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Transfusion medicine

Therapeutic apheresis

Plateletpheresis


Brian D. Adkins, M.D.
Garrett S. Booth, M.D., M.S.

Last author update: 14 March 2024
Last staff update: 14 March 2024

Copyright: 2002-2024, PathologyOutlines.com, Inc.

PubMed Search: Plateletpheresis

Brian D. Adkins, M.D.
Garrett S. Booth, M.D., M.S.
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Table of Contents
Definition / general | Essential features | Terminology | Pathophysiology | Clinical features | Symptoms | Vascular access | Indications | Volume exchanged & technical details | Adverse events | Laboratory | Case reports | Treatment | Peripheral smear images | Sample assessment & plan | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2
Cite this page: Adkins BD, Booth GS. Plateletpheresis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/transfusionmedplateletpheresis.html. Accessed April 19th, 2024.
Definition / general
  • Thrombocytapheresis (or plateletpheresis) is the removal of platelet cells via apheresis
Essential features
  • Therapeutic thrombocytapheresis is performed to acutely lower a patient's platelet (PLT) count due to symptoms associated with thrombocytosis, such as hemorrhagic or thromboembolic complications
Terminology
  • Thrombocytosis (J Clin Apher 2023;38:77, Blood 2014;124:1997)
    • Usually defined as a platelet count > 450,000 - 500,000/µL
    • Can be caused by an underlying hematologic malignancy (primary thrombocytosis) or by a reactive process (secondary thrombocytosis) (Leuk Res 2017;58:14)
    • Primary thrombocytosis
    • Secondary thrombocytosis
      • More common, accounting for 80 - 90% of cases (Intern Med 2022;61:3323)
      • Platelet function is relatively normal
      • Carries significantly smaller risk of hemorrhage or thrombosis
Pathophysiology
  • Thrombosis can occur as a result of congestion and increased viscosity secondary to high platelet counts
  • This tends to be more common in clonal thrombocytosis unless patients have underlying predisposition to clot formation (N Engl J Med 2004;350:1211)
  • Likewise, bleeding tends to occur as a result of qualitative platelet defects seen in myeloproliferative disorders (N Engl J Med 2004;350:1211)
    • Extremely high platelet counts tend to associate with an acquired von Willebrand syndrome with clearance of high molecular weight von Willebrand factor (vWF) and bleeding (Haematologica 2002;87:264)
Clinical features
Symptoms
  • Patients may present with platelet type bleeding at mucous membranes or gastrointestinal tract, digital ischemia or massive thromboembolic events such as pulmonary embolism or hepatic vein thrombosis (N Engl J Med 2004;350:1211)
  • Platelet count does not predict symptoms (J Clin Apher 2023;38:77)
Vascular access
Indications
  • The only indications for thrombocytapheresis according to the American Society for Apheresis (ASFA) are symptomatic and prophylactic or secondary thrombocytosis (J Clin Apher 2023;38:77)
    • Symptomatic thrombocytosis - ASFA category II
      • Bring platelet count to < 350 - 450 x 109/L in patients with an acute thrombohemorrhagic event
    • Prophylaxis - ASFA category III
      • Pregnant patients, surgical patients, etc.
      • < 450 - 600 x 109/L may be an appropriate count for prophylaxis per ASFA
Volume exchanged & technical details
  • 1 procedure or until resolution of symptoms
  • 1.5 - 2 blood volumes
  • This usually reduces the platelet count by 30 - 60%
    • Patients with spleens will recover counts more quickly than asplenic patients due to splenic platelet content (Leuk Res 2017;58:14)
Adverse events
  • This is an apheresis procedure, with its typical complications
  • Also complications from the underlying myeloproliferative neoplasm, hypotension, citrate related toxicity, bleeding and infection
Laboratory
  • Elevated platelet count
  • Reduced vWF and factor VIII levels
Case reports
  • 24 year old woman with essential thrombocythemia was treated prophylactically with thrombocytapheresis (Case Rep Oncol 2020;13:675)
  • 25 year old man with triple negative essential thrombocythemia presented with thrombosis and acquired von Willebrand syndrome and was treated with thrombocytapheresis (Am J Case Rep 2020;21:e924560)
  • 51 year old woman with essential thrombocythemia was treated for postoperative bleeding with 2 thrombocytapheresis procedures (Transfusion 2021;61:3277)
Treatment
  • Treatment of underlying condition should be initiated for primary thrombocytosis with cytoreductive agents (hydroxyurea) (J Clin Apher 2023;38:77)
    • Interferon alpha should be used in pregnancy
    • In symptomatic or prophylactic thrombocytapheresis, the platelet goal should be < 450 x 109/L
Peripheral smear images

Images hosted on other servers:
Thrombocytosis seen in CML

Thrombocytosis seen in CML

Sample assessment & plan
  • Assessment: A 63 year old man with JAK2+ myeloproliferative neoplasm underwent thrombocytapheresis due to acute thromboembolism.
  • Plan: 1.5 blood volumes were processed. If counts remain high or patient experiences symptoms related to thrombocytosis, further intervention may be considered.
Board review style question #1
A patient presents with essential thrombocythemia and has ongoing mucocutaneous and gastrointestinal bleeding. A platelet count is found to be > 2,000 x 109. Unfortunately, 2 days later the patient remains symptomatic. What is the goal platelet count?

  1. < 10 - 20 x 109/L
  2. < 350 - 450 x 109/L
  3. < 750 - 1,000 x 109/L
  4. < 1,500 - 1,750 x 109/L
Board review style answer #1
B. < 350 - 450 x 109/L. ASFA guidelines recommend a count of 350 - 450 x 109/L for symptomatic thrombocytosis. The remaining answers fall outside of ASFA recommendations. Answer A is incorrect because it is too low and could lead to bleeding complications, requiring platelet transfusion. Answers C and D are incorrect because < 750 - 1,000 x 109/L and < 1,500 - 1,750 x 109/L are both still too high and could potentially contribute to depletion of von Willebrand factor, furthering the symptomatic thrombocytosis associated bleeds.

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Reference: Plateletpheresis
Board review style question #2
Why do asplenic patients with thrombocytosis recover their platelet counts more slowly than patients with spleens after thrombocytapheresis?

  1. Absence of extramedullary hematopoiesis
  2. Asplenia impacts fluid balance leading to thrombocytopenia
  3. Lack of splenic macrophages
  4. Spleen helps maintain platelet count with sequestered platelets
Board review style answer #2
D. Spleen helps maintain platelet count with sequestered platelets. The spleen contains ~25 - 30% of the body's platelets and some of these will peripheralize after thrombocytapheresis or in times of stress in patients with a spleen (Leuk Res 2017;58:14). Asplenic patients do not have this residual pool of platelets (StatPearls: Physiology, Spleen [Accessed 31 January 2024]). Answer A is incorrect because extramedullary hematopoiesis occurs mainly in very young patients or those with a bone marrow filling lesion, such as a hematologic malignancy, metastasis or marrow fibrosis; nevertheless, it does not act as a platelet reserve but rather a producer of platelets. Answer B is incorrect because fluid balance is maintained predominantly by the kidneys as opposed to the spleen. Answer C is incorrect because splenic macrophages help clear aging platelets and red cells and do not release or store platelets.

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Reference: Plateletpheresis
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