Calcium (Ionized), Whole Blood

Direct vs. Reflexive Ionized Calcium Testing

Calcium testing is useful for investigating disorders involving the parathryoid-vitamin D-calcium endocrine system. Testing is indicated for patients with documented or suspected derangements in this system, but there is little evidence to suggest that screening unselected patients with calcium testing is useful, even in critically ill patients. Standing orders for monitoring ionized or total calcium and replacing with calcium gluconate in patients WITHOUT documented or suspected calcium disorders is unlikely to be of benefit, and may lead to poorer outcomes (see references below).

In order to detect clinically-significant hypo- and hyper-calcemia in hospitalized patients, please use Calcium (Reflexive Ionized) [ICAR] or Basic Metabolic Panel with Reflexive Ionized Calcium [BMPICR]. In this test panel, a patient receives a total calcium test first, and if the result is <8 mg/dL or >10.2mg/dL, an ionized calcium test is performed on the same plasma sample. The test panel was developed as an alternative to daily ionized calcium testing in patients hospitalized at UW and Harborview Medical Centers, a largely unnecessary practice that was associated with excessive calcium therapy.

Calcium (Ionized), Whole Blood [WIC] is intended for patients in whom a calcium metabolic derangement has ALREADY been detected and in whom the calcium concentration needs to be followed, i.e. in post-surgical hypoparathyroidism. Additionally, nonreflexive ionized calcium testing is useful when the total calcium is not expected to correlate well with ionized calcium concentrations, i.e. hypo- or hyper- proteinemia or albuminemia, altered pH, and high concentrations of calcium binding substances like citrate anticoagulants.