Computerized alert reduced D-dimer testing in the elderly.

Objective: To assess the effect of a targeted age-specific computerized alert to reduce D-dimer testing in elderly patients.

Study Design: A single-crossover cluster randomized trial of computerized alerts during physician order entry involving 8 ambulatory care clinics in a group-model integrated care delivery system.

Methods: The rate of completed D-dimer tests per 1000 patient visits, ratio of completed venous ultrasonography to completed D-dimer tests, and rate of completed venous ultrasonography per 1000 patient visits.