RESUMEN
OBJECTIVE: Our main objective is to analyse to the relationship between the direct cost of a hospitalary discharge and the length of stay controlling for other care variables. METHODS: Analysis of the direct costs of pharmacy, laboratory, pathology and radiology tests of the 21,883 discharged patients in two Barcelona hospitals during 1993, in relationship to care variables contained in the basic minimum data set for discharged patient (BMDSDP). Using both hospital information systems in which are detailed the complete activity carried out and the assignment of unitary costs by means of different methods adapted to the available information, the direct cost is built up for patient and it is assembled by DRG. With the direct cost information and the care variables of the BMDSDP, a simple linear regression (least squared method) is carried out. RESULTS: The average direct cost is up to 31,533 pesetas. The regression by least squared method explains 70% of the variance (R2) and the variables with higher explanatory power are the length of stay and the relative weight of average DRG direct costs, that acts like variable of adjustment. CONCLUSIONS: The variability of the direct cost is explained principally by the length of stay. In addition, the length of stay is also very important on explaining the internal variability of DRG direct cost.