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In the original study on isolated thrombocytopenia in childhood,(1) pseudothrombocytopenia was not included. Two cases of pseudothrombocytopenia were detailed in a prior publication.(2) That said, Sriwijitalai and Wiwanitkit’s comments(3) are important, as they are about pre-analytical, technical issues rather than genuine pathology. Although the mechanism is not fully understood, the occurrence of pseudothrombocytopenia is most likely a multifactorial phenomenon in which pre-existing autoantibodies are allowed to agglutinate platelets in vitro during sample storage, in a time-, temperature-, anticoagulant- and disease-dependent process.(4) However, the condition can be readily identified by examination of the blood film (
We recently encountered a four-month-old boy whose automated full blood count showed isolated thrombocytopenia of 17 × 109/L with no clinical signs of bleeding. Examination of the blood film revealed a striking absence of normal platelets on the whole film, while the remaining platelets appeared degranulated and scattered in small clumps (
Photomicrographs of peripheral blood films show (a) typical platelet clumping (black arrow) in a case of pseudothrombocytopenia, probably due to exposure to ethylenediaminetetraacetic acid anticoagulant during storage; and (b) degranulated platelets (white arrows) with some appearing as small clumps (circled) in a four-month-old child (Wright’s, × 100).
Keeping up laboratory quality can be challenging, but the importance of a carefully examined peripheral blood film cannot be overemphasised, whether the thrombocytopenia is spurious or genuine.
1. Lee AC. Isolated thrombocytopenia in childhood: what if it is not immune thrombocytopenia? Singapore Med J 2018; 59:390-3.
2. Lee AC. Haematologist-reviewed peripheral blood smear in paediatric practice. Singapore Med J 2018; 59:64-8.
3. Sriwijitalai W, Wiwanitkit V. Comment on: Isolated thrombocytopenia in childhood: what if it is not immune thrombocytopenia? Singapore Med J 2018; 59:508.
4. Zhang L, Xu J, Gao L, Pan S. Spurious thrombocytopenia in automated platelet count. Lab Med 2018; 49:130-3.