Comorbidity indexes from administrative datasets: what is measured?

It is important to factor-in the characteristics of patients that may affect treatment, outcome and resource when making clinical and administrative decisions, plans or policies. For some two and half decades there have been efforts to construct and refine instruments that endeavour to capture the concept of comorbidity. This paper focuses on such comorbidity measures that are derived from diagnoses information recorded in administrative datasets. The pros and cons of the popular weighted Charlson and Charlson-based indexes are discussed. Means to improve the comorbidity indexes are considered including the very concept and definition of comorbidity.