Material and Method: One hundred cases with moderate to high probability for pulmonary embolism according to Wells criteria were prospectively collected between December 2007 and January 2010. Combined CTPA and indirect CTV were performed. Positive findings were including the visualization of filling defect within the pulmonary artery and/or deep venous system of the lower extremities. Negative findings were including no demonstrable of filling defect within pulmonary artery and deep venous system of lower extremity plus absence of clinical manifestation of pulmonary embolism and deep vein thrombosis during 3-month follow-up.

Results: One hundred cases including 31 men and 69 women with age range 16 to 95 years (mean = 61.8) were collected. Four cases were excluded according to non-opacified of the lower extremities veins. The authors found that 36 cases (38%) had pulmonary embolism, while 60 cases (62%) were negative for pulmonary embolism. For the group with positive pulmonary embolism, 11 cases (31%) did not have DVT while 25 (69%) case also had DVT as well. In the negative pulmonary embolism group, 49 (82%) did not have DVT but 11 (18%) were shown to have DVT.

Conclusion: For 96 cases with intermediate to high probability of PE, the authors needed to spend 70,909 baht more per case for the extra-investigation (combined CTPA and indirect CTV) for early detection of DVT. By comparison of two workup strategies, combined CTPA and indirect CTV of the lower extremities and CTPA with direct CTV of the lower extremities, the expense for detecting DVT in patients who also have PE will be 31,200 baht per case. Clinicians can use this value to judge between the cost effectiveness of this investigation and the expense of longer hospitalization and medical expense for late complication of DVT, which was frequently found in patients with PE. In additional, indirect CTV can increase diagnosis of deep vein thrombosis in non-PE case up to 30% in the present study.

Keywords: Combined CT pulmonary angiography (CTPA) and indirect CTV, Cost effectiveness, Pulmonary embolism