NHA Phlebotomy Certification Practice Exam

What is the main anticoagulant used for coagulation studies?

1. ethylenediaminetetraacetic acid (EDTA)

2. sodium citrate

3. heparin

4. oxalate

The correct answer is: sodium citrate

The main anticoagulant used for coagulation studies is sodium citrate. This anticoagulant works by chelating calcium, which is necessary for the coagulation process. By binding calcium ions, sodium citrate effectively prevents blood from clotting. This is particularly important in coagulation studies, as it allows for accurate measurement of various clotting factors and the body's overall hemostatic function. When performing tests such as prothrombin time (PT) and activated partial thromboplastin time (aPTT), the blood must remain free of clots to ensure that the tests reflect the true coagulation status of the patient. Sodium citrate is specifically used for this purpose because its effects can be reversed by adding calcium back into the sample after testing, allowing for additional analyses if necessary. Other anticoagulants mentioned have their specific uses but are not preferred for coagulation studies. For instance, EDTA is commonly used for complete blood counts because it does not interfere with cellular components, while heparin is used in other scenarios like for plasma assays or in certain situations in blood transfusion procedures. Oxalate is not typically used for coagulation studies either, as it can inhibit the activity of some coagulation factors.