The use of direct mail to increase clinician knowledge: an intervention study.

A probability sample of American general practitioner dentists, 40 years of age or older, in solo private practice, was the target of two direct mail interventions offered at two different times, to test whether knowledge regarding prophylaxis of patients at risk for infective endocarditis could be improved. Tests of knowledge were responses in a mail questionnaire to clinical vignettes, designed to elicit the content of antibiotic regimens used for patients at risk. The research design enabled detection of (1) the effect of the interventions; (2) the differences in their effect; (3) the attenuation of their effect; and (4) the effect of time. Where baseline knowledge was low, it was improved and did not rapidly disappear. Both mail interventions were equally effective, in most instances, and there was no attenuation of the interventions' effect and no effect of time on the control groups' knowledge over a 4 1/2 month period. The results suggest that it is possible to improve clinicians' knowledge of expert recommendations through direct mail intervention.