This was drawn for an ENOX2 test. The patient had mildly elevated Calcium, TP, Albumin, and ALT. All other labs were normal except a chronically high Lp(a).
Patient developed Shingles at about the same time.
Water without solutes will freeze at
zero degrees C. The presence of any solutes and their concentration will further depress freezing point below zero degrees C. This applies to serum or plasma
I agree with Dantham's answer. This phenomenon reflects coligative properties of solutions in comparison with pure solvents. In case of plasma or serum, pure solvent is water and all mineral and organic components of plasma/serum are solutes. The more particles of solutes are in a solution, the lower is the freezing point of a solution relative to the pure solvent. On the other hand, the more particles of solutes are in a solution, the higher is the boiling point of a solution relative to solvent. To sum up, solutes decrease freezing point and increase boiling point of a solvent.
In case of less comlex solutions, sometimes you can get a supercooled state,. In this case, if you just lightly shake the tube it will freeze right in your hand ! In case of FBS, I would add that you should make sure your freezer is at -20C to get it to freeze. The door of these freezers is much warmer than the inside, especially if you keep opening the freezer often, and even PBS solutions sometimes do not freeze. In the latter case, then you know it is not keeping temperature.