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Preanalytic Variables in Special Coagulation Testing

Clinical Implications

Normal Hematocrit and High Hematocrit

Slide 8

October 2008

This slide shows a cartoon of a specimen collection tube containing citrate anticoagulant. This is just a diagrammatic representation.

When a patient sample is collected the citrate anticoagulant will typically be mixed in and not visible as a discrete layer. The amount of citrate anticoagulant present in commercially available collection tubes is calculated to result in a ratio of 1 part anticoagulant to 9 parts whole blood or 1 part anticoagulant to 5 parts of plasma, as shown.

The tube shown on the left represents a typical blood sample from a patient with a normal hematocrit. The tube on the right, however, represents a sample from a patient with an elevated hematocrit, such as the patient I have just described.

In this situation, even the increase hematocrit there is a relative reduction in the amount plasma collected in the tube, and therefore, there is a relative excess of anticoagulant which elates an excessive amount of calcium.

Normal and High Hematocrit


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