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Pseudothrombocytopenia or spurious thrombocytopenia is an in-vitro sampling problem which may mislead the diagnosis towards the more critical condition of thrombocytopenia. The phenomenon occurs when the anticoagulant used while testing the blood sample causes clumping of platelets which mimics a low platelet count. ^[1]

Causes

It is a relatively uncommon phenomenon caused by in vitro agglutination of platelets. As a result of platelet clumping, platelet counts reported by automated counters may be much lower than the actual count in the blood because these devices cannot differentiate platelet clumps from individual cells. The incidence of pseudothrombocytopenia reported in different studies ranges from 0.09 to 0.21 percent, which accounts for 15 to 30 percent of all cases of isolated thrombocytopenia. Pseudothrombocytopenia has been reported in association with the use of EDTA as an anticoagulant, with platelet cold agglutinins, and with multiple myeloma.

Failsafes and avoiding false-positives

A pseudothrombocytopenia false-positive result may occur when automated platelet counting devices are used. As a means of double checking the results, the patient's blood sample is often examined under a microscope. If the clumping is visible and the number of platelets appears normal, pseudothrombocytopenia may be concluded. A second sample run with a different anticoagulant such as citrate (blue top tube) to confirm the finding of pseudothrombocytopenia may be requested if there are doubts or concerns.

References

^ "Clinical & Applied". July 1998 vol. 4 no. 3 167-169. SAGE Journals. Retrieved 12 May 2013.

UpToDate Contents

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English Journal

Thrombocytopenia Pitfalls: Misdiagnosing Type 2B von Willebrand Disease as Ethylenediaminetetraacetic Acid-Dependent Pseudothrombocytopenia.

Kumar R1, Creary S1, Varga EA2, Kahwash SB3.
The Journal of pediatrics.J Pediatr.2016 May 20. pii: S0022-3476(16)30187-1. doi: 10.1016/j.jpeds.2016.04.077. [Epub ahead of print]
PMID 27215777

A case report of sudden thrombocytopenia detected only by in vitro analysis.

Noguchi S1, Kitayama M2, Niwa H3, Tamai Y4, Hirota K3.
Journal of anesthesia.J Anesth.2016 May 3. [Epub ahead of print]
We experienced an unexpected thrombocytopenia detected only in vitro during radical prostatectomy for a 66-year-old patient. Thrombocytopenia with platelet aggregation was observed in a blood sample obtained using a heparinized syringe (not by ethylene diamine tetra-acetic acid tube). Although we co
PMID 27142615

Platelet Function Tests in Bleeding Disorders.

Lassila R1.
Seminars in thrombosis and hemostasis.Semin Thromb Hemost.2016 Apr;42(3):185-90. doi: 10.1055/s-0036-1571307. Epub 2016 Feb 17.
Functional disorders of platelets can involve any aspect of platelet physiology, with many different effects or outcomes. These include platelet numbers (thrombocytosis or thrombocytopenia); changes in platelet production or destruction, or capture to the liver (Ashwell receptor); altered adhesion t
PMID 26886396

Japanese Journal

新生児期に一過性に発症したEDTA依存性偽性血小板減少症

大野令央義,小林正夫,山本弥寿子,工藤美樹
日本産婦人科・新生児血液学会誌 = The Japanese journal of obstetrical, gynecological & neonatal hematology 20(1), "S-113"-"S-114", 2010-06-01
NAID 10026710628