Occasionally someone will collect a specimen in EDTA only to find that the test requires a different specimen type. A problem arises when the person pours the EDTA sample into a serum tube rather than returning to draw a new specimen.
Features in the laboratory:
(1) undetectable calcium and magnesium (due to chelation by the EDTA)
(2) supraphysiologic levels of potassium (due to the potassium salt of EDTA)
(3) fibrinogen normal (should be very low in a serum sample due to clotting)
(4) there should be no fibrin clot in the bottom of the original serum tube
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