Original ArticleAdministrative data accurately identified intensive care unit admissions in Ontario
Introduction
Administrative databases are used in health services research because they offer large and comprehensive sample size, systematic and coordinated data collection, and population-based information free of referral bias. We evaluated the accuracy of the Canadian Institute of Health Information database (which contains demographic, administrative, and clinical data for all hospital discharges and day surgeries in Canada), and the Ontario Health Insurance Program database (which contains all fee-for-service claims paid for services provided to Ontario residents) for identifying intensive care unit admissions.
Admission to the Critical Care Research Network (CCR-Net) database was our criterion standard. The CCR-Net is a collaboration including 33 Ontario hospitals that maintains a patient registry of the activities of critical care facilities [1], [2], [3]. The minimal dataset of admissions is systematically collected by participating hospitals and includes patient demographics, data to calculate a score on the Acute Physiology and Chronic Health Evaluation II (APACHE II) system [4], and information about ICU and hospital length of stay. The CCR-Net data has good interobserver reliability and strong face validity [5], [6], [7].
Section snippets
Selection of hospitals and patients
We considered all admissions (according to date of arrival) to nine Ontario acute care hospitals (including one teaching hospital) participating in the CCR-Net and appearing in the Canadian Institute of Health Information (CIHI) database during January 1, 2001 to December 31, 2002. The specific hospitals were selected based on the rates of successful linkage (>90% agreement) between the CIHI and CCR-Net databases (Appendix 1).
Handling of duplicate records
The patient admission to CIHI containing the most recent discharge
Results
During the 2-year study interval a total of 329,284 admissions to CIHI with valid health care numbers occurred at the nine hospitals. After deleting 203 duplicate records, 329,081 admissions were available for analysis. During the same time period, 19,876 records appeared in CCR-Net and successful linkage to CIHI was possible for 18,637 (94%). After removing 936 records in CCR-Net representing readmissions to ICU during the same hospital admission, 17,701 ICU admissions served as the criterion
Discussion
We explored administrative data from multiple Ontario hospitals and found that the databases can identify ICU patients. Several strategies were evaluated, but no one strategy simultaneously provided ideal sensitivity, specificity, and positive predictive value. OHIP codes and CIHI SCU codes had excellent sensitivity and specificity, but their associated positive predictive values were only fair (54 and 35%, respectively). This is not surprising, given the low overall frequency (prevalence 5.4%)
Acknowledgments
All authors participated in the study design, interpretation of results, and writing of the final draft. The corresponding author had full access to all the data in the study, and had final responsibility for the decision to submit for publication. No author has a financial conflict of interest that could inappropriately bias this work. Donald A. Redelmeier is supported by the Canada Research Chair in Medical Decision Sciences.
We are indebted to Dr. Andreas Laupacis for providing helpful
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