Diagnosis of Lower-Extremity DVT (Guideline) - PulmCCM
Advertisement
May 212012
 
Diagnosis of Deep Venous Thrombosis (DVT) of the Lower Extremity
from the ACCP / Chest Guidelines, 9th Ed.

PulmCCM is not affiliated with ACCP; this commentary is appropriate only for those who have read the original ACCP document, which is linked below.

Diagnosis of DVT of the leg should incorporate these principles of safety:

  • Reducing overall false-negatives to 2% or less (as defined by symptomatic DVT or PE within 3-6 months after a negative test);
  • Reducing the risk of fatal PE after testing to <0.1% (1 in 1,000);
  • Reducing the risk of fatal hemorrhage due to anticoagulation to <0.1% (1 in 1,000).

The ACCP recommendations are in essence the “outputs” of the authors’ own Bayesian risk model, into which they plugged in assumptions for true DVT prevalence, bleeding risk, risk for death from recurrent PE, etc., all obtained (wherever possible) from the rates of these events observed in previous clinical trials. Authors could not always assure themselves of meeting the above safety / surety standards, in which case they downgraded the recommendations’ strength.

These ACCP recommendations are for nonpregnant patients with a suspected first DVT of the lower extremity; the Chest guidelines for diagnosis of a first leg DVT in pregnant women and the diagnosis of recurrent DVT will be reviewed soon.

ACCP Recommendation: Risk-Stratify Patients for Likelihood of DVT

Rather than pursuing a standard approach for all patients with suspected DVT, risk-stratify patients as low, intermediate, or high pretest probability for DVT, authors advise (Grade 2B, suggestion based on moderate-strength evidence). While acknowledging its limitations, they cautiously endorse using the Wells score for this, which provides risk assessment as follows:

Wells Score  Prob. of DVT
Low 5%
Moderate 17%
High 53%
Testing For Patients with a LOW Pretest Probability for DVT (figure)

ACCP recommendations for testing of patients with a low pretest probability for a first DVT of the leg advise checking either:

  • Moderately sensitive D-dimer (whole-blood or “latex semi-quantitative,” sensitivity ~85%);
  • Highly sensitive D-dimer (ELISA-based or “quantitative latex or immunoturbidimetric,” sensitivity ~95%);
  • Compression ultrasound of the proximal leg veins (rather than whole-leg ultrasound).

They suggest using D-dimer preferentially over compression ultrasound of the proximal veins as the initial test (Grade 2B/2C).

If D-dimer is negative in a patient with a low pretest probability for DVT, no further testing is recommended (Grade 1B, strong recommendation based on moderate strength evidence).

If D-dimer is positive in a patient with low pretest probability for DVT, ACCP’s recommendations are to check compression ultrasound of the proximal leg veins, rather than whole-leg ultrasound (Grade 2C) or venography (Grade 1B).

If compression ultrasound of the proximal leg veins is positive for DVT, treat for DVT without further testing (Grade 2C).

Why the ACCP recommendation for compression ultrasound of the proximal leg veins rather than whole-leg ultrasound for patients with low pretest probability for DVT? Whole-leg ultrasound is more likely to identify an isolated calf-vein DVT, which in these patients has a low chance of propagating proximally and becoming a dangerous clot. Identifying and treating likely-harmless calf vein DVTs in these patients carries an excess risk of serious bleeding from anticoagulation, authors say.

Testing For Patients with a MODERATE Pretest Probability for DVT (figure)

ACCP recommendations for testing of patients with a moderate pretest probability for a first DVT of the leg advise checking either:

  • Highly sensitive D-dimer,
  • Compression ultrasound of the proximal leg veins, or
  • Whole-leg ultrasound.

ACCP suggests using highly-sensitive D-dimer over ultrasound as the initial test (Grade 2C), unless the patient has a comorbid condition that would likely elevate the D-dimer level (cancer, disseminated intravascular coagulation, older age, infection, pregnancy, recent trauma or surgery, inflammatory process, atrial fibrillation, and/or stroke), in which case ultrasound would be better as the first test.

