Diagnosis of venous thromboembolism From the 9th ICEM Edinburgh 2002

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

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

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

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

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

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

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

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

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

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