[An operating model for assessing the practical efficacy of screening tests: the case of amblyopia]

Standard for assessing the efficacy of screening programs are at present well-established. Nevertheless, the effectiveness of screening programs can reduced by several factors in real world conditions. The aim of this work is to check the feasibility of an operational model for the practical evaluation of the effectiveness of screening programs. In this model seven critical points are defined (recruitment, screening test sensitivity, access to diagnostic services, diagnosis, compliance to follow-up, treatment compliance, therapy) and their contribution to the reduction of potential effectiveness is calculated. For each point consequent problem(s) and possible solutions are predefined. The model was tested with the results of the screening program for amblyopia of the Community Health Service of USL 32 Treviglio (BG) assuming 40% and 97% sensitivity of the screening test. For this screening the reduction of effectiveness at the seven critical points ranged from 0 to 60%, with a total reduction of effectiveness to 15.6-37.8%. The operational model was used to identify causes of this reduction. This kind of analysis is proposed as a tool for evaluation and improvement of the effectiveness of efficacious screening program.