title: Multicenter clinical evaluation of the portrait toxigenic C. difficile assay for detection of toxigenic Clostridium difficile strains in clinical stool specimens.
abstract: We compared the Portrait Toxigenic C. difficile Assay, a new semiautomated sample-to-result molecular test, to a toxigenic bacterial culture/cell cytotoxin neutralization assay (TBC/CCNA) for the detection of toxigenic Clostridium difficile in 549 stool specimens. Stool specimens were also tested by one of three alternative FDA-cleared molecular tests for toxigenic C. difficile (Xpert C. difficile, Illumigene C. difficile, or GeneOhm Cdiff). The sensitivities and specificities of the molecular tests compared to TBC/CCNA were as follows: 98.2% and 92.8% for the Portrait assay, 100% and 91.7% for the Xpert assay, 93.3% and 95.1% for the Illumigene assay, and 97.4% and 98.5% for the GeneOhm assay, respectively. The majority of Portrait false-positive results (20/31; 64.5%) were also positive for C. difficile by an alternative molecular test, suggesting an increased sensitivity compared to the culture-based "gold standard" method. The Portrait test detected an assay input of 30 CFU in 100% of spiked samples and detected an input of 10 CFU in 96.7% of samples tested.
authors.affiliation: Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Blake W
authors.initials: BW
authors.lastname: Buchan
authors.forename: Tami-Lea A
authors.initials: TL
authors.lastname: Mackey
authors.forename: Judy A
authors.initials: JA
authors.lastname: Daly
authors.forename: Garrison
authors.initials: G
authors.lastname: Alger
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Denys
authors.forename: Lance R
authors.initials: LR
authors.lastname: Peterson
authors.forename: Sue C
authors.initials: SC
authors.lastname: Kehl
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Ledeboer
mesh_terms: D000293:Adolescent; D001331:Automation / Q000379:methods; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques / Q000379:methods*; D016360:Clostridioides difficile / Q000302:isolation & purification*; D003015:Clostridium Infections / Q000175:diagnosis*; D005243:Feces / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D025202:Molecular Diagnostic Techniques / Q000379:methods; D012680:Sensitivity and Specificity