Screening for venous thrombosis by ultrasonography before hospital discharge after major joint surgery

To the Editor: In a recent editorial, Gallus estimates the cost of doing ultrasonography in all patients after unilateral hip or knee replacement, with further testing in the 9% or 26% of patients, respectively, found to have deep vein thrombosis (DVT), to be about $200 000 per 1000 patients.1 We agree.

He then states, “Many would argue that extended prophylaxis is likely to be the simplest, cheapest and perhaps safest solution”.

However, prophylaxis is also expensive. Subcutaneous enoxaparin 40 mg administered daily for 30 days costs $170, or $170 000 per 1000 patients.2

In our study, we found DVTs in 1086 of 5999 patients (18.1%) before discharge,3 so that extended prophylaxis would involve 81.9% of patients receiving prophylactic doses of anticoagulants, with the risk of unwanted bleeding, despite the absence of DVT on ultrasound at Day 7 postoperatively.

In addition, if an ultrasound scan was not done before discharge, the 18.1% of patients with a DVT would receive only prophylactic (not therapeutic) doses of anticoagulant for their DVT.

We plan a further study to check the prevalence of post-discharge DVT by repeating ultrasonography at 90 days postoperatively in patients without DVT on ultrasound at Day 7. We suspect the prevalence is lower than suggested in the literature, as the data on late presentation of DVTs have been obtained by retrospective study of the number of patients re-admitted to hospital with DVT.

Finally, on the question of whether performing ultrasonography on all patients has clinical benefit, we concur with Gallus when he writes that “Logic suggests it should . . .”.