EDTA induced clumping of platelets

 EDTA induced clumping of platelets leading to underestimation of platelets on automated cell counters (pseudo thrombocytopenia) is a common occurrence. The pathologist must check smear to rule out this. The peripheral smear shows large clumps of platelets particularly at the periphery of smear. 

Fig: EDTA induced clumps of platelets seen on peripheral smear. (Pseudo thrombocytopenia)

For such patients a repeat sample in heparin should be taken for estimation of platelets count.