Patients with both end-stage renal disease and multiple myeloma are prone to changes in ionized calcium homeostasis that may have grave consequences. However, only total calcium level is reported in most routine laboratory testing, with various algorithms used to derive the physiologically important ionized or free calcium level to guide treatment. We studied a patient with multiple myeloma undergoing long-term hemodialysis who presented with a markedly elevated total calcium level but with only minimal elevation in the ionized calcium level. All of the commonly used algorithms would have overestimated the ionized calcium level, and some of these might have led to inappropriate treatment. When therapy depends critically on the ionized calcium level, direct measurement is essential.
(Arch Intern Med. 1992;152:1321-1322)
Nora NA, Singer I. Interpretation of Hypercalcemia in a Patient With End-Stage Renal Disease. Arch Intern Med. 1992;152(6):1321–1322. doi:10.1001/archinte.1992.00400180159027
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