ABSTRACT
The calcium reported in the standard veterinary serum biochemical profile is the total calcium, which is made up of biologically active ionized calcium (approximately 50% of the total under normal circumstances), calcium complexed to anions such as citrate, bicarbonate, lactate, or phosphate (approximately 5%), and protein-bound calcium that is associated primarily with albumin and to a lesser extent, globulins (approximately 45%) (Rosol). Various physiological parameters such as serum protein concentration and pH may influence the proportions of the different fractions, and proportions may be unpredictable in some conditions such as renal failure (Schenck). Some disease conditions may alter total serum calcium, but not impact the biologically active fraction, whereas other conditions may be characterized by normal total serum calcium but changes in the ionized fraction. Therefore, it may be informative to measure ionized calcium in some patients. This requires specialized sample handling and instrumentation (ion specific electrode).
