Antithrombotic treatment in a patient with thrombocytopenia

Can antithrombotic treatment be used in a patient with thrombocytopenia? If yes, what are the indications?

Mark Crowther, MD: That is a great question. There is actually relatively little data to answer. Despite the frequency with which patients with low platelet counts are [treated with antithrombotics], questions come up about the use of antithrombotics.

There is some data that have come out of a group in New York City led by Gerald Soff that has looked at this issue of thresholds for platelet counts. I think that the summary would be that if the platelet count is >50 × 10⁹/L, most of us would be comfortable anticoagulating the patient using usual therapeutic doses. Obviously, you would temper that if they had bleeding or other complications. If the platelet count is <50 × 10⁹/L but it is due to a condition which is associated with an enhanced risk of thrombosis, like heparin-induced thrombocytopenia, most of us would be comfortable anticoagulating that patient irrespective of the platelet count; even if it is 12 × 10⁹/L, we would anticoagulate that patient.

If the platelet count is low because of chemotherapy, which would be the most common circumstance, I think most people would be comfortable with therapeutic anticoagulants to a platelet count >50 × 10⁹/L. Somewhere between 50 and 30 × 10⁹/L most people would get a little bit uncomfortable and perhaps consider dose reduction. Probably <30 × 10⁹/L to maybe 15 × 10⁹/L or maybe 20 × 10⁹/L many of us would be comfortable with prophylactic-dose anticoagulation, and <15 or <20 × 10⁹/L most people would probably be uncomfortable with anticoagulants. In those circumstances you would have to think about alternate therapies based on the reason the patient is on anticoagulants. For example, if they have atrial fibrillation, most of us would just stop anticoagulants and wait until the platelet count recovers.