A systematic review on anti-Xa monitoring in the therapeutic use of low-molecular-weight heparins

Low-molecular-weight heparins are widely utilized, including in special patient populations (eg, patients with renal impairment, pregnancy, and obesity). Monitoring with anti-Xa measurements is often used, but the effectiveness of anti-Xa—based dose adjustments remains uncertain. This systematic review aimed to provide an informed assessment of the usefulness of anti-Xa monitoring and subsequent dose adjustments in these patients. The primary outcome was the incidence of clinical events, such as major bleeding and venous thromboembolism, compared between patients with and without anti-Xa monitoring. Secondary outcomes were the correlation between anti-Xa levels and bleeding or thromboembolic complications and the frequency of dose adjustments based on anti-Xa levels. A total of 48 studies, both randomized controlled trials and observational studies, were included. All studies had a high risk of bias. Five studies indicated comparable rates of bleeding and thromboembolic complications in anti-Xa–monitored and unmonitored patients. Measurement of anti-Xa levels was associated with frequent dose adjustments. The correlation between anti-Xa levels and both bleeding and thromboembolic complications was weak, if it was present at all. Overall, this review highlights the limited evidence supporting the use of anti-Xa monitoring for dose adjustments in the therapeutic use of low-molecular-weight heparins. Therefore, we conclude that measuring anti-Xa levels is currently not justified. Only new, high-quality, preferably randomized studies could indicate otherwise.