ORIGINAL ARTICLE

Pseudoplatelets: a retrospective study of their incidence and interference with platelet counting

W van der Meer¹, M A MacKenzie², J W B Dinnissen¹ and M H de Keijzer¹

¹ Department of Clinical Chemistry, University Medical Centre St Radboud, 6500 HB Nijmegen, The Netherlands
² Department of Haematology, University Medical Centre St Radboud

Correspondence to:
Correspondence to:
Dr W van der Meer, Department of Clinical Chemistry (564), University Medical Centre St Radboud, PO BOX 9101, 6500 HB Nijmegen, The Netherlands;
w.vandermeer{at}akc.umcn.nl

Aims: Spurious platelet counts can be found in acute leukaemias, as a result of the fragmentation of blood cells. Microscopic examination of a blood smear should be performed to detect the presence of these so called pseudoplatelets. When present, the platelet count should be corrected because of the important clinical consequences that a lower platelet count may have in these patients.

Methods: K₃EDTA anticoagulated blood was measured on an automated blood cell counter, and a blood smear was made and stained according the May Grünwald–Giemsa method for microscopic observation. A 500 cell/particle differentiation was performed and the automated platelet count was corrected.

Results: The incidence of pseudoplatelets in 169 patients with acute leukaemia was studied. Pseudoplatelets were detected in 43 patients (25.4%), and seven patients (4.1%) were re-classified as having a major bleeding risk (platelet count, < 15 x 10⁹/litre).

Conclusions: Platelets should be determined morphologically in patients with acute leukaemia and a routine screening method for the detection of pseudoplatelets should be developed.

Keywords: pseudoplatelets; platelet counts; acute leukaemia; bleeding risk

Abbreviations: ALL, acute lymphoblastic leukaemia; AML, acute myeloid leukaemia; CBC, complete blood cell count; DIC, disseminated intravascular coagulation

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• Bain, B. J. (2005). Diagnosis from the Blood Smear. NEJM 353: 498-507 [Full Text]