DEEP VEIN THROMBOSIS
Cary Gross, M.D.
WEEK 2: 01/10 – 01/14/05
Learning Objectives:
1. How to evaluate a patient with suspected DVT
2. How to incorporate D-dimers into the clinical decision making process
3. Which patients are candidates for outpatient therapy of DVT
CASE ONE:
Mrs. Z, a 44-year-old woman without significant PMH, presents for an urgent visit with
left leg swelling of two days duration. She takes no medications and reports moderate leg
pain but no chest pain, shortness of breath, or palpitations.
Questions:
1. What is the differential diagnosis of unilateral leg swelling?
The differential diagnosis for unilateral leg swelling includes both local and systemic
processes. Local processes include superficial thrombophlebitis, ruptured popliteal
(Baker’s) cyst, calf injury (with accompanying hematoma), asymmetric venous
insufficiency, and other knee injuries. Systemic problems can include CHF, drug-related
edema, or lymphedema – although all of these are usually symmetric.
2. What additional questions would you ask her, in order to help you to assess her
probability of having a deep vein thrombosis (DVT)?
There are many risk factors for venous thromboembolism, including:
Inherited Coagulopathy – patients should be asked about family history of “blood clots,”
multiple miscarriages, rheumatic disease, or prior DVT/PE.
Acquired Coagulopathy – patients should be asked about:
a. Cancer risk
i.
Are they up to date on their screening tests?
ii. Family history of cancer?
iii. Any cancer “warning” signs/symptoms (i.e. change in
bowel habits, possible breast lump, bony pain, etc.)?
b. Pregnancy - could she be pregnant?
c. Chronic conditions that predispose to clots
i. CHF (i.e. inquire about CHF symptoms in this patient)
ii. Medication use (HRT, OCPs, Tamoxifen…)
iii. Obesity
iv. Stroke
Situations/Exposures
a. Recent Immobilization
b. Recent surgery
c. Trauma
CASE ONE CONTINUED:
She reports that she has no family history of blood clots to her knowledge and that she is
not pregnant. She denies any “warning signs” of cancer, and she is up to date on her
cancer screenings (mammogram and pap smear). She denies any family history of
colorectal cancer so she is not yet due for her colorectal cancer screening. She denies
recent immobilization or trauma.
Her exam is significant for a minimally swollen right calf, measuring 1cm wider in
circumference than the left. There is no edema or skin changes; no masses/cords are
palpable. The thighs are symmetric, and no superficial veins are noted.
3. What is the probability that this patient has a DVT?
Preceptors, have the residents estimate the (adapted) Wells score for this patient, using
Table 1 from the Annals article (page 788):
Attribute
Active Cancer
Paralysis/Recent Cast
Major surgery/bedridden >3 days
Tenderness localized to deep veins
Calf and thigh swollen
Calf swelling >3cm asymmetric
Pitting edema in symptomatic leg
Nonvaricose superficial veins
Alternative diagnosis at least as likely
TOTAL
4. How do you interpret this score?
0 = low pretest probability
Points
1
1
1
1
1
1
1
1
-2
Mrs.Z’s
Score
0
0
0
0
0
0
0
0
0
0
5. What other tests would you obtain?
None. A recent article by Bates, et al. in the Annals of Internal Medicine describes the
strategy to incorporate D-dimer with clinical suspicion of DVT in order to determine
whether people need further testing. In this study, the authors use an adaptation of the
Wells criteria (as outlined in the table above) to identify which patients had low or
moderate pre-test probability for DVT. All of these patients then had a D-dimer test,
which is relatively sensitive but not specific for DVT. Patients who had a negative Ddimer test had no further testing or intervention. Of the 283 patients who were followed
up for three months after their initial presentation, only one of them had an actual DVT.
The authors concluded that in these low-risk patients a negative D-dimer test essentially
rules out a DVT and no further testing is necessary.
