Prealbumin Vs. Albumin

Both albumin and prealbumin are indicators of protein nutrition. Let us find out the similarities and differences between these two serum proteins.
Protein deficiency is one of the serious nutritional deficiencies. It can seriously impair body's ability to fight infections and heal. Protein deficiency must be cured before a person undergoes a surgery or a treatment for injury is initiated. A test for protein deficiency is done by checking the levels of two protein serums namely, albumin and prealbumin. The levels of these proteins are considered good indicators of the degree of malnutrition. However, both these proteins differ from each other in many ways.
Prealbumin and albumin levels allow the practitioners to study the extent of malnutrition and devise a course of treatment. Making necessary changes to the nutrition of a patient shows faster recovery and better healing. Let us compare the two protein serums against various parameters.
Both albumin and prealbumin are synthesized by hepatocytes or cells of liver. Prealbumin is essentially a tryptophan rich protein. Albumin is the most abundantly found blood protein in the body and constitutes for about 50% of total protein serums. Needless to say, levels of albumin are a major determinant in protein deficiency.
The most important function of albumin is to maintain colloidal osmotic pressure, in order to keep the fluids securely inside the vascular space. Low levels of albumin may lead to edema, ascites or pulmonary edema. Albumin is also concerned with transportation and absorption of zinc in the body. Prealbumin functions as a binding agent and transports protein in the blood. Prealbumin is not a precursor to albumin, as the name wrongly implies. In fact, the real name of prealbumin is transthyretin.
Half Life
Albumin has a half life of about 20 days whereas prealbumin has a half life of about 2 days. Besides, albumin has a large serum pool, whereas prealbumin has small serum pool. This is the reason why low albumin levels often translate to a significant loss of serum pool. The shorter half life of prealbumin makes it more sensitive to protein deficiency. It is also more reliable than albumin when it comes to detecting low protein levels.
Due to very long half life of albumin, it is not considered as a very good indicator of serum loss. This means, albumin levels remain elevated, even though there is serum loss. By the time, a drop in albumin levels is detected, too much of serum loss has already occurred. Prealbumin with its shorter half life can be a good indicator of serum loss. Both albumin and prealbumin are negative acute-phase reactants, meaning the changes in protein nutrition are reflected slowly. Thus, when a person is treated for protein malnutrition, it may take 2 - 3 weeks for his albumin levels to show any change. Hence, there is no way of knowing if the reduced levels are due to inadequate nutrition or stress or any other complications.
Although, albumin and prealbumin are not very good indicators of nutritional screenings, they are indeed very effective in keeping a tab on protein serum levels in the long run. Albumin, especially, can make a lot of difference to body's ability to heal, due to its large serum pool. Regular screenings of albumin and prealbumin can help cure protein nutrition deficiencies at the earliest. People suspected of having protein nutrition deficiencies must get themselves screened for prealbumin levels for faster diagnosis.
Prealbumin and albumin levels can be tested at any medical setting at an affordable cost. These tests are usually recommended by physicians for the diagnosis of a possible medical condition. In such cases, you may have to undergo other serum tests in addition to albumin and prealbumin tests.