1. Diagnosis of venous thromboembolism
From the
9th ICEM
Edinburgh 2002

2. Achieving a pre-test probability score (PTP)
Using the Wells criteria
20% can be expected to have clot on USS
85% proximal
15% distal
Of which 20-30% will propagate distally
Therefore require repeat ultrasound at 1 week

3. Risk calculation for DVT
Active cancer or treatment within 6/12
Paralysis, paresis or cast of leg
Immobilised>3/7 or surgery in last 3/12
Localised tenderness along deep veins
Entire leg swollen
Swelling >3cm
Pitting oedema confined to symptomatic side
Collateral superficial veins distended
Alternative diagnosis likely
1.0
-2.0

4. PTP score and DVT PTP score % with DVT EDIT Study 3 or more High 85 49
1-2
Medium 33 14
Less than 1
low 5
Low 3

5. Note that of the patients with a high probability and a negative USS, 4/25 (16%) had a DVT on venography.

6. D-dimer Breakdown product of fibrin
Forms quickly and persists for days
Available tests are sensitive but not very specific
Negative test can rule out DVT/PE

7. D-dimer assays % sensitivity % specificity Rapid ELISA 80-85 70-90
Automated latex agglutination
90-95
40-90
Whole blood agglutination
95-100
30-60

8. ELISA -ve Simplired –ve & low PTP
Suspected DVT
ELISA -ve Simplired –ve & low PTP
No DVT No DVT

9. Pulmonary embolus Active cancer or treatment in last 6/12
Recent surgery or bedridden
Previous DVT/PE
Haemoptysis
HR>100
Signs/symptoms of DVT
Another diagnosis as likely or more likely than PE
1.0
1.5
3.0
-2.0

10. PTP score and PE PTP % incidence Wells study >6 High 78 64 37.5 2-6
Number pts
>6
High 78 64
37.5
2-6
Medium 28
339
16.2
<2
Low 3
527
1.3
Wells. Annals of internal medicine 2001 prospective cohort study
Clinical,PTP and DD
No further testing if low PTP and DD negative
VQ scanning if +/- CUS

11. Two studies; patients with negative DD and low PTP:
437 pts – 1 VTE in follow up
759 pts – 1 VTE in follow up
The clinical model appears to be a rational and cost effective approach to VTE diagnosis