Which tube color is used for calcium testing?

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Multiple Choice

Which tube color is used for calcium testing?

Calcium testing needs a tube whose additive won’t bind or alter calcium in the sample. Lavender (EDTA) and grey (fluoride-oxalate) tubes use chelating additives that grab calcium, which skews the result. Green-top tubes contain heparin, which prevents clotting without chelating calcium, so the calcium level can be measured accurately. This is why calcium testing is performed in a green-top tube. Red-top tubes can yield serum calcium, but green-top tubes are standard when plasma calcium is being tested.

Calcium testing needs a tube whose additive won’t bind or alter calcium in the sample. Lavender (EDTA) and grey (fluoride-oxalate) tubes use chelating additives that grab calcium, which skews the result. Green-top tubes contain heparin, which prevents clotting without chelating calcium, so the calcium level can be measured accurately. This is why calcium testing is performed in a green-top tube. Red-top tubes can yield serum calcium, but green-top tubes are standard when plasma calcium is being tested.

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