[Validating the Adjusted Clinical Groups [ACG] case-mix system in a Spanish population setting: a multicenter study]

To validate the Johns Hopkins ACG case-mix system used in various primary and specialized care centers attending a defined population in Spain.

A retrospective, multicenter study was carried out by applying the ACG case-mix system to the clinical records of patients attending five primary care teams and two hospitals over a 1-year period in 2005. The main measurements were dependent variables (visits, episodes, primary care costs, and total costs), and morbidity. The determination coefficient (R2; p<0.05) was used to measure the explained variability.

A total of 81,873 patients were included with a mean (standard deviation) number of 4.8 (3.5) episodes and 8.0 (8.1) visits/patient/year. The explained variance (R2) of ACG classification was 73.1% (75.5% log transformation) for episodes, 43.2% (54.0% log transformation) for visits, 19.6% (54.8% log transformation) for primary care costs, and 22.7% (48.3% log transformation) for total costs (p<0.001).

The ACG system classified a defined population on the basis of morbidity and individual resource consumption. Moreover, the ACG system was useful to assess the clinical (comorbidity) and economical information of each center.