The ionized calcium is determined by an ion selective electrode methodology. The result that is generated is pH adjusted. The result is empirically based on a measured pH and ionized calcium concentration normalized to a pH of 7.40. This calculation compensates for in vitro changes in pH due to loss of CO2 through specimen handling. Ionized calcium represents the true "bioavailable" calcium in the circulation. In situations where the total calcium is normal but does not fit the clinical picture, e.g., hyperparathyroidism, a determination of the ionized calcium will, many times, show an elevation in the "bioavailable" calcium component. This may be due to alterations in protein concentrations, especially albumin, that binds most of the calcium in the circulation.
Significant deviations from the normal range may require further evaluation by your physician.
This test is used to evaluate nonbound calcium, calcium metabolism, physiologically active calcium fraction, hyperparathyroidism, ectopic hyperparathyroidism. This test is occasionally useful when hypercalcemia coexists with abnormal protein state such as myeloma. Also useful in assessing active calcium fraction in hypoproteinemia and acidosis when calcium is low.
Calcium, Ionized, Serum is also known as Ca++, Ionized, Serum; Calcium Filterable, Serum; Calcium Free, Serum; Calcium Unbound, Serum; Ionized Calcium, Serum
No fasting required.
Estimated turnaround for results is 3 business days. If confirmation testing is required, the estimated time may be extended.
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