Clinical Yield of Routine Use of Molecular Testing for Adult Outpatients with Diarrhea

Background Molecular diagnostics for enteropathogens increase yield while reducing turnaround time. However, many pathogens do not require specific therapy, and the cost is substantial. Methods We reviewed the use of the FilmArray GI Panel (BioFire Diagnostics, Salt Lake City, Utah) in adult outpatients at the University of Virginia and identified clinical features that could limit testing without reducing yield. We defined yield as (a) detection of a pathogen, (b) detection of a pathogen for which antimicrobial therapy is indicated, or (c) detection of a pathogen that can change management, which additionally included viral pathogens in immunocompromised patients. Results Between March 23, 2015 and February 25, 2016, we reviewed 452 tests from adult outpatients with diarrhea. A pathogen was detected in 88/452 (19.5%). The most common pathogens were: enteropathogenic E. coli (36; 8.0%), norovirus (17; 3.8%), Campylobacter (7, 1.5%), enteroaggregative E. coli (6, 1.3%), Giardia (6; 1.3%), and sapovirus (5; 1.1%). Based on clinical guidelines, antimicrobial treatment was clearly indicated for 19/452 subjects (4.2%). Limiting testing to patients with an additional enteric symptom (abdominal pain, nausea, vomiting, fecal urgency, tenesmus, or flatulence), a travel history, or an immunocompromising condition would reduce testing by 25.9%, with a treatable pathogen identified in 18/331 (5.4%) (sensitivity 94.7%, specificity 27.7%). Further modifying testing criteria to exclude subjects with vomiting, 18/288 (6.3%) had a treatable pathogen (sensitivity 94.7%, specificity 37.3%), and a pathogen which could change management was detected in 28/288 (9.7%) (sensitivity 96.6%, specificity 38.5%). Excluding immunocompromised subjects or those with a travel history, American College of Gastroenterology guidelines for testing were met by 293/348 (84.2%) with a documented duration of diarrhea, and a treatable pathogen was detected in 8/293 (2.7%) vs. 3/55 (5.5%) who did not meet testing guidelines. Conclusion Testing could be reduced by 36.3% without decreasing clinical yield by limiting testing to patients with diarrhea with an additional enteric symptom and no history of vomiting, a travel history, or an immunocompromising condition. ACG guidelines did not improve testing efficiency. Disclosures All authors: No reported disclosures.