Gadodiamide administration causes spurious hypocalcemia.
OBJECTIVE
To evaluate the prevalence of spurious hypocalcemia after gadodiamide-enhanced magnetic resonance (MR) imaging.


METHODS
Eight hundred ninety-six inpatients with available serum calcium data obtained before and after gadodiamide-enhanced MR imaging were identified. Changes in serum calcium measurements following gadodiamide administration in 1,049 MR imaging examinations performed in these patients were correlated with gadodiamide dose, renal function, and time between gadodiamide administration and phlebotomy.


RESULTS
Following 42 gadodiamide-enhanced examinations, serum calcium measurements spuriously decreased by more than 2 mg/dL (0.5 mmol/L), resulting in laboratory reports of "critical" hypocalcemia (ie, calcium level < 6 mg/dL [1.5 mmol/L]) in 25 examinations. These reduced calcium measurements were correlated with serum creatinine level (r = 0.39, P <.001), gadodiamide dose (r = 0.37, P <.001), and time between gadodiamide injection and phlebotomy (r = -0.28, P <.001). Spurious reductions in calcium measurements after administration of 0.1 mmol of gadodiamide per kilogram of body weight were greater in patients with renal insufficiency (0.6 mg/dL [0.15 mmol/L] +/- 0.5 [0.125, SD]) than in those with normal renal function (0.14 mg/dL [0.035 mmol/L] +/- 0.4 [0.1]) (P <.001). After administration of more than 0.2 mmol/kg of gadodiamide, spurious calcium measurement decreases were greater in patients with renal insufficiency (2.4 mg/dL [0.6 mmol/L] +/- 3.6 [0.9]) than in those with normal renal function (0.4 mg/dL [0.1 mmol/L] +/- 0.7 [0.175]) (P <.001). Patients with renal insufficiency had spuriously low calcium measurements up to 4(1/2) days after gadodiamide administration. Seven patients were inappropriately treated with intravenous calcium and eleven with oral calcium in response to false-positive laboratory reports of critical hypocalcemia. No patient had characteristic symptoms of hypocalcemia or injuries attributed to the inappropriate medical treatment.


CONCLUSIONS
Gadodiamide administration causes spurious hypocalcemia, particularly at doses of 0.2 mmol/kg or higher and in patients with renal insufficiency.
Prince
Martin R
MR
Department of Radiology, Weill Medical College of Cornell University, 416 E 55th St, New York, NY 10021, USA. map2008@med.cornell.edu
Erel
Hale E
HE
Lent
Richard W
RW
Blumenfeld
Jon
J
Kent
K Craig
KC
Bush
Harry L
HL
Wang
Yi
Y
D002118:Calcium / Q000097:blood*; D003287:Contrast Media / Q000009:adverse effects*; D003404:Creatinine / Q000097:blood; D005260:Female; D005682:Gadolinium / Q000493:pharmacokinetics; D019786:Gadolinium DTPA / Q000009:adverse effects*; D006801:Humans; D006996:Hypocalcemia / Q000175:diagnosis*; D007275:Injections, Intravenous; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D051437:Renal Insufficiency / Q000097:blood; D012189:Retrospective Studies
D003287:Contrast Media; C064925:gadodiamide; D005682:Gadolinium; D003404:Creatinine; D019786:Gadolinium DTPA; D002118:Calcium