To the Editor: Dr Bernardi and colleagues1 compared the safety of excluding DVT by serial 2-point ultrasonography to whole-leg color-coded Doppler ultrasonography. Of particular interest was the distribution and timing of the venous thromboembolic events during the 3-month follow-up period in the 2 study groups.
In the serial 2-point ultrasound strategy, 3 of 7 cases (43%) of thrombosis were diagnosed within the first 2 weeks after inclusion, whereas in the whole-leg ultrasound group, only 1 of 9 cases (11%) occurred in the first 2 weeks. We hypothesize that the former 3 events were caused by progression of a distal DVT, which was initially identified by the D-dimer test but later missed by serial compression ultrasonography. Conversely, in the whole-leg cohort the incidence of thrombosis later in the follow-up period is higher compared with the serial 2-point ultrasound group.
Klok FA, Tan M, Huisman MV. Ultrasound-Based Diagnostic Strategies for Deep Vein Thrombosis. JAMA. 2009;301(9):933-935. doi:10.1001/jama.2009.185