Economic evaluation The societal perspective was used to calculate direct medical costs associated with the treatment in both study groups. Costs were assessed in 2002 euros. Costs per patient were calculated by multiplying resource use by the unit costs. Resource use during hospital stay for diagnostic and therapeutic interventions, consultations of medical or paramedic specialists and antibiotic use was measured. Resource use outside the hospital was evaluated using questionnaires which recorded contacts with general practitioners, specialists, extra diagnostic procedures, use of medication, readmissions, home care and other disease-related costs. Additional costs associated with specific diagnostic tests were based on tariffs. Costs of hospital stay, diagnostic procedures and specialist consultations, were calculated using unit costs as determined within the realm of the Dutch guidelines for pharmaco-economic analyses 25. Costs for readmissions and reinfections were assessed specifically for the study cohort and included costs for extra diagnostic procedures, treatment and hospitalizations. Costs of antibiotics prescribed were estimated using Dutch 2002 formulary cost-prices 26