Background: Diagnosis of Deep Vein Thrombosis (DVT) involves the combination of a clinical prediction model, D-dimer testing and radiographic imaging. Practice guidelines recommend initial diagnostic test with compression duplex ultrasound of the lower extremities in patients with a high clinical pretest probability for DVT. A negative initial ultrasound is further stratified with a d-dimer assay and/or one week follow up ultrasound.

Aims: To investigate the local pattern of practice of performing compression ultrasound one-week following initial presentation in patients with suspected DVT whose initial ultrasound study is negative. The project quantifies the number of one-week ultrasound studies performed at hospitals in the Nova Scotia Health Authority Central Zone and identifies the proportion of one-week ultrasounds that convert to positive.

Methods: Patients who received two compression ultrasounds of the extremities within a timeframe of 5 to 10 days between January 2012 and December 2016 were screened.

Results: 639 sets of paired ultrasounds of the extremities were screened. Paired ultrasounds with discordant laterality or of the upper extremities were excluded. 376 pairs of studies with negative initial ultrasounds from 362 patients were included for analysis. Of these 376 studies, 2.9% (95% CI: 1.1 – 4.8%) from 11 patients were then found to have a proximal DVT at 1 week follow up. 7 studies reported superficial thrombophlebitis, 5 as below knee DVT and 2 as chronic thrombotic changes at one week follow up. Stratification by d-dimer testing is shown where available. Results are shown in Figure 1.

Conclusions: In this group of patients who underwent serial ultrasonography of the lower extremities for suspected DVT, 11/376 with negative initial ultrasounds were positive for DVT at one week. The recommended practice of performing serial ultrasounds allows for detection of the development of DVT in a selected population.

[Figure 1 – Results of serial ultrasounds performed between Jan 2012 and Dec 2016 in the Nova Scotia Health Authority Central Zone.]

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/serial-ultrasounds-in-deep-vein-thrombosis-diagnosis-a-single-centre-retrospective-review/