In hematology, clots in an EDTA blood sample are:

• A. Acceptable if they are microscopic
• B. Acceptable if detected on a wooden stick only
• C. Acceptable if run through an automatic analyzer
• D. Never acceptable

Answer: (D)

A clot in an EDTA blood sample means the anticoagulant did not prevent coagulation, so the specimen isn’t in true whole-blood form. EDTA works by binding calcium to stop clotting, and when a clot forms, cells aren’t evenly suspended, platelet counts can be distorted, and automated analyzers can give inaccurate results or fail. For hematology, especially CBCs, you need a well-mixed, unclotted sample, so any clot renders the specimen unusable. Therefore clots are never acceptable in EDTA blood samples. There’s no circumstance in which a clot could be considered acceptable, even if it’s microscopic or observed after certain handling; recollection with proper technique is required.