Preceptors - please review Table 3 with the learners so they can understand how the Ddimer test can change their management. It is important to note that among patients with
a low pre-test probability, positive D-dimer was associated with a 17% prevalence of
DVT. In the same low probability group, a negative D-dimer was associated with a 0%
prevalence of DVT (0 of 193). Hence, in our patient who has a low pre-test probability
and a low D-dimer, no further follow-up is necessary. The patient should be informed of
potential signs and symptoms of DVT or PE and instructed to return to the clinic should
they occur.
CASE TWO:
Assume a different patient comes, with the exact same presenting complaint and past
medical history. And let’s assume her name is Ms. W. The only difference in the
presentation of Ms. W is that she reports that she had the “flu” about one week ago, and
was in bed for 4-5 days.
Additionally, her exam is significant for a swollen and tender right calf, measuring 3cm
wider in circumference than the left. There is pitting edema on the right lower extremity,
extending to the interior calf. There is no change in the skin, and no masses/cords are
palpable. The thighs are symmetric, and no superficial veins are noted.
6. What is the probability that this patient has a DVT?
Preceptors – have the residents estimate the (adapted) Wells score for this patient, using
Table 1 from the Annals article (page 788):
Attribute
Active Cancer
Paralysis/Recent Cast
Major surgery/bedridden >3 days
Points
1
1
1
Mrs. Z’s
Score
0
0
1
Tenderness localized to deep veins
Calf and thigh swollen
Calf swelling >3cm asymmetric
Pitting edema in symptomatic leg
Nonvaricose superficial veins
Alternative diagnosis at least as likely
TOTAL
1
1
1
1
1
-2
0
0
1
1
0
0
3
7. How do you interpret this score?
>2: high pretest probability
8. You check a D-dimer, and it is negative. What other tests would you obtain?
A Doppler ultrasound of the lower extremity. Given the high index of suspicion, you need
to further evaluate this patient in order to comfortably rule out a DVT. Some studies
have suggested that the negative predictive value of D-dimer is only ~80% among
patients with a high pretest likelihood of DVT.
9. You obtain a compression (Doppler) ultrasound and the results are:
a. Negative – does the patient require further workup?
Traditionally, a negative Doppler exam in an outpatient requires some additional
evaluation. Patients are instructed to follow-up in 5-7 days for a repeat Doppler
examination to ensure that a DVT was not missed or that a thrombosis in the calf,
which is frequently undetected by Doppler ultrasound, has not extended
proximally into the thigh.
However, now that D-dimers are available, some studies have suggested that
repeat ultrasound may not be required. In one study, 148 patients with a
moderate-to-high clinical probability of a DVT and normal D-dimers and
negative ultrasound at baseline were followed for three months without a second
ultrasound. None of these patients developed a DVT during the follow-up period.
Hence, it is an acceptable strategy to withhold further testing and follow the
patient closely at this point. However, if your index of suspicion remains high,
one could still consider further evaluation (i.e. repeat ultrasound).
b. Positive, and the patient reports that she has two kids at home and really
does not want to be admitted to the hospital. What do you tell her?
The question about whether patients with an acute DVT can be treated as an
outpatient has been addressed by several large clinical trials. The take-home
point is that outpatient treatment with low molecular weight heparin and warfarin
is a safe and effective approach. However, patients with chronic illness or other
risk factors for bleeding, such as severe systemic hypertension, recent strokes,
spinal cord injury, endocarditis, or pericarditis, should probably be monitored as
inpatients. See Table 3 in the accompanying review article (Yusen et al).
Patients who have these risk factors for bleeding may benefit from inpatient
observation during the initial treatment phase of anticoagulation. It is important
to continue the LMWH until the INR in the therapeutic range (2-3). Patient
should be started on 5 mg of warfarin daily, and the INRs can be checked every
other day in the initial period.
References:
1. Bates, SM. et al., A diagnostic strategy involving a quantitative latex d-dimer assay
reliably excludes deep venous thrombosis. Ann Internal Med. 2003: 138: 787-94.
2. Yusen, RW. and Gage B.F., Outpatient treatment of acute venous thromboembolic
disease. Clinics in Chest Medicine. 2003: 24: 49-61.
Additional References:
1. Lee AY et al. Ann Intern Med. 1999: 131: 417-23.
2. Tick LW et al. Am J Med. 2002: 113:630-5.