Background and objectives: Adjustment for comorbidity is an essential component of any observational study comparing outcomes. We evaluated the validity of the Charlson comorbidity score based on ICD-10 codes in patients undergoing urological cancer surgery within an English administrative database.
Study design and setting: Patients who underwent radical urological cancer surgery between 1998 and 2002 in the English National Health Service were identified from the Hospital Episode Statistics database (N = 20,138). ICD-9-CM codes defining comorbid diseases according to the Deyo and Dartmouth-Manitoba adaptations of the Charlson comorbidity score were translated into ICD-10 codes.
Results: Charlson scores derived by the ICD-10 translation of the Deyo and Dartmouth-Manitoba adaptations were identical in 16,623 patients (83%; kappa = .63). For both adaptations, ICD-10 scores increased with age, were higher in patients admitted on an emergency basis, and predicted short-term outcome. Addition of either the ICD-10 Charlson Deyo or Dartmouth-Manitoba score to risk models containing age and sex to predict in-hospital mortality resulted in a better model fit but only in small improvements of the predictive power.
Conclusion: The ICD-10 translations of the Deyo and Dartmouth-Manitoba adaptations performed similarly in risk models predicting hospital mortality following urological cancer surgery. Adjustment for comorbidity over and above age and sex alone does not seem to provide a large improvement.