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

In reply: O’Reilly and colleagues belatedly address the need to consider bleeding risk and costs when choosing between management routines designed to prevent venous thrombosis and pulmonary embolism. Their otherwise valuable article1 failed to record bleeding rates when patients (almost 17%) with subclinical calf-vein thrombosis were exposed to therapeutic (not prophylactic) anticoagulant dosages. Nor did they evaluate the dollar and manpower costs of their complex management routines.

Present evidence-based international guidelines from the Seventh ACCP (American College of Chest Physicians) Conference on Antithrombotic and Thrombolytic Therapy recommend effective prophylaxis for at least 10 days in all patients having hip or knee replacement, extending to 28–35 days after hip replacement.2 The ACCP guidelines also recommend against routine use of ultrasound screening because it is “neither clinically effective nor cost effective”.2 This is a Grade 1A recommendation from the ACCP (“Grade 1” implies certainty “that the benefits do, or do not, outweigh the risks, burdens, and costs”; “Grade A” refers to recommendations based on “randomized clinical trials with consistent results [that] provide evidence with a low likelihood of bias”).3 To reverse this recommendation would require randomised comparisons between routine prophylaxis alone or routine prophylaxis supplemented by screening ultrasonography — powered to permit meaningful measures, in both groups, of thromboembolism rates, bleeding rates and costs. Routinely screening for subclinical thrombosis after major joint surgery should not be done outside suitably designed clinical trials until such evidence is available. The role of logic in medicine is to generate hypotheses, which must then be tested by clinical trial. Unfortunately, evidence derived from uncontrolled cohort studies remains limited to Grade C (based on “observational studies or [on] generalization from one group of patients included in randomized trials to a different, but somewhat similar, group of patients”).3