If the pretest probability of deep vein thrombosis is low, a normal D-dimer level is enough to rule it out.
To read the full article, go to the Cleveland Clinic Journal of Medicine: http://www.ccjm.org/current-issue/issue-single-view/does-the-patient-need-ultrasonography-of-the-leg-to-evaluate-for-deep-vein-thrombosis/920380017b1df57c1c99c1194c3b136f.html.