Correction Algorithm of Pseudothrombocytopenia due to Platelet Clumping

Oh, Bong Joon; Cho, Duck; Kee, Seung Jung; Shin, Myung Geun; Shin, Jong Hee; Suh, Soon Pal; Ryang, Dong Wook

Abstract

BACKGROUND
Pseudothrombocytopenia is a phenomenon that automated hematology analyzers calculate platelets at a spuriously low count. The most common cause of this phenomenon is platelet clumping. Several methods such as vortex mixing, changing anticoagulant to sodium citrate or heparin, and adding amikacin to ethylenediaminetetraacetic acid (EDTA) have been routinely used for managing pseudothrombocytopenia. The purposes of this study were to compare the efficacy of these four methods and to propose a cost-effective algorithm for managing pseudothrombocytopenia in clinical laboratories. METHODS: Ten patients (six males and four females) having pseudothrombocytopenia were evaluated. In these patients, platelet clumpings had been detected on more than three occasions by Coulter STKS (Beckman-Coulter, USA) and by microscopic examination on peripheral blood smear (PBS). We recollected blood samples from each patient in four tubes coated with EDTA, sodium citrate, heparin, or EDTA with amikacin. CBC of the blood samples in each tube was performed within one hour of collection; the samples in EDTA-coated tube were retested after vortex mixing. RESULTS: Platelet counts were increased in all cases (100%) by EDTA with amikacin as an anticoagulant, 80% (8/10) by vortex mixing or heparin, and in 90% (9/10) by sodium citrate. However, platelet counts were decreased in 20% (2/10) of heparin coated samples. `Clinically meaningful increase' was achieved in 60% (6/10) by heparin and EDTA with amikacin, in 50% (5/10) by sodium citrate, and in 40% (4/10) by vortex mixing. But `clinically meaningful decrease' was found in 10% (1/10) by heparin. CONCLUSIONS: When pseudothrombocytopenia due to platelet clumpings is detected, vortex mixing is recommended first. If platelet count does not increase after the vortex mixing, changing anticoagulant to sodium-citrate or adding amikacin to EDTA is recommended for managing pseudothrombocytopenia.