The falsely depressed total calcium result can result in:
(1) a normocalcemic patient being diagnosed as hypocalcemic
(2) a hypercalcemic patient being diagnosed as normocalcemic
Laboratory method affected: colorimetric assay for calcium
Contrast medium implicated:
(1) gadodiamide (Omniscan)
(2) gadoversetamide (OptiMARK)
Contrast medium not reported to cause this problem:
(1) gadopentetate dimeglumine (Magnevist)
(2) gadoteridol (ProHance)
Patients at risk for a problem:
(1) patients in the ICU (more laboratory testing done in period after an MRI)
(2) high dose (>= 0.2 mmol per kg body weight, > 20 mL) of contrast agent administered
(3) renal insufficiency (decreased excretion)
A person with normal renal function may be affected for the 12 hours after receiving the contrast agent. A patient with renal insufficiency may be affected for 24 hours.
Methods of handling:
(1) Use of a contrast agent that does not cause a falsely depressed total serum calcium level.
(2) Measure ionized calcium or total calcium by a noncolorimetric assay if in doubt.
(3) Delay measurement of total serum calcium until the contrast agent is cleared.
