[Cost at the first level of care]. / Costo en el primer nivel de atención.

OBJECTIVE: To estimate the unit cost of 15 causes of demand for primary care per health clinic in an institutional (social security) health care system, and to determine the average cost at the state level. MATERIAL AND METHODS: The cost of 80% of clinic visits was estimated in 35 of 40 clinics in the social security health care system in the state of Nuevo Leon, Mexico. The methodology for fixed costs consisted of: departmentalization, inputs, cost, weights and construction of matrices. Variable costs were estimated for standard patients by type of health care sought and with the consensus of experts; the sum of fixed and variable costs gave the unit cost. A computerized model was employed for data processing. RESULTS: A large variation in unit cost was observed between health clinics studied for all causes of demand, in both metropolitan and non-metropolitan areas. Prenatal care ($92.26) and diarrhea ($93.76) were the least expensive while diabetes ($240.42) and hypertension ($312.54) were the most expensive. Non-metropolitan costs were higher than metropolitan costs (p < 0.05); controlling for number of physician's offices showed that this was determined by medical units with only one physician's office. CONCLUSIONS: Knowledge of unit costs is a tool that, when used by medical administrators, allows adequate health care planning and efficient allocation of health resources.