide which assay would integrate better in their setting and to better select a molecular platform for C. difficile detection.