636. Misclassification of Community-Onset Clostridium difficile Infection (CDI) as Hospital-Onset CDI at an Academic Medical Center
Session: Oral Abstract Session: HAI Reporting: The Devil is in the Details
Thursday, October 8, 2015: 3:00 PM
Room: 5--AB
Background: The National Healthcare Safety Network (NHSN) utilizes a  ‘3-day rule’ from date of admission to clinical testing, to distinguish hospital-onset CDI (HO-CDI), a preventable hospital outcome, from CO-CDI - a measure of C. difficile influx used for risk-adjustment in the standardized infection ratio (SIR). However, since classification is dependent on when physicians test, we used data from an institutional quality improvement project to assess how often delayed testing of CO-CDI patients resulted in HO-CDI misclassification.

Methods: Adult patients had CDI risk factor data and a perianal swab collected on admission to 11 high CDI risk units at the UC Davis Medical Center. The swabs were tested by culture and polymerase chain reaction (PCR) to identify patients with toxigenic C. difficile.  Diagnostic testing for CDI was performed by toxin immunoassay on diarrheal stool by physician order. Admission risk factor, C. difficilesurveillance, and CDI diagnostic test data were analyzed for a 12-month period.

Results: Of 48 patients with admission data and incident HO-CDI, 21 (44%) had C. difficile detected on the admit swab (swab+). 17 of the 21 (81%) had CDI risk factors including nine patients (43% of swab+; 19% of HO-CDI) with active/recent diarrhea. None of the 21 swab+ patients were tested for CDI until after the third hospital day. The median time to CDI testing/HO-CDI diagnosis was 6 days [IQR 5, 7], 5.5 days [IQR 4, 8], and 11 days [6, 15] in swab+ patients with and without diarrhea, and swab- patients, respectively (P<.03).   Among 142 other patients with diarrhea and one or more other CDI risk factors on admission, only 57 (40%) were tested within the first 3 days. 

Conclusion: These results suggest that a significant proportion of patients with CDI symptoms, risk factors and probable CO-CDI are not tested within 3 days of admission leading to over-reporting of HO-CDI and under-reporting of CO-CDI. Improving timelier clinical testing of patients with CDI risk factors and diarrhea may improve clinical care and infection control as well as aid hospitals to improve their CDI SIR.  Further studies are warranted in other hospitals to confirm such delays in testing and determine how often asymptomatic colonization with in infecting strain precedes incident CDI by > 3 days.

Christopher Polage, MD1, Michael Kennedy, BS2, Clare Gyorke, BS3, Catherine Adamson, RN4, Stacy Hevener, RN4, Carol Robinson, RN, MPA4, Erik R. Dubberke, MD, MSPH, FIDSA, FSHEA5, L. Clifford Mcdonald, MD, FSHEA6 and Stuart H. Cohen, MD, FIDSA, FSHEA7, (1)Pathology and Infectious Diseases, University of California, Davis Medical Center, Sacramento, CA, (2)Pathology and Laboratory Medicine, University of California, Davis School of Medicine, Sacramento, CA, (3)University of California, Davis Medical Center, Sacramento, CA, (4)University of California Davis Medical Center, Sacramento, CA, (5)Infectious Diseases, Washington University School of Medicine, St. Louis, MO, (6)Centers for Disease Control and Prevention, Atlanta, GA, (7)Internal Medicine, University of California, Davis Medical Center, Sacramento, CA


C. Polage, Cepheid: Investigator , Research reagents & materials (test kits)
Alere: Investigator , Speaker honorarium
Nanosphere: Grant Investigator , Research grant and Salary
Meridian: Investigator , Research reagents & materials (test kits)
TechLab: Investigator , Research reagents & materials (test kits)

M. Kennedy, None

C. Gyorke, None

C. Adamson, None

S. Hevener, None

C. Robinson, None

E. R. Dubberke, rebiotix: Consultant and Investigator , Consulting fee and Research support
sanofi-pasteur: Grant Investigator , Research grant
pfizer: Consultant , Consulting fee
Merck: Consultant and Investigator , Consulting fee and Research support

L. C. Mcdonald, None

S. H. Cohen, None

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