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Artefactually-normal automated platelet counts due to malaria-infected RBC
G Crabbe1, M Van Poucke, B Cantinieaux
1CHU Saint-Pierre, ULB. VUB, 322 rue Haute Brussels 1000, Belgium.
Abstract:
Protein aggregates, red cell or white cell fragments are known to interfere with platelet counts in automated blood analysers, both by aperture impedance and optical technologies. When a falsely high value is suspected, interference by pseudo-platelet particles can be confirmed by systematic examination of stained blood films. The method that best avoids these sources of interference is the reference, immunological platelet count. We describe a case of treated malaria with a false normal platelet count. The blood smear revealed small red cells, infected by trophozoites of Plasmodium falciparum, that interfered with the platelet count. The Cell Dyn 4000 shows different patterns of interference by infected red cells in its impedance and optical counts, and thrombocytopenia was suspected immediately. This was confirmed by a phase-contrast microscopic platelet count.
Insights
Automated blood analyzers can miscount platelets due to red blood cell fragments, especially in malaria cases. Microscopic examination and immunological platelet counts are crucial for accurate diagnosis when automated systems show discrepancies.
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.
