When EDTA anticoagulated blood cannot be tested within 1–2 hours, it must be refrigerated at 4–8 C to prevent cellular changes affecting test results.
Manual or automated blood cell counts, reticulocyte counts, and PCV change little in EDTA blood at
4–8 C when stored for up to 24 hours. Haemoglobin concentration is stable for 2–3 days at 4–8 C providing there is no haemolysis
Blood films:
In EDTA anticoagulated blood, morphological blood cell changes occur soon after blood is collected when it is stored at room temperature (18–25 C) and within 3 hours when stored at
4–8 C.
It is therefore recommended that blood films be made and methanol-fixed as soon as possible after blood is collected and never made after overnight storage. Some of the blood cell changes which occur in EDTA blood include:
● Neutrophil degeneration with neutrophils
becoming more irregular in shape, nuclear lobes separating, and vacuoles appearing in the cytoplasm. There is also loss of granules.
● Segmentation (budding) of the nucleus of lymphocytes and monocytes and vacuoles appearing in the cytoplasm.
● Erythrocytes becoming crenated and spherocytic.
● Platelets disintegrating.
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