If a highly sensitive D-dimer is NEGATIVE in a patient with moderate pretest probability for a first DVT of the leg, the ACCP recommendation is that no further testing be pursued (Grade 1B).

If a highly sensitive D-dimer is POSITIVE in a patient with moderate pretest probability for a first DVT of the leg, perform compression ultrasound of the proximal leg veins, or the whole-leg. (Grade 1B).

If a first compression ultrasound of the proximal leg veins is NEGATIVE, ACCP recommends one can either:

  • Repeat the compression ultrasound in one week. If it’s negative, no further testing is needed.
  • Check a moderate/high sensitivity D-dimer. If the D-dimer is negative, no further testing is recommended. If the D-dimer is positive, recheck compression ultrasound in one week as above.

If whole-leg ultrasound is chosen and is NEGATIVE, no further testing is recommended (no repeat ultrasound, D-dimer, or venography are advised, all Grade 1B).

If compression ultrasound or whole-leg is POSITIVE for proximal DVT at any point, ACCP recommends treating for DVT without further testing.

If whole-leg ultrasound is only positive for isolated distal (calf vein) DVT, ACCP suggests serial ultrasounds to ensure the DVT does not propagate proximally, rather than treating with anticoagulation (Grade 2C). This decision must be individualized: patients with significant symptoms, or who are averse to the hassle and anxiety of repeated ultrasound testing, may prefer anticoagulation over serial ultrasounds.

Testing For Patients with a HIGH Pretest Probability for DVT (figure)

ACCP recommendations for testing of patients with a HIGH pretest probability for a first DVT of the leg advise checking either:

  • Compression ultrasound of the proximal leg veins, or
  • Whole-leg ultrasound.

If any ultrasound test is positive at any point, ACCP guidelines advise to treat for DVT without further testing.

For those with a negative whole-leg ultrasound for DVT, no further testing is suggested (Grade 2B).

For those with a negative compression ultrasound of the proximal leg veins, one can either:

  • Repeat ultrasound in one week (either compression ultrasound of the proximal leg veins, or whole-leg ultrasound). If it is negative for DVT, no further testing is recommended.
  • Check a high-sensitivity D-dimer. If it is negative, no further testing is recommended. If the D-dimer is positive, repeat compression ultrasound in one week is recommended; if it is negative, no further testing is recommended.
  • Perform venography – which is no longer available at most centers. There is an insufficient body of evidence to conclude whether CT venography (which is widely available) is an adequate substitute for invasive venography.

In patients with a high pretest probability for DVT, don’t use D-dimer (even a high-sensitivity assay) as a stand-alone test to rule out DVT (Grade 1B).

Testing For DVT When Risk-Stratification Isn’t Done

If risk stratification is not done, the ACCP recommendation is to check compression ultrasound of the proximal leg veins or whole-leg ultrasound, rather than D-dimer, as the initial test (Grade 2B). ACCP’s recommended additional testing steps for patients not risk-stratified follow the pattern described in the figure in the original article corresponding generally to the decision-making for patients at moderate-to-high pretest probability for DVT.

Whenever ultrasound is impractical or the test result cannot be trusted (e.g., obesity or leg casting limit visualization), CT venography or magnetic resonance imaging (MR venography or direct thrombus imaging) should be considered.

Bates SM et al. Diagnosis of DVT. Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012;141:e351S-e418S.

Liked this post? Get a weekly email update (no spam, ever), and explore our library of pulmonary and critical care guidelines, practice updates and review articles.

PulmCCM is an independent publication, not affiliated with or endorsed by any other organization, society and/or journal referenced on the website.

  3 Responses to “Diagnosis of Lower-Extremity DVT (Guideline)”

  1. A sound logical approach to acommon difficult clinical prob[em.it may prove difficult to convince a patient tto go for one modality of invesigation rather than the other especially when they are a bit on the informed side .

  2. [...] the consequences can be grave, guidelines published by The College of Chest Physicians stress that the chances of developing DVT/PE following long-distance air travel is still very [...]

  3. It would be useful to have this recommendations in a Graphic format

Leave a Comment