Congenital heart disease: interrelation between German diagnoses-related groups system and Aristotle complexity score.

OBJECTIVES The Disease-Related Groups (DRGs) system postulates that inpatient stays with similar levels of clinical complexity are expected to consume similar amounts of resources. This, applied to surgery of congenital heart disease, suggests that the higher the complexity of procedures as estimated by the Aristotle complexity score, the higher hospital reimbursement should be. This study analyses how much case-mix index (CMI) generated by German DRG 2009 version correlates with Aristotle score. METHODS A total of 456 DRG cases of year 2008 were regrouped according to German DRG 2009 and related cost-weight values and overall CMI evaluated. Corresponding Aristotle basic and comprehensive complexity scores (ABC and ACC) and levels were determined. Associated surgical performance (Aristotle score times hospital survival) was estimated. Spearman 'r' correlation coefficients were calculated between Aristotle scores and cost-weights. Goodness of fit 'r(2)' from derived regression was determined. Correlation was estimated to be optimal if Spearman 'r' and derived goodness of fit 'r(2)' approached 1 value. RESULTS CMI was 8.787 while mean ABC and ACC scores were 7.64 and 9.27, respectively. Hospital survival was 98.5%: therefore, surgical performance attained 7.53 (ABC score) and 9.13 (ACC score). ABC and ACC scores and levels positively correlated with cost-weights. With Spearman 'r' of 1 and goodness of fit 'r(2)' of 0.9790, scores of the six ACC levels correlated at best. The equation was y = 0.5591 + 0.939x, in which y stands for cost-weight (CMI) and x for score of ACC level. CONCLUSIONS ACC score correlates almost perfectly with corresponding cost-weights (CMI) generated by the German DRG 2009. It could therefore be used as the basis for hospital reimbursement to compensate in conformity with procedures' complexity. Extrapolated CMI in this series would be 9.264. Modulation of reimbursement according to surgical performance could be established and thus 'reward' quality in congenital heart surgery.