Why does serum clot

The clotting process activates a cascade of proteases, which results in the conversion of prothrombin to thrombin, an enzyme that converts fibrinogen into fibrin to clot blood. Platelets are activated in the process and release a set of compounds, which naturally alters proteins in the serum. To collect plasma, an anticoagulant is added to the centrifuged whole blood, which can impact testing. EDTA is the most commonly used anticoagulant in clinical diagnostic labs.

EDTA chelates the calcium needed for clotting, but can also inhibit other enzymes. There are many other anticoagulants in use such as citrate, heparin, and fluoride, each with appropriate uses.

If you use only one, you could be misled by false results. For example, clotting factors in serum or the platelets and cellular elements that contaminate plasma could interfere with or alter your results. If your results are the same for serum and plasma, then you have more flexibility in sample usage. View all of our available serum and plasma samples , including normal donors, diabetic donors, RA donors, SLE donors, and donors with other disease states.

She has a strong background in cell-based therapeutics and immunology, including a Ph. Learn more about Dr. Why is plasma volume more than serum volume in blood? I think that may be a technical difference, not an actual difference in volume.

You can get more serum if you allow the clot to contract, which it will do over the course of an hour or so. The segments of tubing used to transfer separated plasma from the red cells can sometimes be obtained from vendors of outdated plasma. These segments contain about uL of plasma and are invaluable for informal normal-range studies as they come from ostensibly healthy normal donors, who can be identified by age and gender. The entire bag of plasma associated with the tubing segments may also be available for further studies, and it holds approx.

This can be a valuable resource in the process of developing an assay. Labs usually have time limits on how long serum or plasma can remain in touch with the red blood cells before being physically separated—usually by pouring off into another tube—while maintaining the identity of the patient from whom the blood was taken.

This is necessary because RBCs can rupture over time, and the contents can interfere with a number of assays. RBCs contain high levels of potassium and the thyroid hormone thyroxine. Assays for either of these substances and others can be skewed by the contents of lysed red blood cells. Hemoglobin is the most abundant protein in blood. It can interfere in assays once released from RBCs. One technical solution to the problem of RBCs remaining in contact with the serum or plasma is to use serum separator tubes SSTs.

These are evacuated blood drawing tubes that contain a silicone gel that has a density intermediate between serum and red blood cells. In a centrifuge, this silicone gel forms an impermeable layer between the red blood cells at the bottom of the tube and the serum above. Caution is advised in using these SSTs with hydrophobic analytes such as some drugs. Whole blood, serum, and various plasmas are not interchangeable sample matrices.

While some analytes may give similar results, equivalence can only be ensured by testing matched samples. Some analytes, such as Parathyroid Hormone PTH , partition freely between the red blood cells and the plasma so that whole blood and plasma values are the same within experimental accuracy. We thank the Department of Obstetrics and Gynecology fertility laboratory at the Medical College of Virginia Hospitals for measuring some of the analytes and Carol Rodgers for performing the stability test of LD on the pneumatic tube system.

Tietz textbook of clinical chemistry 2nd ed. Changes in serum chemical values as a result of prolonged contact with the clot. Am J Clin Path ; 66 : Serum-constituents analyses: effect of duration and temperature of storage of clotted blood. Clin Chem ; 27 : 35 Effect of three-day clot contact on results of common biochemical tests with serum. Clin Chem ; 32 : Storage of whole blood: effect of temperature on the measured concentration of analytes in serum.

Clin Chem ; 34 : Storage of serum or whole blood samples? Effects of time and temperature on 22 serum analytes. Eur J Clin Chem Biochem ; 33 : Shewhart, WA. Economic control of quality of manufactured product. New York: D. Van Nostrand, pp.. Montgomery, DC. Introduction to statistical quality control, 3rd ed.

New York: John Wiley and Sons, pp.. Fraser CG. The application of theoretical goals based on biological variation data in proficiency testing. Arch Pathol Lab Med ; : Biological variation in clinical chemistry.

Tonks DB. A study of the accuracy and precision of clinical chemistry determinations in Canadian laboratories. Clin Chem ; 9 : Eficia de un programa interno de control de calidad. Quim Clin ; 5 : Tolstoi E. Glycolysis in bloods of normal subjects and of diabetic patients. J Biol Chem ; 60 : Manual of American Society of Clinical Pathologists workshop on glucose. Am J Clin Pathol ; 26 : Effectiveness of sodium fluoride as a preservative of glucose in blood.

Clin Chem ; 35 : Danowski TS. The transfer of potassium across the human blood cell membrane. J Biol Chem ; : Serum potassium changes in blood clots. Am J Clin Pathol ; 24 : Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide.

Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract. Materials and Methods. Effect of serum-clot contact time on clinical chemistry laboratory results. Departments of Pathology and. Oxford Academic. Google Scholar. R K Elswick. W Greg Miller. Fax ; e-mail millerg hsc. Jimmy L Bailey. American Medical Laboratories. Select Format Select format.

Permissions Icon Permissions. Abstract The effect of serum-clot contact time on laboratory results was studied by dividing each blood specimen into four blood collection tubes.

As the plasma races around the body, cells will deposit their waste into the plasma, which contributes to another job of the plasma: waste removal. Put simply, serum is plasma minus the clotting factors and blood cells. During the process of removing the clotting factors achieved by centrifugation , the protein fibrinogen as described above is converted to fibrin.

Fibrin is an insoluble protein that is used to assist in the repair of tissue damage by forming a clot over the wound which acts to hinder the flow of blood.