Adaptation and validation of the Charlson Index for Read/OXMIS coded databases

BMC Fam Pract. 2010 Jan 5:11:1. doi: 10.1186/1471-2296-11-1.


Background: The Charlson comorbidity index is widely used in ICD-9 administrative data, however, there is no translation for Read/OXMIS coded data despite increasing use of the General Practice Research Database (GPRD). Our main objective was to translate the Charlson index for use with Read/OXMIS coded data such as the GPRD and test its association with mortality. We also aimed to provide a version of the comorbidity index for other researchers using similar datasets.

Methods: Two clinicians translated the Charlson index into Read/OXMIS codes. We tested the association between comorbidity score and increased mortality in 146 441 patients from the GPRD using proportional hazards models.

Results: This Read/OXMIS translation of the Charlson index contains 3156 codes. Our validation showed a strong positive association between Charlson score and age. Cox proportional models show a positive increasing association with mortality and Charlson score. The discrimination of the logistic regression model for mortality was good (AUC = 0.853).

Conclusion: We have translated a commonly used comorbidity index into Read/OXMIS for use in UK primary care databases. The translated index showed a good discrimination in our study population. This is the first study to develop a co-morbidity index for use with the Read/OXMIS coding system and the GPRD. A copy of the co-morbidity index is provided for other researchers using similar databases.

Publication types

  • Historical Article
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Clinical Medicine / classification
  • Comorbidity*
  • Databases, Factual
  • Family Practice*
  • History, 20th Century
  • Humans
  • Logistic Models
  • Mortality*
  • Primary Health Care / classification
  • Proportional Hazards Models
  • Software
  • Vocabulary, Controlled* / history