The Calcium Assay

Written by: Solaris Diagnostics

The Calcium Assay is an in vitro test used for the quantitative determination of calcium in human serum, plasma, and urine. Calcium holds vital roles in muscle contraction, hormone secretion, glycogen metabolism, bone mineralization, nerve impulse transmission, and blood coagulation. Detection of abnormal blood calcium levels may assist in the diagnosis of variety of issues including parathyroid disease, bone diseases, renal failure, malnutrition and malabsorption syndrome, and vitamin D deficiency. Additionally, calcium levels in urine can reflect calcium intake, intestinal and skeletal absorption, and kidney function.

Calcium is the fifth most common element in the human body and is primarily found in bone. In fact, 99% of calcium in the human body is in bone, while the other 1% remains circulating in blood. The body closely maintains calcium levels, so much so that if too little calcium is present in the blood, calcium is taken from bone in order to maintain appropriate blood calcium levels. About half of the calcium in the blood is metabolically inactive and is bound to proteins, like albumin, or complexed to ions, while the other half is metabolically active and considered free, or unbound. A total calcium test accounts for both the free and bound forms of calcium. This test is usually a good reflection of the amount of free calcium in the blood because the balance of free and bound calcium is generally stable, and each is typically about half of the total calcium. A calcium test may also be performed with other tests like parathyroid hormone (PTH) or vitamin D, which help regulate blood calcium concentrations through a feedback loop. When regulation of calcium is disrupted, this can lead to hypercalcemia (increased calcium) or hypocalcemia (decreased calcium), which can lead to a variety of symptoms including problems with the central nervous system, fatigue, kidney stone formation, and depression.

At Solaris Diagnostics, calcium is measured using photometric technology on an Atellica CH Analyzer. The test method requires assay-specific reagents in order to generate a reaction and a photometer which measures light absorbances before and after the reaction. These absorbances are then converted into quantitative results. Solaris Diagnostics can provide calcium results within 24 hours from the time the sample is received in the laboratory.

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