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Specimen Type: Serum, Heparin Plasma
Optimum Volume: 1 mL
|3 weeks||8 months||1 year|
Reporting units: mg/dL
Biological or Clinical Significance:
Calcium is the major material used in mineralization of bones. The calcium content of an adult is somewhat over 1 kg (25000 mmol), i.e. about 2% of the body weight. Of this, 99% is present as calcium hydroxyapatite in bones and less than 1% is present in the extraosseous ICS (intracellular space) or ECS (extracellular space). The calcium level in the ECS (approx.100 mmol) is in dynamic equilibrium with the rapidly exchangeable fraction of bone calcium. Calcium ions affect the contractility of the heart and the skeletal musculature and are essential for the function of the nervous system. In addition, calcium ions play an important role in blood clotting and bone mineralization. In plasma, calcium is bound to a considerable extent to proteins (approx.40%), 10% is in the form of inorganic complexes and 50% is present as free (ionized) calcium. The body ’s calcium balance is regulated by the parathyroid hormone (PTH), calcitriol (CT) and calcitonin.
The measurement of calcium is used for the diagnosis and monitoring of hypocalcemia and hypercalcemia in serum. The characteristic symptom of hypocalcemia is latent or manifest tetany and osteomalacia. Hypercalcemia is primarily brought about by increased mobilization of calcium from the skeletal system (osteoporosis) or increased intestinal absorption.
The main significance of determining urinary calcium lies in the differentiation between hypercalciuria and hypocalciuria and the differential diagnosis of nephrolithiasis.
Principle of Test Method:
The calcium assay is an automated colorimetric method.