Artefactually-normal automated platelet counts due to malaria-infected RBC

Area of Science:

• Hematology
• Clinical Pathology
• Parasitology

Background:

• Automated blood analyzers utilize impedance and optical technologies for platelet counting.
• Protein aggregates, cellular fragments, and other particles can interfere with these automated counts, leading to inaccurate platelet values.
• Pseudo-thrombocytopenia or falsely elevated platelet counts can occur due to such interferences.

Observation:

• A case of treated malaria presented with a normal platelet count on automated analysis.
• Examination of the blood smear revealed small red blood cells infected with Plasmodium falciparum trophozoites.
• These infected red blood cells interfered with the platelet count in the Cell Dyn 4000 analyzer.

Findings:

• The Cell Dyn 4000 exhibited distinct interference patterns in both its impedance and optical platelet counts due to infected red blood cells.
• The automated analysis initially suggested thrombocytopenia (low platelet count).
• Confirmation of thrombocytopenia was achieved through a phase-contrast microscopic platelet count, a more reliable method in this context.

Implications:

• This case highlights the potential for parasitic infections, specifically malaria, to cause significant interference in automated platelet counting.
• Systematic examination of stained blood films and employing reference methods like immunological platelet counts or phase-contrast microscopy are essential for accurate diagnosis in suspected interference cases.
• Accurate platelet counts are critical for managing conditions like malaria and preventing complications associated with thrombocytopenia.