Interpreting blood smears (or what blood smears are trying to tell you!)

Anticoagulant induced artefacts in peripheral blood smears

Microscopic evaluation of a peripheral blood smear is one of the most beneficial test. But anticoagulant induced artefacts could lead to misinterpretation of the smears. The present study was undertaken to identify the anticoagulant induced artefacts and avoid misinterpretation of peripheral blood smears. The blood samples were collected using Ethylene Diaminetetraacetic acid (EDTA) and Sodium citrate, mixed thoroughly and smears were made immediately as well as 1hr apart for 6 hrs, stained and examined under oil immersion microscope. Direct smears were used as controls. Significant morphological artefacts were observed in our study. Artefacts were marked at the end of 2 hrs with EDTA but seen almost immediately with citrate blood. At 6 hrs, artefacts were marked but more severe with citrates than EDTA. Thus the practice of making blood smears before addition of anticoagulant is recommended and a delay up to 1hr is permissible with EDTA blood but not beyond.