This word (Serum" in medical terms means the liquid part of human blood.
In the laboratory, blood samples are separated using a laboratory equipment called a centrifuge. The centrifugation process results in the blood sample being separated into three layers, the upper part of which is called the serum.
Serum from a blood sample contains water and all the chemicals dissolved in our blood, including proteins, hormones, enzymes, vitamins, and even harmful substances such as urea.
Therefore, if we separate the blood sample, we remove all the blood cells from it, in addition to the proteins that cause blood clotting, and the separated watery part is called the serum. It is called plasma if we use a substance that prevents clotting, and thus the blood separated by centrifugation becomes divided into liquid plasma that includes water, chemicals, and clotting factors, and at the bottom there is an agglomeration of white and red blood cells and platelets.
Therefore, in laboratory tests that use serum to determine the result, the word “serum” or the letter “S” is written before the name of the test, to infer that the final result depends on the level or concentration of the substance that we measure in the patient’s serum.
Example: When a doctor orders a laboratory test and writes it down to "serum calcium test", it means that what is required is to measure the level of calcium in the patient’s serum and not in the entire blood drawn from the patient.
Sometimes adding the word “serum” or the letter “S” may not mean any laboratory meaning. An illustrative example: If the doctor requests a laboratory urea test and writes “blood urea level” it means that he does not necessarily want the laboratory to measure the urea level in the patient’s entire blood and not just the serum, because this test is done in the laboratory using serum.
There are many laboratory tests in which the serum is used, such as: serum kidney function test, serum liver function test, heart function, and thyroid level.
Laboratory tests for which it is not appropriate to use serum, such as: complete blood count or complete blood count, anemia level, blood group test, and a test to measure prothrombin time and concentration.
Tests can be done from either serum or plasma, such as: blood pregnancy test, HIV test, and HIV test.
Lab tests that doctor write it down in either ways: blood calcium and serum calcium test, blood glucose level and serum glucose test.
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