Assessment

Test

Abnormality with Normal Result Condition

Explanation

Serum calcium: 8.6-10.3

total calcium mg/dL

including free ionized calcium and calcium bound with protein or organic ions

Accumulation of calcium above normal levels in the extracellular fluid compartment; clinical manifestations generally occur when calcium levels are above

12 mg/dL and tend to be more severe if hypercalcemia develops rapidly; if ionized calcium cannot be measured, total serum calcium can be corrected by

Diagnostic Highlights (continued)

Test

Normal Result

Abnormality with Condition

Explanation

Serum ionized calcium: unbound calcium; level unaffected by albumin level

Serum parathyroid hormone level

10-65 pg/mL

Elevated in more than 90% of people with primary hyperparathyroidism adding 0.8 mg/dL to the total calcium level for every 1 g/dL decrease of serum albumin below 4 g/dL; the corrected value determines whether true hypocalcemia is present. When calcium levels are reported as high or low, calculate the actual level of calcium by the following formula: Corrected total calcium (mg/dL) = (measured total calcium mg/dL) + 0.8 (4.4 - measured albumin g/dL)

Ionized calcium is approximately 46%-50% of circulating calcium and is the form of calcium available for enzymatic reactions and neuromuscular function; levels increase and decrease with blood pH levels; for every 0.1 pH decrease ionized calcium increases 1.5%-2.5%

Determines presence of hyperpara-thyroidism

Other Tests: Electrocardiogram (shortened QT interval), urine calcium clearance.

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