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January 17, 2007

Fixed-Dose Unfractionated Heparin vs Low-Molecular-Weight Heparin for Venous Thromboembolism

Author Affiliations

Letters Section Editor: Robert M. Golub, MD, Senior Editor.

JAMA. 2007;297(3):261-263. doi:10.1001/jama.297.3.261-b

To the Editor: In their randomized trial of acute treatment of VTE, Dr Kearon and colleagues1 concluded that fixed-dose, unmonitored, subcutaneous unfractionated heparin is as effective and safe as fixed-dose, unmonitored, subcutaneous low-molecular-weight heparin. We are concerned about this conclusion.

First, studies have shown that the risk of recurrent VTE is higher among men than women; in some studies, the risk of recurrence was almost 4 times greater in men compared with women.2,3 In Kearon et al, the unfractionated heparin group had a greater proportion of female patients than did the low-molecular-weight heparin group (173 [49%] vs 147 [42%]). The authors did not adjust for the sex difference in their statistical analysis of efficacy. Sex-related difference in the risk of recurrence has to be taken into account in the interpretation of outcome events.