Transcript Objective Testing for DVT

Radiology 2005 237: 348-352
Presented by Intern邱宏智
Objective
• To establish the safety of withholding
anticoagulation therapy after negative
findings at a complete lower limb
ultrasonographic (US) examination of the
symptomatic leg for suspected deep
venous thrombosis (DVT).
Deep vein
thrombosis
• Deep venous thrombosis (DVT) affects
about 84 per 100 000 people each year
• Untreated DVT is associated with a high
risk of pulmonary embolism (PE)
• Postthrombotic or postphlebitic syndrome
• False diagnosis of DVT results in
unnecessary anticoagulant therapy, which
is associated with a risk of bleeding
Introduction
• Objective testing for DVT is essential because
clinical assessment alone is unreliable
• Ultrasonographic (US) examination limited to the
common femoral vein, superficial femoral vein,
and popliteal vein, with compressibility of the
vein serving as the sole criterion for diagnosis,
has been the reference standard for diagnosis of
symptomatic lower limb DVT
Introduction
• This limited proximal US examination has nearly
100% sensitivity and specificity for proximal DVT,
as measured with contrast venography
• However, the accuracy of US in the detection of
isolated calf DVT is lower
• Since calf DVT can propagate proximally in onethird of cases, a second US examination is
strongly recommended within 5–7 days to
exclude DVT
• To establish the safety of withholding
anticoagulation therapy after negative
findings at a complete lower limb
ultrasonographic (US) examination of the
symptomatic leg for suspected deep
venous thrombosis (DVT).
Materials and
methods
• Prospective study
• 542 consecutive ambulatory patients with
suspected symptomatic lower limb DVT
• Emergency department of a tertiary
hospital
• a latex agglutination
immunochromatographic D-dimer assay
Objective Testing for
DVT
• Complete real-time B-mode US
examination with color Doppler flow
analysis
• High-spatial-resolution linear-array
transducers with variable frequency (6–8
MHz) probes
• Patients were lying in the supine position,
with the symptomatic leg externally rotated
and slightly flexed at the knee.
• From the level of the inguinal ligament to
the medial malleolus.
• The common femoral vein, superficial
femoral vein, popliteal vein and trifurcation,
and all three deep calf vein sets were
examined.
• Compressibility of these veins was
assessed at 2–3-cm intervals in the
transverse plane.
Superficial femoral vein
• Noncompressibility of a segment of the
veins was the sole criterion for diagnosis of
DVT.
• Doppler examination of these veins was
performed for the purpose of acquiring
supplemental information (only as map
road)
• Anticoagulation therapy was withheld if the
US findings were negative.
Compression
ultrasonography
Follow-up
• After 3 months by telephone, and a
questionnaire was completed for each patient
• The minimum follow-up period of 3 months was
chosen on the basis of previous studies
• Three end point
– the patient was alive and had experienced no
thromboembolic event
– the patient was alive and had evidence of a
thromboembolic event
– the patient died within the follow-up period.
• Patients in whom DVT was suspected because
of new or progressive symptoms were objectively
assessed with a repeat complete lower limb US
examination.
• In patients in whom PE was suspected,
computed tomographic (CT) pulmonary
angiography was performed by using a singledetector row helical CT scanner
• If the CT pulmonary angiogram was negative,
then a complete lower limb US examination was
performed, as described previously.
Result
•
•
•
•
•
413 (78.5%) negative for DVT
113 (21.5%) positive for DVT
243 (46.2%) negative D-dimer
283 (53.8%) positive D-dimer
Negative D-dimer findings, 14 (5.8%) had
positive US findings and 229 (94.2%) had
negative US findings
• positive D-dimer findings, 99(35%) had positive
US findings, and 184 (65%) had negative US
findings.
Positive for DVT
• 64 patients (56.6%) had DVT isolated to
calf veins
• 49 patients (43.4%) had proximal DVT
• 59 men and 54 women,with an average
age of 55.26 years 15.76 (age range, 18–
88 years).
• A total of 26 patients had a history of
previous DVT or PE, and 14 patients had a
history of active malignancy.
• The negative predictive value of a
complete single lower limb US examination
to exclude clinically important DVT is
99.6%
Discussion
• The current diagnostic strategies for lower limb
deep venous thrombosis:
– serial above-knee compression US examinations, with
the second US examination performed 5–7 days after
the initial US examination
– combination of a single above knee compression US
examination with a negative D-dimer assay
– Combination of pretest probability and twopoint
compression US and venography to exclude DVT
DVT was documented in 3, 17, and 75 percent of patients with low,
moderate, or high pretest probabilities, respectively.
