A phlebotomist finishes collecting a sample for a complete blood count (CBC) from a newborn using a heelstick collection and a microtainer containing ethylenediaminetetraacetic acid (EDTA). Assume the sample is collected exactly according to procedures established by the laboratory. As he or she is leaving the nursery, the child's nurse asks if a calcium draw may be added on-to be done from the same specimen already collected. The phlebotomist does not wish to subject the newborn to another collection, so he or she adds the calcium on to the tests already on the requisition. This action will result in which of the following outcomes?

Question

Quizplus · Accepted Answer

EDTA is an anticoagulant that binds calcium, so any test that requires calcium measurement cannot be accurately performed on a sample containing EDTA. Adding a calcium draw to the same specimen already collected with EDTA will result in a falsely decreased calcium result. The other test results (white cell count and hemoglobin level in the CBC) will not be affected by adding a calcium draw.

A Phlebotomist Finishes Collecting a Sample for a Complete Blood