Background: Different methods for changing blood test-ordering behavior in primary care have been proven effective. However, randomized trials comparing these methods are lacking.
Objective: To compare the effect of two versions of BloodLink, a computer-based clinical decision support system, on blood test ordering among general practitioners.
Design: Randomized trial.
Setting: 44 practices of general practitioners in the region of Delft, the Netherlands.
Participants: 60 general practitioners in 44 practices who used computer-based patient records in their practices.
Intervention: After stratification by solo practices and group practices, practices were randomly assigned to use BloodLink-Restricted, which initially displays a reduced list of tests, or BloodLink-Guideline, which is based on the guidelines of the Dutch College of General Practitioners.
Measurements: Average number of blood tests ordered per order form per practice.
Results: General practitioners who used BloodLink-Guideline requested 20% fewer tests on average than did practitioners who used BloodLink-Restricted (mean [+/-SD], 5.5 +/- 0.9 tests vs. 6.9 +/- 1.6 tests, respectively; P = 0.003, Mann-Whitney test).
Conclusions: Decision support based on guidelines is more effective in changing blood test-ordering behavior than is decision support based on initially displaying a limited number of tests. Guideline-driven decision support systems can be effective in reducing the number of laboratory tests ordered by primary care practitioners.