False Positive in [ 99m Tc]Tc-DPD Scintigraphy for Cardiac Amyloidosis Due to Intravenous Iron Administration.

[ 99m Tc]Tc-DPD (3,3-diphosphono-1,2-propanodicarboxylic acid) scintigraphy is an essential tool for diagnosing transthyretin amyloid cardiac amyloidosis. An 86-year-old woman suffering from heart failure with preserved ejection fraction underwent [ 99m Tc]Tc-DPD scintigraphy and a SPECT/CT for suspected transthyretin amyloid cardiac amyloidosis. The scan showed intracardiac and liver uptake. As the patient had taken intravenous iron on the morning of the scan, we decided to repeat the scan, but this time, it showed no uptake in the heart or the liver. Accordingly, we concluded the first result was a false positive due to drug interaction.