A number of approaches and investigations can be used to diagnose thromboembolic disease, which vary depending on the location of the disease. A combination of clinical decision rules and physical testing is frequently involved.
Clinical decision rules can be used to assess the probability of developing a deep venous thrombosis (DVT) or pulmonary embolism (PE). The most commonly used rules are the:
CT can detect pulmonary emboli directly and is the only test that can provide extensive diagnostic information or an alternate diagnosis. Advances in multidetector technology, and the combined use of CT scan and angiography/venography, have markedly improved detection of deep emboli. Because of its sensitivity, pulmonary CT angiography is recommended for the majority of cases of suspected PE. There is evidence to suggest that this test is more cost effective than other diagnostic approaches.
Traditionally, contrast angiography/venography was used as the standard method for evaluating thromboses. However, in recent years, advances in ultrasonography have reduced the need for such invasive procedures. Ultrasonography is not suitable in all cases, however, as its sensitivity is reduced when imaging deeper venous areas.4
In general, contrast venography is still appropriate where patients have experienced prior DVT, or if clinical findings/ ultrasonography are inconclusive or disagree. MR can provide highly accurate images, similar to those of contrast venography, in a noninvasive fashion. It is particularly useful in the iliac, femoral, popliteal, and calf muscle veins. MR venography is much less reliable in the tibial or peroneal veins.5
Chest radiography is nonspecific for thromboembolic disease, but may be used as part of the diagnostic work-up when signs and symptoms are suggestive of a PE. Ventilation-perfusion (V/Q) scanning can be used after chest radiography, with results classifying the risk of thromboembolic disease as high, moderate or low. Whilst high-rated results have shown good predictive value for PE, low- or intermediate-probability V/Q scans appear to be insufficient to make diagnosis.6,7
The D-dimer test detects thromboses via identification of the degradation products of cross‑linked fibrin. The test is usually positive in patients with thromboembolic disease; however, false-positives are possible as D-dimer levels may also be elevated in other conditions. Newer latex agglutination and rapid enzyme-linked immunosorbent D-dimer assays have very high negative predictive values for thromboembolism and seem to have overcome the shortcomings of older assays.8,9 These tests may therefore help to identify patients with suspected thromboembolic disease who require further imaging investigations.
Although assessment of biomarkers is not currently part of standard diagnostic procedures, recent evidence suggests that biomarkers of endothelial dysfunction, coagulation and tissue fibrosis may be useful in identifying individuals at risk of developing venous thromboembolic disease.10