Is sample collection really critical for lupus testing?
Yes. Besides heparin contamination, other pretest variables may have a significant impact on detecting the lupus anticoagulant. The blood sample is collected in a special citrated tube and centrifuged to remove the plasma (liquid part) for testing. There must be the proper amount of blood in the tube and it cannot be clotted. When the blood is centrifuged most of the platelets are left behind. If there are too many in the plasma sample, it may be compromised (because platelets are a source of phospholipids). Also, if the patient’s haematocrit (the amount of solid components in their blood) is elevated or decreased test results may be affected.
