The burden of clostridium difficile infection: estimates of the incidence of CDI from U.S. Administrative databases.
BACKGROUND
Many administrative data sources are available to study the epidemiology of infectious diseases, including Clostridium difficile infection (CDI), but few publications have compared CDI event rates across databases using similar methodology. We used comparable methods with multiple administrative databases to compare the incidence of CDI in older and younger persons in the United States.


METHODS
We performed a retrospective study using three longitudinal data sources (Medicare, OptumInsight LabRx, and Healthcare Cost and Utilization Project State Inpatient Database (SID)), and two hospital encounter-level data sources (Nationwide Inpatient Sample (NIS) and Premier Perspective database) to identify CDI in adults aged 18 and older with calculation of CDI incidence rates/100,000 person-years of observation (pyo) and CDI categorization (onset and association).


RESULTS
The incidence of CDI ranged from 66/100,000 in persons under 65 years (LabRx), 383/100,000 in elderly persons (SID), and 677/100,000 in elderly persons (Medicare). Ninety percent of CDI episodes in the LabRx population were characterized as community-onset compared to 41 % in the Medicare population. The majority of CDI episodes in the Medicare and LabRx databases were identified based on only a CDI diagnosis, whereas almost ¾ of encounters coded for CDI in the Premier hospital data were confirmed with a positive test result plus treatment with metronidazole or oral vancomycin. Using only the Medicare inpatient data to calculate encounter-level CDI events resulted in 553 CDI events/100,000 persons, virtually the same as the encounter proportion calculated using the NIS (544/100,000 persons).


CONCLUSIONS
We found that the incidence of CDI was 35 % higher in the Medicare data and fewer episodes were attributed to hospital acquisition when all medical claims were used to identify CDI, compared to only inpatient data lacking information on diagnosis and treatment in the outpatient setting. The incidence of CDI was 10-fold lower and the proportion of community-onset CDI was much higher in the privately insured younger LabRx population compared to the elderly Medicare population. The methods we developed to identify incident CDI can be used by other investigators to study the incidence of other infectious diseases and adverse events using large generalizable administrative datasets.
Division of Infectious Diseases, Washington University School of Medicine, Campus Box 8051, 660 S. Euclid Ave, St. Louis, 63110, MO, USA. molsen@wustl.edu.|Department of Surgery, Washington University School of Medicine, St. Louis, MO, USA. molsen@wustl.edu.
Margaret A
MA
Olsen
Department of Psychiatry, Geisel School of Medicine at Dartmouth, Hanover, NH, USA.
Yinong
Y
Young-Xu
Division of Infectious Diseases, Washington University School of Medicine, Campus Box 8051, 660 S. Euclid Ave, St. Louis, 63110, MO, USA.
Dustin
D
Stwalley
Department of Medicine, Harvard Medical School, Boston, MA, USA.
Ciarán P
CP
Kelly
Edward Hines Jr. Veterans Affairs Hospital, Hines, IL, USA and Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA.
Dale N
DN
Gerding
Division of Infectious Diseases, Washington University School of Medicine, Campus Box 8051, 660 S. Euclid Ave, St. Louis, 63110, MO, USA.
Mohammed J
MJ
Saeed
Sanofi-Pasteur, Lyon, France.
Cedric
C
Mahé
Division of Infectious Diseases, Washington University School of Medicine, Campus Box 8051, 660 S. Euclid Ave, St. Louis, 63110, MO, USA.
Erik R
ER
Dubberke
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003015:Clostridium Infections / Q000188:drug therapy / Q000191:economics* / Q000453:epidemiology; D016208:Databases, Factual; D005260:Female; D017048:Health Care Costs; D006761:Hospitals; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D006278:Medicare / Q000191:economics; D008795:Metronidazole / Q000627:therapeutic use; D008875:Middle Aged; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology; D014640:Vancomycin / Q000627:therapeutic use
D008795:Metronidazole; D014640:Vancomycin
Administrative data; Claims data; Clostridium difficile; Hospital-acquired infection; Incidence; Medicare data