Clinical and economic impact of falsely decreased calcium values caused by gadoversetamide interference.
OBJECTIVE
Gadolinium is administered as a contrast agent in MRI procedures. Two gadolinium-based contrast agents, gadodiamide and gadoversetamide, interfere with colorimetric total serum calcium methods. The purpose of this prospective observational study was to examine the incidence of calcium interference after gadoversetamide procedures, associated clinical outcomes, and costs 20 months after implementation of quality assurance and physician education programs.


METHODS
Records of patients who received gadoversetamide from June 24, 2006, to October 7, 2006, were reviewed to determine if a routine calcium test had been performed after the injection. Calcium values were repeated with an alternate method that is less susceptible to gadoversetamide interference. If the difference was > or = 2.0 mg/dL or if the initial test value was < or = 7.0 mg/dL, patient charts were reviewed for any related treatment. Costs associated with this algorithm were tracked.


RESULTS
The initial calcium test was performed after gadoversetamide in 766 of 3,439 instances. The alternate test was performed in 633 of 766. One hundred twenty-five of 633 (20%) showed a difference in calcium values that was > or = 0.7 mg/dL, with 16 showing differences of > or = 1.6 mg/dL. Chart review for 56 instances revealed that calcium supplements were administered in 22 of 56 around the time of gadoversetamide injection. However, none appeared to be related to the spurious hypocalcemia. The total additional cost (reagent and technologist) for following this algorithm for just over 3 months was $6,807.


CONCLUSIONS
Approximately 20% of patients receiving gadoversetamide exhibited spurious hypocalcemia. No patients were identified who received inappropriate calcium because of this interference. This may be attributable to the quality assurance and physician education programs.
Gandhi
Manish J
MJ
Department of Pathology and Immunology, Washington University School of Medicine, 660 S Euclid Ave., Box 8118, St. Louis, MO 63110, USA.
Narra
Vamsidhar R
VR
Brown
Jeffrey J
JJ
Guo
Amy
A
Grosu
Daniel S
DS
Parvin
Curtis A
CA
Scott
Mitchell G
MG
D001774:Blood Chemical Analysis; D002118:Calcium / Q000097:blood*; D003124:Colorimetry; D003287:Contrast Media / Q000494:pharmacology*; D005189:False Positive Reactions; D005260:Female; D017048:Health Care Costs; D006801:Humans; D006996:Hypocalcemia / Q000175:diagnosis* / Q000191:economics* / Q000628:therapy; D008279:Magnetic Resonance Imaging; D008297:Male; D009942:Organometallic Compounds / Q000494:pharmacology*; D011446:Prospective Studies; D012189:Retrospective Studies
D003287:Contrast Media; D009942:Organometallic Compounds; C112666:gadoversetamide; D002118:Calcium