Multiplex Molecular Stool Testing Rarely Impacts Antimicrobial Treatment Decisions More Than Three Days After Admission

Background Acute diarrheal illness in the United States is a significant cause of healthcare utilization and hospitalizations. For patients who develop diarrhea while hospitalized, testing for pathogens other than Clostridium difficile (C. difficile) using conventional stool testing is low yield. Newer testing modalities for infectious diarrhea such as the multiplex molecular stool testing provide an improved detection rate and a faster turn-around time compared to conventional stool testing. Methods We retrospectively examined the use of a multiplex molecular stool test at our institution for all hospital encounters over a two-year period to determine which organisms were identified ≤ 3 days and > 3 days after admission. Results A total of 2032 patients underwent multiplex molecular stool testing during the study period, with 1698 (83.6%) performed ≤ 3 days and 334 (16.3%) > 3 days after admission. An enteric non-C. difficile pathogen was identified more frequently when patients were tested ≤ 3 days after admission (350, 20.6%) as compared to > 3 days after admission (38, 11.4%, p<0.0001). Excluding coinfections, C. difficile was identified more frequently when patients were tested > 3 days after admission (64, 20.3%) versus another organism (30, 9.0%) (p<0.0001). Of those patients with a non-C. difficile pathogen identified > 3 days after admission, a bacterial pathogen amenable to treatment was only identified in 6% (21) of patients. Conclusion Multiplex molecular stool testing for patients tested > 3 days after admission is a low yield of information that could guide antimicrobial treatment decisions, and C. difficile testing is more useful in this clinical situation.