Term	Definition
Anticoagulants	A drug or other substance that prevents or slows down the process of blood forming a clot (a solid mass (Cambridge 2024))
Arterial	Related to or flowing in an artery (Cambridge 2024)
Autoimmune heparin‐induced thrombocytopenia (aHIT)	Refers to a condition in which antiplatelet factor‐4 (PF4) antibodies activate platelets even in the absence of heparin (heparin‐independent platelet activation (Greinacher 2017))
COVID‐19	An infectious disease caused by a coronavirus (Cambridge 2024)
Deep vein thrombosis (DVT)	Occurs when a blood clot forms in a deep vein, usually in the lower leg, thigh, or pelvis. DVTs can also occur in the arms, especially if there is a large intravenous central line in the vein (NIH 2024).
Heparin (also known as unfractionated heparin (UFH))	A fast‐acting blood thinner that works together with antithrombin, a natural protein in the body, to block clot formation. Specifically, UFH binds to antithrombin and enhances its ability to inhibit two of the body’s most potent clotting factors – factor Xa and factor IIa – usually within minutes. As with all forms of heparin, UFH does not break down clots, but keeps them from growing and stops new ones from forming. This allows the body the time necessary to dissolve existing blood clots gradually. UFH is administered in the hospital via an intravenous (IV) catheter inserted into an arm vein or as a subcutaneous injection under the skin. The initial dosage is determined by body weight. If you are administered IV UFH, you can expect frequent blood monitoring – even several blood tests daily – to ensure proper dosing, as blood levels of the medication can change periodically (NBCA 2024a).
Heparin‐induced thrombocytopenia (HIT)	A life and limb‐threatening prothrombotic, immune‐mediated complication that occurs with an incidence of up to 5% following administration of UFH for a variety of prophylactic or therapeutic applications (Greinacher 2006)
Low molecular weight heparin (LMWH)	Derived from UFH by digestion or depolymerisation of longer chains of heparin into shorter chains by chemical or enzymatic means. These short strands make LMWH last longer and act more predictably in the body than UFH. Although LMWH and UFH work similarly to inhibit clotting factors, LMWH can be self‐administered at home via subcutaneous injection and does not require regular blood monitoring, which is necessary for UFH treatment. As with all heparins, LMWH dosing is based on a person’s weight (NBCA 2024)
Placebo	A fake (or dummy) treatment given to participants in the control group of a clinical trial. It is indistinguishable from the actual treatment that is given to participants in the experimental group. The aim is to determine what effect the experimental treatment had ‐ over and above any placebo effect caused because someone had (or thinks they had) care or attention (NICE 2024).
Platelet	A very small cell in the blood that makes it thicker and more solid in order to stop bleeding caused by an injury (Cambridge 2024)
Pulmonary embolism (PE)	Occurs when a clot breaks loose and travels through the bloodstream to the lungs (NIH 2024)
Quasi‐randomised controlled trial (quasi‐RCT)	A study in which participants are divided by date of birth or by hospital register number, i.e. not truly randomly divided into separate groups, to compare different treatments
Randomised controlled trial (RCT)	A study in which a number of similar people are randomly assigned to 2 (or more) groups to test a specific drug, treatment, or other intervention. One group (the experimental group) receives the intervention being tested, the other (the comparison or control group) receives an alternative intervention, a dummy intervention (placebo), or no intervention at all. The groups are followed to see how effective the experimental intervention was. Outcomes are measured at specific times and any difference in response between the groups is assessed statistically. This method is also used to reduce bias (NICE 2024)
SARS‐CoV‐2	A form of coronavirus that causes a serious infectious illness with difficulty in breathing and sometimes death, and has been responsible for many cases of illness since 2019. SARS‐CoV‐2 is an abbreviation for Severe Acute Respiratory Syndrome Coronavirus 2 (Cambridge 2024)
Thrombosis	A medical condition in which the flow of blood in the body is blocked by a clot of blood (Cambridge 2024)
Vaccine‐induced thrombocytopenia and thrombosis (VITT)	A vaccine adverse event; an immune‐mediated disease that can lead to thromboembolic complications, platelet activation, and thrombocytopenia (Oldenburg 2021)
Vascular	Relating to the vessels (Cambridge 2024)
Venous	Of or relating to the veins (Cambridge 2024; OED 2024)
Venous thromboembolism (VTE)	Venous thromboembolism (VTE) is a condition that occurs when a blood clot forms in a vein. VTE includes deep vein thrombosis (DVT) and pulmonary embolism (PE (NIH 2024))