Pseudothrombocytopenia: a laboratory artifact with potentially serious consequences

Area of Science:

• Hematology
• Clinical Pathology
• Laboratory Medicine

Background:

• Unexpected low platelet counts (thrombocytopenia) may indicate pseudothrombocytopenia.
• Pseudothrombocytopenia is an artifactual reduction in platelet count due to platelet clumping.
• It is crucial to differentiate true thrombocytopenia from pseudothrombocytopenia to ensure accurate diagnosis and treatment.

Purpose of the Study:

• To outline methods for suspecting and confirming pseudothrombocytopenia.
• To provide guidance on laboratory techniques for accurate platelet counting.
• To highlight the role of automated hematology analyzers in detecting EDTA-induced platelet clumping.

Main Methods:

• Examination of peripheral blood smears for platelet morphology and clumping.
• Repeating platelet counts using alternative anticoagulants (e.g., sodium citrate) or collection methods (e.g., finger-stick with phase microscopy).
• Analyzing histogram displays (Coulter) or X-Y scatter plots (Technicon H6000) from automated hematology analyzers.

Main Results:

• EDTA (ethylenediaminetetraacetic acid) is a common cause of in vitro platelet clumping, leading to spuriously low platelet counts.
• Blood smear examination can reveal EDTA-induced platelet aggregation.
• Automated analyzers with specific display features can alert operators to potential pseudothrombocytopenia.

Conclusions:

• Pseudothrombocytopenia should be considered in cases of unexpected low platelet counts without bleeding symptoms.
• A combination of smear review, repeat counting with different anticoagulants, and analyzer data interpretation is essential for accurate diagnosis.
• Proper laboratory techniques prevent misdiagnosis and inappropriate patient management.