Dr Robert Bird, member of our Medical Advisory Board, has shared information about ITP patients being at an increased risk of blood clots and not just bleeding.
The main worry for most people with ITP, and for doctors treating ITP, is bleeding. Therefore, it may come as a surprise that ITP is also associated with an increased risk of blood clotting, particularly deep vein thrombosis (DVT). Data from the UK ITP registry indicates that people with ITP have a risk ratio of 1.2 (20% increased risk) for developing clots compared to people of similar age without ITP. Another surprise is that blood clots can occur at any platelet count and a low platelet count is not protective.
The increased risk of blood clots is due to the antibodies which cause ITP “activating” platelets (making them more sticky).
Safe platelet count for treatment of clots
The treatment of more serious clots involves “blood thinning” medication or anticoagulation. This can be challenging when the platelet count is very low but is generally regarded as safe if the platelet count is over 50. Platelets in ITP usually work very well, compared to platelets in patients with other causes of thrombocytopenia, such as chemotherapy or myelodysplasia. For this reason, particularly in the setting of an acute (very recent) thrombosis, most ITP specialists are happy to use anticoagulation with a platelet count greater than 30.
DVT in the leg
Most blood clots occur in the legs, with pain, redness and swelling of the leg being the symptoms of leg DVT. People with a clot in the leg often feel is if they had torn a calf muscle but can’t remember a specific injury.
One particular situation common to ITP in which blood clots are seen is immediately following splenectomy. In this case, the clots are usually in the deep veins close to where the spleen was located. These include the portal vein. If ITP patients with recent splenectomy are scanned to look for clots in these veins, they are found in more than 50% cases. However, not all clots cause symptoms.
Thrombopoietin receptor agonists (TPORAs)
Treating ITP patients with blood clots has become easier over the past 10 years, particularly those who have had a splenectomy, as the TPORAs (Romiplostim and Eltrombopag) usually enable a safe and stable platelet count to be maintained, so that using blood thinners (anticoagulants) present no more risk than they would to someone without ITP. Sometimes if a large blood clot has caused complications in a person who still has a spleen, this can make splenectomy itself very risky, so that person may become eligible for Romiplostim or Eltrombopag on the PBS. It is known that neither Romiplostim nor Eltrombopag cause platelet activation.
In order that the risk of blood clots is minimised for people with ITP, it is important that everyone with a safe and stable platelet count who has risk factors is treated in the same way as those without ITP. This would include the use of drugs such as aspirin or clopidogrel (antiplatelet drugs) for those with previous heart attacks or strokes, blood thinners such as Warfarin, Rivaroxaban, Apixaban or Dabigatran for those with atrial fibrillation (AF). Routine blood thinning injections or tablets should also be used in people with ITP undergoing surgery, provided the platelet count is at a safe level (see above).
There are also things that people with ITP can do to reduce risks. People with a safe platelet count should discuss whether blood thinning injections or tablets should be used if a long haul flight is planned. During the flight, it is best to stay hydrated, by drinking plenty of water, doing leg exercises (as shown in the airline in flight magazine) or walking around the cabin and possibly wearing properly fitted compression stockings.