Pulmonary Embolism-Deep Vein Thrombosis

Index to Page:

Echocardiographic features of Major Pulmonary Embolism
Major Pulmonary Embolism Therapy
Pretest risk of Deep Vein Thrombosis
Pretest risk of Pulmonary Embolism

D-Dimer

I have reviewed the last 7 years (in 2003) worth of articles from standard journals and have derived the following test characteristics from the data there in (see references).

Sensitivity 98% (88-100)
Specificity 52% (32-75)
Positive Predictive Value 39% (23-61)
Negative Predictive Value 99% (95-100)
Accuracy (true pos + true neg) 61% (47-75)
Prevalence of DVT or PE 24% (9-48)
Likelihood Ratio + 2.04
Likelihood Ratio - 0.03

This generally assumes a negative d-dimer with low probability setting as a negative test. And it assumes a positive d-dimer or medium to high probability setting as a positive test with a complete workup.

What are the implications of these data ?

The negative predictive value for a negative d-dimer with a low probability setting is excellent. It should be good enough to rule out a DVT or PE. There is one caveat here. There have been two studies of DVT in cancer patients with discrepant negative predictive values, one study found a 79% level and the other was at 97%. You may want to be careful in the setting of a cancer patient excluding DVT or PE with a negative d-dimer.

A positive d-dimer tells you to work up the patient more completely. In the setting of a suspicion of DVT the next test would be a leg ultrasound, followed by a venogram in the setting of a high probability of DVT. In the case of a suspected pulmonary embolism the next test would be a ventilation/perfusion scan, followed by a bilateral leg ultrasound, and then possibly angiography or spiral CT or one week follow up.

The positive predictive value is low, so when the d-dimer is positive you will often not find a DVT or PE.

These data seem consistent across prevalence from 9-48% for DVT and PE.

References:

1. Arch Intern Med 2002;162:1880-1884, The clinical usefulness of D-dimer testing in cancer patients with suspected deep vein thrombosis.

2. Arch Intern Med 2002; 162:907-11, Simplification of the diagnostic management of suspected deep vein thrombosis.

3. Arch Intern Med 2002; 162:217-20, The sensitivity and specificity of a red cell agglutination d-dimer assay for venous thromboembolism when performed on venous blood.

4. Ann Intern Med 2001; 135:98-107, Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer.

5. Ann Intern Med 2001; 135:108-11, Management of suspected deep vein thrombosis in outpatients by clinical assessment and d-dimer testing.

6. JAMA 2001; 285:761-68, Diagnostic accuracy of a d-dimer assay and alveolar dead space measurement for rapid exclusion of pulmonary embolism.

7. Ann Intern Med 1999; 131:417-23, Clinical utility of a rapid whole blood d-dimer assay in patients with cancer who present with suspected acute deep vein thrombosis.

8. Lancet 1999; 353:190-95, Non-invasive diagnosis of venous thromboembolism in outpatients.

9. Ann Intern Med 1998; 129:1006-11, Sensitivity and specificity of a rapid whole blood assay for d-dimer in the diagnosis of pulmonary embolism.

DVT (From Lancet 1995; 345:1326-30)

Probabilities will be generated from the following ‘Checklist’. Record the number of ‘major’ and ‘minor’ points, each is worth 1 point in it’s respective category.
Then go to the ‘Clinical Probability’ section and determine whether the patient qualifies as low or high probability.

Checklist

Major Points

___Active cancer (treatment ongoing or within previous 6 months or palliative)

___Paralysis, paresis, or recent plaster immobilization of the lower extremities

___Recently bedridden >3 days and/or major surgery within 4 weeks

___Localized tenderness along the distribution of the deep venous system (either in calf or thigh elicited along the anatomical distribution of the deep vein system)

___Thigh and calf are swollen on measurement

___Calf swelling 3cm> symptom less side (measured 10cm below the tibial tuberosity)

___Strong family hx of DVT ($2 first degree relatives with hx of DVT)

Minor Points

___History of recent trauma ($60 days) in the symptomatic leg

___Pitting edema in the symptomatic leg only

___Dilated superficial veins (non-varicose) in the symptomatic leg only

___Hospitalization within the past six months

___Erythema

Pretest Clinical Probability of DVT

High Probability

$3 major points and no alternative diagnosis

$2 major points and $2 minor points + no alternative diagnosis

Moderate Probability

All combinations not high or low

Low Probability

1 major point + $2 minor points + has an alternative diagnosis

1 major point + $1 minor point + no alternative diagnosis

0 major points + $3 minor points + has an alternative diagnosis

0 major points + $2 minor points + no alternative diagnosis

 

 

Pulmonary Embolism

Wells Rule(From Annals Int Med 2001; 135:98-107)

Uses a clinical point scale that is summed up to generate a score.

Point Scale Scoring System

3.0 points= Measured leg swelling and pain with calf palpation in the deep vein region

1.5 points = Pulse > 100 beats per minute

1.5 points = Immobilization for $3 consecutive days (except to go to bathroom) or surgery in the past 4 weeks .

1.5 points = Previously objectively diagnosed DVT or PE

1.0 points = Hemoptysis

1.0 points = Malignancy (receiving treatment, treatment within 6 months, palliative care)

3.0 points = PE is as likely as or more likely than an alternative diagnosis

 

Pretest Clinical Probability of PE

Score

High >6.0

Medium 2.0-6.0

Low <2.0

Geneva Score (original and simplified) Arch Intern Med 2008;168(19):2131-2136

Original and Simplified Revised Geneva Score
Variable	Original	Simplified
Age >65	1	1
Prior DVT or PE	3	1
Surgery (under anesthesia) or lower limb fracture within 30 days	2	1
Active malignancy (solid or hematologic, currently active or cure <1 year)	2	1
Unilateral leg pain	3	1
Hemoptysis	2	1
Heart Rate, beats/minute
75-94	3	1
>94	2	1
Pain on lower limb deep venous palpation and unilateral edema	4	1

 

Simplified Geneva Score interpretation for Risk of Pulmonary Embolism Always do a D-Dimer if score is <=4
Score	Risk of PE	Prevalence of PE in Population Studied
0	Low	PE=7.7% of population, n = 378
1
2	Intermediate	PE=29.4% of population, n = 629
3
4
5	High	PE=64.3% of population, n = 42
6
7

Echocardiographic Findings of Major Pulmonary Embolism

Right ventricular dilatation and hypokinesis
Interventricular septal flattening and paradoxical septal motion
Reduced LV distensibility during diastole, which results in increased left atrial contribution to LV filling and an A wave > E wave
Pulmonary hypertension on Doppler imaging
Direct visualization of embolism- rarely seen

Major Pulmonary Embolism Therapy

Thrombolysis with 100 mg tissue plasminogen activator continuous infusion over 2 hours

Embolectomy- surgical

[botom.htm]