Final answer:
To accurately assess total serum calcium, serum protein levels must be measured due to the significant amount of calcium bound to these proteins.
Step-by-step explanation:
To determine an accurate total serum calcium level, the laboratory should simultaneously measure serum protein levels. This is important because about 35-45% of calcium in the blood is bound to proteins, mostly to albumin. Any decrease in plasma proteins will be accompanied by a decrease in the total calcium level. Also, it's essential to consider that serum calcium exists in equilibrium with calcium complexed to various substances including proteins and blood pH can influence ionized calcium levels.