Pascale Faisse, Hervé Guenneguez, Henri Bounameaux, Christine Jurus, Susan R. Kahn, D. Brisot, Jean-Philippe Galanaud, Clarisse Choquenet, Claudine Hamel-Desnos, M.-T. Barrellier, Marc Philip Righini, Marc Carrier, Olivier Pichot, Jean-Pierre Laroche, Arnaud Perrier, Helia Robert-Ebadi, Lucia Mazzolai, Myriam Martin, Sandrine Accassat, Antoine Diard, Bernadette Mermilllod, Grégoire Le Gal, Isabelle Quéré, Service d'angiologie et d'hémostase (MR), Hôpital Universitaire de Genève, Centre Hospitalier Régional Universitaire [Montpellier] (CHRU Montpellier), Service des Explorations Fonctionnelles [CHU Caen], CHU Caen, Normandie Université (NU)-Tumorothèque de Caen Basse-Normandie (TCBN)-Normandie Université (NU)-Tumorothèque de Caen Basse-Normandie (TCBN), Hôpital Privé Saint Martin de Caen, Clinique du Tonkin, Clinique de Médecine Vasculaire, Université Joseph Fourier - Grenoble 1 (UJF)-CHU Grenoble, Université Jean Monnet [Saint-Étienne] (UJM), Department of Medicine (Dep Med - OTTAWA), Ottawa Hospital Research Institute [Ottawa] (OHRI), Groupe d'Etude de la Thrombose de Bretagne Occidentale (GETBO), Université de Brest (UBO)-Institut Brestois Santé Agro Matière (IBSAM), Université de Brest (UBO)-Université de Brest (UBO), CIC Brest, Université de Brest (UBO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Hôpital de la Cavale Blanche, Cabinet (JPL), Cabinet JP Laroche et G Muller, Department of Internal Medicine (AP), Geneva University Hospital (HUG), Département de Médécine Vasculaire [CHU Caen], Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-CHU Caen, Normandie Université (NU)-Tumorothèque de Caen Basse-Normandie (TCBN)-Tumorothèque de Caen Basse-Normandie (TCBN), Hôpital Privé Saint Martin Caen, Centre Hospitalier Annecy-Genevois [Saint-Julien-en-Genevois], and CHU Saint-Etienne
International audience; BACKGROUND:The efficacy and safety of anticoagulant treatment is not established for patients with acute symptomatic deep vein thrombosis (DVT) of the calf. We aimed to assess whether therapeutic anticoagulation is superior to placebo in patients with symptomatic calf DVT.METHODS:In this randomised, double-blind, placebo-controlled trial, we enrolled low-risk outpatients (without active cancer or previous venous thromboembolic disease) with a first acute symptomatic DVT in the calf from 23 university medical centres or community medical clinics in Canada, France, and Switzerland. We randomly assigned (1:1) patients to receive either the low-molecular-weight heparin nadroparin (171 UI/kg, subcutaneously, once a day) or placebo (saline 0·9%, subcutaneously, once a day) for 6 weeks (42 days). Central randomisation was done using a computer-generated randomisation list, stratified by study centre. Random allocation sequences of variable block size were centrally determined by an independent research clinical centre. Study staff, patients, and outcome assessors (central adjudication committee) were masked to group assignment. Numbered boxes of active drug or placebo were provided to pharmacies in identical packaging. All patients were prescribed compression stockings and followed up for 90 days. The primary efficacy outcome was a composite measure of extension of calf DVT to proximal veins, contralateral proximal DVT, and symptomatic pulmonary embolism at day 42 in the modified intention-to-treat population. The primary safety outcome was major or clinically relevant non-major bleeding at day 42. The trial was registered with ClinicalTrials.gov, number NCT00421538.FINDINGS:Between Feb 1, 2008, and Nov 30, 2014, we screened 746 patients, enrolling 259 patients (50% of the prespecified sample size), before the trial steering committee terminated the trial because of expiry of study drug and slow recruitment. The intention-to-treat analysis population comprised 122 patients in the nadroparin group and 130 in the placebo group. There was no significant difference between the groups in the composite primary outcome, which occurred in four patients (3%) in the nadroparin group and in seven (5%) in the placebo group (risk difference -2·1%, 95% CI -7·8 to 3·5; p=0·54). Bleeding occurred in five patients (4%) in the nadroparin group and no patients in the placebo group (risk difference 4·1, 95% CI 0·4 to 9·2; p=0·0255). In the nadroparin group one patient died from metastatic pancreatic cancer and one patient was diagnosed with heparin-induced thrombocytopenia type 2.INTERPRETATION:Nadroparin was not superior to placebo in reducing the risk of proximal extension or venous thromboembolic events in low-risk outpatients with symptomatic calf DVT, but did increase the risk of bleeding. Avoidance of systematic anticoagulation for calf DVT could have a substantial impact on individual patients and from a public health perspective.FUNDING:Swiss National Science Foundation, the Programme Hospitalier de Recherche Clinique in France, and the Canadian Institutes of Health Research.