671. Introduction of simultaneous Clostridioides difficile Antigen and Toxin A and B detection for diagnosis of C. difficile related diarrhea at Michael E. DeBakey VA Medical Center

BACKGROUND: Nucleic acid amplification test (NAAT) for diagnosis of Clostridioides difficile infection (CDI) is highly sensitive but is unable to distinguish colonization from infection. Antigen/toxin testing on the other hand may have lower sensitivity, especially early in infection with associated delay in diagnosis. METHODS: We conducted a retrospective study at Michael E. DeBakey VA Medical Center prior and post the introduction of simultaneous C.difficile GDH Antigen and Toxin A/B (GDH/Tox) detection. RESULTS: In the pre-intervention period 83 patients underwent NAAT, 16 patients had a positive test result (19.3%). In the post-intervention 120 patients were tested; 99 (82.5%) were negative for both GDH Antigen and toxin A/B (GDH-/tox-), 16 (13.3%) tested positive for the GDH Antigen but negative for Toxin A/B (GDH+/tox-) and 5 (4.2%) tested positive for both Antigen and Toxin (GDH+/tox+). Two patients (1.7%) who initially tested GDH+/tox- were subsequently retested due to persistent symptoms or evidence of colitis and were noted to have GDH+/tox+ result. The rate of positivity of C.difficile testing in our institution decreased form 19.3% to 4.2% (p< .001) post introduction of the GDH/toxin A/B detection. The treatment rate of patients who had the test performed decreased from 18.1% to 9.2% (p=.062). 30-day readmission rate for any reason in the group that tested positive for CDI in the pre-intervention group was 18.5% (3 patients), with 30-day all-cause mortality 6.25% (1 patient). In the GDH+/tox+ and GDH+/tox- groups in the post-intervention period, the 30-day readmission rate for any cause was 9.5% (2 patients), and 30-day all-cause mortality was 6.25% (1 patient). CDI testing results before and after the intervention. [Figure: see text] CONCLUSION: Distinguishing asymptomatic carriage or colonization from CDI remains an important goal. Implementing GDH Antigen and toxin A/B C.difficile testing can help reduce the risk of inappropriate treatment of colonization and possibly reduce the risk for development of antibacterial resistant C.difficile strains, however in our case it initially missed 2 cases of CDI that fortunately was not associated with negative outcome. With use of the GDH/tox test repeat testing and/or treatment might be considered on case-by-case basis depending on persistence of symptoms or high suspicion of infection. DISCLOSURES: All Authors: No reported disclosures