Deep vein thrombosis: a third had normal ultrasounds at one year.

Clinical bottom line (level 4)

Around a third of patients with deep vein thrombosis had normal ultrasound scans at one year.
By three years, two thirds of ultrasound scans were normal.

Prandoni et al: Circulation 1993; 88 (1): 1730-1735

Expires May 2003

The study

Prospective cohort study with unblinded, unobjective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: university hospital, Italy

148 patients (aged range 17 to 89 years; mean 61, 53% male) first episode of acute proximal deep vein thrombosis (diagnosed by venogram and ultrasound)
All patients were treated with anticoagulation for three months.

<80% followed for 3 years
Outcomes studied:

ultrasound reverted to normal at 3-6 months

ultrasound reverted to normal at 6-12 months

ultrasound reverted to normal at 12-24 months

ultrasound reverted to normal at 24-36 months

The evidence

outcome	time to outcome	number of patients/total number	% (95% CI)
ultrasound reverted to normal at 3-6 months	3 years	5/24	21% (4.6% to 37%)
ultrasound reverted to normal at 6-12 months	3 years	12/40	30% (16% to 44%)
ultrasound reverted to normal at 12-24 months	3 years	24/48	50% (36% to 64%)
ultrasound reverted to normal at 24-36 months	3 years	24/37	65% (49% to 80%)

Comments

One patient had an isolated calf DVT missed on ultrasound.
Note large loss to follow-up makes results less certain.
Few patients currently have repeat ultrasound scans- would comparison with initial measurement be as effective?

Citation

Prandoni P, Cogo A, Bernardi E, et al: A simple ultrasound approach for detection of recurrent proximal-vein thrombosis. Circulation 1993; 88 (1): 1730-1735

Contributor: Chris Ball and Clare Wotton, May 2000
Reviewer:

_{Clinical Question.}

_Patient	_DVT
_{Intervention or Exposure}	_{prevalence of normal ultrasound scan}
_Outcome	_{at one, two and three years}