Certified Tissue Bank Specialist (CTBS) Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

Albumin is classified as a colloid because it is a protein solution that contains large molecules capable of exerting oncotic pressure in the bloodstream. Colloids, by definition, are mixtures where tiny particles (in this case, proteins like albumin) are suspended in a fluid medium, which can help maintain blood volume and pressure.

Colloids are particularly effective in drawing water into the circulatory system, which is essential during fluid resuscitation or in conditions where blood volume needs to be increased. Albumin, being a natural protein found in blood, is often used in medical settings for this purpose.

The other substances listed do not meet the criteria for colloids: normal saline and lactated ringers are classified as crystalloids, consisting of small molecules that readily cross cell membranes and do not exert significant oncotic pressure. Whole blood contains both cellular components and plasma but is not typically classified solely as a colloid, as the presence of cells complicates its classification.