The OAT Trail: The Obesity Anti-Coagulation Thromboprophylaxis Trial. (NCT07559643) | Clinical Trial Compass
Not Yet RecruitingNot Applicable
The OAT Trail: The Obesity Anti-Coagulation Thromboprophylaxis Trial.
Ireland180 participantsStarted 2026-08-01
Plain-language summary
Blood clots in the legs or lungs (called venous thromboembolism or VTE) are one of the most serious complications after weight loss surgery. Most blood clots occur after patients go home from hospital, within the first 30 days after surgery. To prevent blood clots, all patients having weight loss surgery receive a daily blood-thinning injection for 21 days after their operation.
Two blood-thinning injections are currently used at St Vincent's University Hospital for this purpose: enoxaparin (Clexane®) and tinzaparin (Innohep®). Both belong to a group of medicines called low molecular weight heparins (LMWHs). Patients with obesity process these medicines differently to the general population, and previous studies from our hospital have shown that fewer than 53% of patients achieve adequate blood-thinning levels with either injection when measured by a blood test called an anti-Xa level.
Patients will be randomly assigned (like a coin toss) to receive either tinzaparin or enoxaparin for 21 days after their surgery. Both injections are already in routine use at this hospital. A single extra blood sample will be taken on the second day after surgery to measure the anti-Xa level, which tells us whether the injection is providing adequate protection against blood clots. This blood sample will be taken at the same time as routine post-operative blood tests so that no additional blood draws are required.
The study will also look at rates of blood clots and bleeding events within 30 days of surgery, and will ask patients to complete a short questionnaire at their six-week follow-up appointment about their experience with the injection.
Who can participate
Age range
18 Years
Sex
ALL
See this in plain English?
AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.
Inclusion Criteria:
* Age ≥18 years
* BMI ≥40 kg/m², or BMI ≥35 kg/m² with at least one obesity-related comorbidity (type 2 diabetes, hypertension, obstructive sleep apnoea, dyslipidaemia, or metabolic dysfunction-associated steatotic liver disease (MASLD))
* Scheduled to undergo laparoscopic bariatric surgery (sleeve gastrectomy or gastric bypass) at St Vincent's University Hospital, Dublin, Ireland
* Capacity to provide written informed consent
Exclusion Criteria:
* Current therapeutic anticoagulation for any indication Known allergy or hypersensitivity to tinzaparin, enoxaparin, heparin, or any heparin-derived product, including documented heparin-induced thrombocytopaenia (HIT) Any other contraindication to LMWH therapy Severe renal impairment (eGFR \<30 mL/min/1.73m²) Known haematological disorder or coagulopathy Pregnancy, breastfeeding, or planning pregnancy during the study period Active major bleeding or high bleeding risk at the discretion of the treating clinician Inability to provide written informed consent Participation in another interventional clinical study within 30 days prior to enrolment
Questions worth asking your doctor
Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.
1Based on my diagnosis and history, is this trial worth exploring for me — or is there a standard treatment we should try first?
2What does this trial's phase tell us about how much is already known about its safety and benefit?
3What would taking part actually involve for me — visits, tests, time, and travel?
4What are the known and possible risks or side effects I should weigh, and how would they be monitored?
5If this trial isn't the right fit, what other options or trials would you suggest I look into?
Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.
Questions for the trial coordinator
The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.
1What does taking part actually involve week to week — how many visits, where, and how long does each one take?
2What costs are covered by the study, and what might I have to pay for myself, including travel, parking, or time off work?
3What happens during screening, and what happens if the study team confirms I don't meet the criteria after those tests?
4Who pays for the scans, blood work, and other tests the trial requires — the study, my insurance, or me?
5How will being in the trial affect my regular care, and will my own doctor stay informed and involved?
6Can I leave the trial at any point if I change my mind, and what would happen to my care if I do?
A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.
What they're measuring
1
Proportion of participants achieving prophylactic anti-Xa levels
Timeframe: Post-operative day 2 (4 hours after third LMWH dose)