ABSTRACT
BACKGROUND: Platelet clumping is a common cause of erroneous platelet counts by automated blood cell counter. The most commonly employed solution to this problem is to redraw the specimen into a different anticoagulant. However, this is unpleasant for the patient and not rapid for reporting of the corrected platelet count. Mixing of blood with a vortex mixer was evaluated as a method to disaggregate platelet clumps in blood and thus obtain accurate platelet counts. METHODS: Whole blood samples coated with ethylenediaminetetraacetic acid (EDTA) from 28 patients with platelet clumping and 20 controls without platelet clumping from July to September 2002 were mixed for 30 seconds with a vortex mixer. Platelet counts, blood smears, erythrocyte counts, Hgb, MCV and total leukocyte counts were evaluated before and after mixing. RESULTS: Vortex mixing of blood samples with platelet clumps caused an increased platelet count in 96% (27/28) and a decreased total leukocyte count in 68% (19/28). The mean platelet and total leukocyte counts of 28 blood samples before mixing were 155.0+/-89.6 (x10(3)/microL) and 12.9+/-5.5 (x10(3)/microL) and after mixing they were 249.2+/-116.2 (x10(3)/microL) and 12.0+/-5.4 (x10(3)/microL). Total erythrocyte counts, Hgb, MCV were not significantly affected by vortex mixing. Further, vortex mixing of 20 control samples had no consistent effect on each items. CONCLUSIONS: Vortex mixing of blood samples is a simple, rapid method without re-sampling in correction of erroneous platelet count induced by platelet clumps.