The use of health administrative data in health services research is facilitated by standardized classification systems, such as the International Classification of Diseases (ICD). Canada, among other countries, recently introduced the tenth version of ICD and its accompanying Canadian Classification of Interventions (CCI). It is imperative to assess errors that could occur in administrative data due to the introduction of the new coding system.
To evaluate the validity of procedure coding in hospital discharge data, comparing CCI with ICD-9-CM.
Trained reviewers examined 4008 randomly selected charts from 4 teaching hospitals in Alberta, Canada, for the presence of 30 procedures. The charts, already coded using CCI, were recoded using ICD-9-CM. Comprehensive lists of procedure codes in both systems were identified using literature, health records technicians, surgeons and online resources.
Three databases were created for the same hospital discharge record, including CCI, ICD-9-CM, and chart review data. Sensitivity, specificity, positive predictive value, negative predictive value and kappa scores were calculated.
Compared with the chart review data, ICD-9-CM data under-reported 17 procedures, over-reported 12, and equivalently reported 1. CCI data under-reported 19 procedures, over-reported 9, and equivalently reported 2. Kappa value was within 0.1 difference between ICD-9-CM and CCI for 14 procedures.
Both ICD-9-CM and CCI coded the more major or invasive procedures reasonably well, but were not valid for less invasive or minor procedures. CCI can be used by health services and population health researchers with as much confidence as ICD-9-CM.
From the *Department of Community Health Sciences, University of Calgary; †Quality, Safety and Health Information, Calgary Health Region; ‡Centre for Health and Policy Studies, University of Calgary, Calgary, Alberta, Canada.
This project was supported by an operating grant from the Canadian Institutes of Health Research, Canada. Dr. Quan is supported by a Population Health Investigator Award from the Alberta Heritage Foundation for Medical Research, Edmonton, Alberta, Canada, and by a New Investigator Award from the Canadian Institutes of Health Research.
Reprints: Carolyn De Coster, PhD, Quality, Safety and Health Information, Calgary Health Region, Northwest II, 4520 16th Avenue NW, Calgary, Alberta, Canada T3B 0M6. E-mail: Carolyn.DeCoster@calgaryhealthregion.ca.