Daniel J. Durand, M.D., from Johns Hopkins University in Baltimore, Md., and colleagues identified the 10 most frequently ordered imaging tests in fiscal year 2007. No costs were displayed during a baseline period from Nov. 10, 2008, to May 9, 2009. Costs were displayed only for tests in the active group during a seasonally matched intervention period from Nov. 10, 2009, to May 9, 2010. At the conclusion of the study, the number of orders executed for all tests during both periods was compared.The researchers found that there was no significant difference in the mean utilization change between the active group and the control group (2.8 ± 4.4 percent and −3.0 ± 5.5 percent, respectively; P = 0.10). For the active versus control group, there was no significant difference in the correlation between the cost of the test and the change in utilization. The study had 90 percent power to detect an 11.8 percent difference in mean relative utilization change between groups, on the basis of the observed standard deviations.