Background: Although outreach visitor interventions have proven to be effective, more detailed studies are needed to understand what elements of interventions work and why. In this study we investigate the determinants of success of an intervention for optimizing cardiovascular preventive care in general practice.
Methods: After baseline measurements and randomization, 62 general practices received a comprehensive intervention program, by means of outreach visitors, lasting 21 months. Data on practice management and preventive activities were gathered at baseline and at postintervention measurements. Key characteristics of the intervention considered possible determinants of success were gathered by questionnaire. The difference between ideal and actual practice in each aspect of organizing cardiovascular preventive care was calculated as a deficiency score. The difference between deficiency scores before and after the intervention were the main outcome measures.
Results: The key characteristic, duration of exposure to an aspect (in months), was positively related to the change in availability of separate clinics and in the amount of teamwork. The improvement in instruments and materials was positively related to the general practitioner's opinion about the given feedback. No relations were found between the key characteristics and changes in record-keeping or follow-up routines.
Conclusions: Although implementation of a comprehensive prevention program is effective, we could not fully disentangle the "black box" of the intervention. The duration of exposure to an aspect of organizing cardiovascular care was the key determinant to success.