Specimen HandlingQuestion 68 of 100
An EDTA specimen is collected for a CBC with a manual differential. What time limit applies to making the blood smear?
a.Smears must be made after refrigerating the tube overnight
b.Smears may be made up to 24 hours later at room temperature
c.Smears should be prepared within about one hour of collection
d.Timing does not matter because EDTA preserves morphology indefinitely
Explanation
EDTA preserves cells for automated counting for roughly 24 hours, but white cell and platelet morphology begins to distort within a few hours, so smears are made within about one hour. Waiting a day produces artifacts that mimic disease. Refrigeration does not restore morphology, and no anticoagulant preserves cell shape indefinitely.
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