Electronic Surveillance of Antibiotic Exposure and Coded Discharge Diagnoses as Indicators of Postoperative Infection and Other Quality Assurance Measures

OBJECTIVES: To assess postoperative exposure to parenteral antibiotics and coded discharge diagnoses of infection as markers of nosocomial infection, postoperative morbidity, and potentially inappropriate antibiotic use after cesarean section. DESIGN: Retrospective cohort study to compare automated markers with the criterion of record review. SETTING: Tertiary care hospital. PATIENTS: Women admitted to a large teaching hospital after April 15, 1987, and discharged before October 1, 1989, who underwent a nonrepeat, nonelective cesarean section and had received prophylaxis with a cephalosporin. METHODS: Antibiotic exposure and discharge diagnosis codes were obtained from a large electronic hospital data base. A sample of charts was reviewed to determine the presence of infection, other postoperative complications, and postoperative antibiotic exposure. RESULTS: A total of 2,197 women who had undergone a nonrepeat nonelective cesarean section were included in the study cohort. These women were assigned to 6 subgroups based on postoperative antibiotic exposure status and discharge codes suggesting endometritis, other postoperative infection, or no infection. Review of 457 records indicated that the overall infection rate was 9%. Eight percent of all the patients had a coded diagnosis for infection, and 16% received some parenteral antibiotics after the first postoperative day. Exposure to at least 2 days of parenteral postoperative antibiotics was the best marker by which to discriminate between infected and uninfected patients, with a sensitivity of 81%, a specificity of 95%, and a positive predictive value of 61% for detecting infection. The corresponding figures for coded diagnoses for infection had rates of 65%, 97%, and 74%, respectively. The combination of discharge codes and exposure to parenteral postoperative antibiotics resulted in a more accurate but less sensitive marker for nosocomial infections, with a positive predictive value of 94% and a sensitivity of 59%. The groups with discordant parenteral postoperative antibiotics exposure and discharge codes for infection were enriched for errors in coding, noninfectious morbidity, and unexplained antibiotic use. Less than 1% of the entire cohort had > or = to 2 days of parenteral postoperative antibiotics without any reason apparent in the medical record. CONCLUSIONS: Parenteral postoperative antibiotic exposure determined from automated pharmacy records correlated with the results of the more labor-intensive manual review of medical records for the identification of nosocomial infection. In addition, information on antibiotic exposure combined with coded discharge diagnoses provided a rapid screen to identify subgroups of patients with higher rates of infectious and noninfectious morbidity, unexplained antibiotic use, and errors in discharge coding. Information derived from electronic data bases created for administrative purposes may be useful as a marker for infectious complications, inappropriate antibiotic prescribing, and other issues related to total quality hospital monitoring.