If K2EDTA is collected before serum or a light-blue tube, which tests are erroneous?

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Multiple Choice

If K2EDTA is collected before serum or a light-blue tube, which tests are erroneous?

Explanation:
When K2EDTA is carried into the sample before serum separation, EDTA acts as a potent chelating agent for divalent ions and also contributes potassium from the salt form. This shifts the measured values in the direction of the additive’s chemistry: calcium and magnesium are bound by EDTA, so their apparent concentrations fall, while the potassium level rises because the EDTA compound itself contains potassium. Sodium is not directly affected by EDTA in the same way, so it doesn’t follow the same pattern of change. Therefore, the erroneous pattern you’d expect from this draw order is low calcium and magnesium with high potassium.

When K2EDTA is carried into the sample before serum separation, EDTA acts as a potent chelating agent for divalent ions and also contributes potassium from the salt form. This shifts the measured values in the direction of the additive’s chemistry: calcium and magnesium are bound by EDTA, so their apparent concentrations fall, while the potassium level rises because the EDTA compound itself contains potassium. Sodium is not directly affected by EDTA in the same way, so it doesn’t follow the same pattern of change. Therefore, the erroneous pattern you’d expect from this draw order is low calcium and magnesium with high potassium.

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