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New test detects C difficile more rapidly
Currently, stool samples are initially screened using a glutamate dehydrogenase enzyme-linked immunosorbent assay (ELISA) test, and then they are confirmed by polymerase chain reaction testing, according to Abigail Salmon, MSc, of the microbiology department at St. Vincent’s University Hospital in Dublin, Ireland. The new molecular test, which uses the 3M Integrated Cycler, significantly reduced the time required to do testing.
“Diagnosis of C. difficile can be accomplished by a number of different methods, with recent publications indicating that molecular methods may have improved detection sensitivity compared to ELISA based methods,” Salmon told Infectious Disease News. “Routine testing is now being instituted in many hospitals, which has brought about a need for a higher throughput molecular testing system.”
Salmon and colleagues tested 275 nonformed stool samples that were received as part of routine C. difficile testing. Samples were tested using the current two-test testing algorithm and the investigational one-test molecular testing algorithm. They calculated the sensitivity and specificity of the one-test algorithm.
Using the currently used two-test algorithm, 21 samples tested positive for C. difficile and 254 samples were negative. The molecular testing method detected 25 positive samples and 250 negatives. The positive predictive value was 88% and the negative predictive value was 100%.
“The single-test algorithm provides comparable results to the multi-test algorithm, and results were available much more rapidly than when using the two-tiered approach,” Salmon said. “Although the use of a nonmolecular test to do initial patient screening may provide initial cost benefits, the labor requirement is higher, and the delay in providing results may add additional cost to patient care and infection control efforts.” Disclosure: Ms. Salmon reports no relevant financial disclosures.