Single Ultrasound May Rule Out DVT During, After Pregnancy

Larry Hand

April 24, 2012

April 24, 2012 — A single ultrasound test may rule out a diagnosis of deep-vein thrombosis (DVT) in pregnant and postpartum women, for whom accuracy of diagnosis is critical but sometimes difficult to achieve, according to an article published online today in the British Medical Journal.

Grégoire Le Gal, MD, from the University of Brest in France, and colleagues conducted a prospective outcome study to evaluate the safety of using a single complete compression ultrasonography exam in 210 women referred for suspected DVT to 2 tertiary care centers and 18 private practices in France and Switzerland between January 2006 and June 2009.

Of 177 women thought not to have DVT and who received no full-dose anticoagulant therapy, only 2 were later confirmed to have developed DVT during follow-up. Of those 2 cases, the researchers write that just 1 was clearly attributable to failure of initial compression ultrasonography.

They did diagnose DVT in 22 (10.5%) of the overall 210 women, "which is lower than usually observed in venous thromboembolic diagnostic studies in Europe. However, the proportion of confirmed venous thromboembolic disease is usually lower in pregnant women, which has been related to a lower threshold for clinical suspicion." the researchers write.

"[T]he three month thromboembolic rate in patients left untreated on the basis of a negative single complete compression ultrasonography result was 2/177 (1.1%, 95% confidence interval 0.3% to 4.0%), in pregnant women was 2/145 (1.4%, 0.4% to 4.9%) and in postpartum women was 0/32 (0.0%, 0.0% to 10.7%)," the researchers write.

The researchers followed the women with negative complete compression ultrasonography test results through 3 months postpartum. At that point, the women were seen in the clinic or interviewed by study staff by telephone and asked about any symptoms "suggestive of veinous thromboembolism." Of the 210 women, 43 were in the postpartum period, 20 were in the first trimester of pregnancy, 51 were in the second trimester, and 96 were in the third trimester. The mean age was 33 years (range, 28 - 37 years).

The researchers write that their results are in line with results reported after the reference test, normal phlebography, in nonpregnant women and with data from a previous study on ultrasonography. They cited limitations of their study, including a relatively small study population, although it was among the largest of pregnant and postpartum women, which could explain a wide confidence interval.

"[W]e cannot exclude that diagnostic exclusion on the basis of a single complete compression ultrasonography result has a higher failure rate than diagnostic strategies for deep vein thrombosis in non-pregnant patients," the researchers write. "If possible, larger studies should be conducted to provide narrower estimates of this failure rate."

They write, however, that their study design was an important step in the validation of diagnostic strategies.

In conclusion, they write, "Our study shows that single complete compression ultrasonography might safely rule out the diagnosis of deep vein thrombosis in pregnant and postpartum women. However, the limitations described above as well as the upper limit of the 95% confidence interval around our estimate of the three month risk of a thromboembolic event prevent us from drawing firm conclusions."

The study was supported by grants from the Projet Hospitalier de Recherche Clinique in France and the Swiss National Foundation. The authors have disclosed no relevant financial relationships.

BMJ. 2012;344:e2635. Published online April 24, 2012. Full text

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