[An analysis of the demand for laboratory tests from primary care in a health area]. / Análisis de la demanda de pruebas de laboratorio desde atención primaria en un área de salud.

OBJECTIVE: To quantify the primary care demand for laboratory tests in a health area and to evaluate the variations in use in relation to the characteristics of the doctors, of organisation and of the population seen. DESIGN: Crossover. SETTING: A health area in the Community of Valencia with 110125 inhabitants. PARTICIPANTS: 89 primary care doctors from the area, with 8612 requests for lab. tests over 12 weeks. MEASUREMENTS AND MAIN RESULTS: All the lab. requests, including determinations (67730), diagnoses, and age and sex of patients, were recorded. Total and health consultations were calculated. The overall demand rate was 356 requests per 1000 inhabitants, with variations in the standardised rates by age of population between Districts (ranging from 242 to 548 per 1000). Lab. tests were requested for 8.6 of every 100 health consultations, with variations of up to three times this number depending on the distance from the laboratory. Women doctors asked for a higher number of determinations per request. whereas more requests were made for male than for female patients. CONCLUSIONS: There are substantial variations in primary care use of the laboratory, which are hard to explain by differences in underlying pathology. Some reasons for variation are organisational, but others remain to be tested. Findings indicate that interventions should be designed to improve the quality of laboratory use. Meanwhile, study of the causes of variations in demand continues.