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Pseudothrombocytopenia (PTCP) or spurious thrombocytopenia is an in-vitro sampling problem which may mislead the diagnosis towards the more critical condition of thrombocytopenia. The phenomenon may occur when the anticoagulant used while testing the blood sample causes clumping of platelets which mimics a low platelet count.[1] The phenomenon has first been reported in 1969.[2][3]
Causes
editEDTA-dependent agglutination
In some individuals, clinically insignificant antibodies may cause 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. Pseudothrombocytopenia has been reported in association with the use of EDTA as an anticoagulant, with platelet cold agglutinins, and with multiple myeloma.[citation needed] Other risk factors associated with pseudothrombocytopenia are autoimmune diseases, infections, pregnancy and the treatment with some medications such as low-molecular-weight heparin, valproic acid, insulin, antibiotics and chemotherapy medications like sunitinib.[3]
The prevalence of pseudothrombocytopenia in K2-EDTA reported in different studies ranges from 0.03 to 0.27 percent in outpatients,[3] which accounts for 15 to 30 percent of all cases of isolated thrombocytopenia. Tests can mistake small clumps of platelets for leukocytes, thus showing a pseudoleukocytosis in blood counts.[4]
Platelet satellitism
Platelet rosetting, or satelliting, around white blood cells can lead to undercounting by automated analyzers.[5]
Clotted samples
Coagulation within the sample leads to undercounting, because the analyzer samples the liquid part of the blood, while some of the platelets remain in the tube, trapped in the clot. Overfilling the sample, or inadequately mixing with anticoagulant, may allow small clots to form. Unlike platelet clumps, clots usually cannot be detected by reviewing the peripheral blood smear, but may be detected by probing with wooden sticks, including checking under the cap.[6]
Failsafes and avoiding false-positives
editA 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 sodium citrate (blue top tube) to confirm the finding of pseudothrombocytopenia may be requested if there are doubts or concerns.[7] Other alternative anticoagulants are sodium fluoride, CPT (trisodium citrate, pyridoxal 5′-phosphate and tris), CTAD (citrate, theophylline, adenosine, and dipyridamole), magnesium sulfate and acid-citrate-dextrose.[3]
References
edit- ^ "Clinical & Applied". July 1998 vol. 4 no. 3 167-169. SAGE Journals. Retrieved 12 May 2013.
- ^ Gowland E; Kay HE; Spillman JC; Williamson JR (1 July 1969). "Agglutination of platelets by a serum factor in the presence of EDTA". Journal of Clinical Pathology. 22 (4): 460–464. doi:10.1136/JCP.22.4.460. ISSN 0021-9746. PMC 474212. PMID 4978997. Wikidata Q36546397.
- ^ a b c d Benjamin Lardinois; Julien Favresse; Bernard Chatelain; Giuseppe Lippi; François Mullier (4 February 2021). "Pseudothrombocytopenia—A Review on Causes, Occurrence and Clinical Implications". Journal of Clinical Medicine. 10 (4): 594. doi:10.3390/JCM10040594. ISSN 2077-0383. PMC 7915523. PMID 33557431. Wikidata Q116885099.
- ^ Nicola Bizzaro (1 October 1995). "EDTA-dependent pseudothrombocytopenia: a clinical and epidemiological study of 112 cases, with 10-year follow-up". American Journal of Hematology. 50 (2): 104. doi:10.1002/AJH.2830500206. ISSN 0361-8609. PMID 7572988. Wikidata Q33488487.
- ^ Zandecki M, Genevieve F, Gerard J, Godon A. Spurious counts and spurious results on haematology analysers: a review. Part I: platelets. Int J Lab Hematol. 2007 Feb;29(1):4-20. doi: 10.1111/j.1365-2257.2006.00870.x. PMID: 17224004.
- ^ Zandecki M, Genevieve F, Gerard J, Godon A. Spurious counts and spurious results on haematology analysers: a review. Part I: platelets. Int J Lab Hematol. 2007 Feb;29(1):4-20. doi: 10.1111/j.1365-2257.2006.00870.x. PMID: 17224004.
- ^ Yan L, Xu S, Yang X, Luo Z, Huang C. Decision-Making Error in Platelet Transfusion Caused by EDTA-Dependent Pseudothrombocytopenia: a Case Report and Literature Review. Clin Lab. 2024 Jan 1;70(1). doi: 10.7754/Clin.Lab.2023.230703. PMID: 38213226.
Further reading
edit- W-H Choe; Y-U Cho; J-D Chae; S-H Kim (7 September 2012). "Pseudothrombocytopenia or platelet clumping as a possible cause of low platelet count in patients with viral infection: a case series from single institution focusing on hepatitis A virus infection". International Journal of Laboratory Hematology. 35 (1): 70–76. doi:10.1111/J.1751-553X.2012.01466.X. ISSN 1751-5521. PMID 22958573. Wikidata Q33403198.
- Froom, Paul; Barak, Mira (20 October 2010). "Prevalence and course of pseudothrombocytopenia in outpatients". Clinical Chemistry and Laboratory Medicine. 49 (1): 111–114. doi:10.1515/CCLM.2011.013. ISSN 1434-6621. PMID 20961195. Wikidata Q33392370.