2007-01-28 11:41:18 · 2 answers · asked by fiona w 1 in Science & Mathematics ➔ Medicine
chelation of calcium prevents clotting because calcium ions are required to convert fibrinogen to fibrin
2007-01-28 11:58:25 · answer #1 · answered by davidosterberg1 6 · 3⤊ 0⤋
Calcium is in the common pathway of the coagulation cascade.
Sodium Citrate is the anticoagulant in that blue top tube that Coagulation tests such as PT (extrinsic factor) and aPTT (instrinsic factor) are performed out of.
The sodium citrate chelates the Ca++ and halts the fall of the coagulation cascade.
When the tests are performed, one of the reagents on the analyzer is Calcium Chloride (CaCl2). In the case of the aPTT test, a Phospholipid and CaCl2 is added to the citrated plasma to restart, if you will, the coagulation cascade. Time is measured in seconds how quickly clot formation is formed.
For the PT, Thromboplastin is added to the sample. Time again measured in seconds, how quickly the clot forms.
2007-01-30 01:16:16 · answer #2 · answered by Rat 4 · 0⤊ 0⤋