Pseudothrombocytopenia is a false positive for low platelets caused by an in vitro problem with blood collection. It can be distinguished from true thrombocytopenia by examining the blood under a microscope and using a different anticoagulant. Follow-up testing may be necessary for patients with symptoms of thrombocytopenia.
Pseudothrombocytopenia is the appearance of low platelets in a blood test that is caused by an in vitro problem with blood collection, rather than a disorder in the patient. Clinically, it can cause concern and confusion because there may be concerns about the patient’s health, but there are some steps that can be taken when thrombocytopenia is suspected to distinguish between a true case and a false positive. It is important to evaluate patients carefully to avoid potentially expensive and invasive tests such as bone marrow biopsy to check platelet function.
In some cases, when blood is processed with a chemical called ethylenediaminetetraacetic acid (EDTA) as an anticoagulant, it causes platelets to clog. Automated platelet counting equipment will signal that the count is low, indicative of thrombocytopenia, in which the patient’s blood does not have enough platelets. This is a potential concern, as it could put the patient at risk for excessive bleeding and complications such as bruising, joint damage, and related problems.
If the blood is examined under a microscope, the clumping will be visible and the platelet count will appear normal. This suggests pseudothrombocytopenia, which means that the patient’s platelet count is perfectly fine and the problem lies with the anticoagulant used. In case of doubts or concerns, a second analysis of the sample with a different anticoagulant may be requested to confirm the result. Repeated samples should show a normal platelet count, indicating that the patient’s blood chemistry is healthy, at least in this respect.
Routine blood tests are common for evaluating patients with suspected medical disorders, and false positives such as pseudothrombocytopenia occasionally occur. Laboratories use a variety of safety devices to avoid them and have measures in place to deal with positive results when they arise so they can be confirmed with a minimum of patient disruption. In a situation where lab results indicate thrombocytopenia but the patient does not have symptoms such as fatigue and excessive bleeding, the doctor may consider pseudothrombocytopenia. Technicians can check your blood under a microscope to count platelets, and a second blood test can be done if necessary.
Patients who have symptoms suggestive of thrombocytopenia may need follow-up testing with a different blood thinner to confirm positive results. If the second test indicates that the platelet count is indeed low, further tests to explore the cause may be recommended. This can help the doctor develop treatment recommendations to stabilize the patient’s platelets and prevent complications.
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