Estimation of direct cost and resource allocation in intensive care: correlation with Omega system

Objective:An instrument able to estimate the direct costs of stays in Intensive Care Units (ICUs) simply would be very useful for resource allocation inside a hospital, through a global budget system. The aim of this study was to propose such a tool. Design: Since 1991, a region-wide common data base has collected standard data of intensive care such as the Omega Score, Simplified Acute Physiologic Score: length of stay, length of ventilation, main diagnosis and procedures. The Omega Score, developed in France in 1986 and proved to be related to the workload, was recorded on each patient of the study Setting: Eighteen ICUs of Assistance Publique-Hopitaux de Paris (AP-HP) and suburbs. Patients: 1) Hundred twenty-one randomly selected ICU patients, 2) 12,000 consecutive ICU stays collected in the common data base in 1993. Measurements: 1) On the sample of 121 patients. medical expenditure and nursing lime associated with interventions were measured through a prospective study. The correlation between Omega points and direct costs was calculated, and regression equations were applied to the 12,000 stays of the data base, leading to estimated costs. 2) From the analytic accounting of AP-HP, the mean direct cost per stay and per unit was calculated, and compared with the mean associated Omega score from the data base. In both methods a comparison of actual and estimated costs was made. Results: The Omega Score is strongly correlated to total direct costs, medical direct costs and nursing requirements. This correlation is observed both in the random sample of 121 stays and on the data base' stays. The discrepancy of estimated costs through Omega Score and actual costs may result from drugs: blood product underestimation and therapeutic procedures not involved in the Omega Score. Conclusions: The Omega system appears to be a simple and relevant indicator with which to estimate the direct costs of each stay, and then to organise nursing requirements and resource allocation.