Lancet 1997 Dec 20-27;350(9094):1795-8.
• If we use above-knee compression US,
serial examination is necessary to detect
propagation of calf vein thrombi proximally.
• Because the prevalence of proximal DVT
in ambulatory outpatients varies from 9%
in the current study to 28% in a study
performed by Bernardi et al ; the rate of
repeat US in up to 90% of patients is of low
clinical efficiency,
• Though a complete lower limb US
examination would take 10–15 minutes
longer than a limited above-knee US
examination, the second above-knee US
study required would consume substantial
resources, present an inconvenience to
patients, and not always be practical
• it is safe to withhold anticoagulation
therapy after a single negative complete
lower limb US study, with only one patient
(0.2%) experiencing a nonfatal PE 4 days
after the initial US examination
• favorable when compared with previous
strategies
• The proportion of isolated calf DVT is 56%
(64 of 113 patients) in our study, which is
greater than the rate observed in other
studies (31%–45%)
• This may be because the general
practitioners referred patients to the
emergency department at an earlier stage
of the disease spectrum than did
physicians in other studies
• Though isolated calf thrombi present a
therapeutic dilemma (ie, whether to start
anticoagulation therapy or not), the sixth
American College of Chest Physicians
consensus conference on antithrombotic
therapy recommends symptomatic isolated
calf DVT be treated with anticoagulant
medications
• Patient body habitus, especially obesity, results
in an inability to obtain technically adequate US
examinations of calf veins
• The D-dimer test results are rarely
negative, with a 500-ng/mL (enzyme-linked
immunosorbent assay D-dimer)
conventional cutoff value in inpatients, and
it does not contribute to the diagnostic
strategy of combining a negative D-dimer
result with results of an above-knee
compression US examination to rule out
DVT
• only the symptomatic leg rather than both
legs with US
• It has been debated whether bilateral US
imaging should be performed in patients in
whom unilateral DVT is suspected
Summary
• In summary, it is safe to exclude clinically
symptomatic lower limb DVT with a single
complete lower limb US examination, and
anticoagulation therapy can be withheld,
with a low failure rate.
• this strategy would save time and be more
convenient for imaging departments if it
were used in ambulatory outpatients with
suspected symptomatic lower limb DVT.
Thanks for your
attention
Differentiation
•
Muscle strain, tear, or twisting injury to the leg — 40 percent
Leg swelling in a paralyzed limb — 9 percent
Lymphangitis or lymph obstruction — 7 percent
Venous insufficiency — 7 percent
Popliteal (Baker's) cyst — 5 percent
Cellulitis — 3 percent
Knee abnormality — 2 percent
Unknown — 26 percent
• Prospective studies have demonstrated that lack of
compressibility of a vein with the ultrasound probe is
highly sensitive (>95 percent) and specific (>95 percent)
for proximal vein thrombosis
• Color flow imaging, in addition to duplex Doppler
ultrasound, is a less demanding study and is also highly
accurate for the diagnosis of above the knee DVT
• In comparison, the presence of an echogenic band,
although sensitive for DVT, has a specificity of only about
50 percent
• The variation of venous size with the Valsalva maneuver
has a low sensitivity and specificity for the presence of
DVT and is not performed in many centers
Compression
ultrasound
• Limitations
– It does not detect isolated thrombi in the iliac veins or superficial femoral
veins within the abductor canal.
– As with impedance plethysmography, the results are limited in patients
with deformities or a plaster cast.
– Serial studies need to be performed when the initial test is negative;
approximately 2 percent of patients with an initially negative ultrasound
develop a positive study when retested seven days later. A single repeat
study that is negative five to seven days after an initial negative study
predicts a less than 1 percent likelihood of venous thromboembolism
over months of follow-up
– Patients with pelvic neoplasms or abscesses may demonstrate isolated
noncompressibility of the femoral vein when thrombosis is absent
– It is less useful than impedance plethysmography for recurrent DVT. As
noted above, only 60 to 70 of studies return to normal at one year
compared to over 90 percent with impedance plethysmography
• Extended (complete) lower extremity ultrasound
• routine compression ultrasonography has certain
limitations, two of which are the lack of detection of iliac
vein disease and the need for serial studies, with which
the patient may not comply, if the first is test is negative
and clinical suspicion is high.
• The generalizability of these observations may be limited
because the quality of complete lower extremity
ultrasound studies is operator-dependent
•
•
•
•
Sn = TP / (TP + FN)
Sp = TN / (TN + FP)
PPV = TP / (TP + FP)
NPV = TN / (TN + FN)