Chocolate intake associated with failed labeling of (99m)Tc red blood cells.

UNLABELLED Red blood cells (RBC) labeled in vivo with (99m)Tc-pertechnetate are used worldwide in nuclear medicine departments. METHODS Here, we present a case of (99m)Tc-RBC labeling failure associated with chocolate intake in a 25-y-old woman, resulting in uninterpretable images. Because of this clinical observation, we performed in vitro RBC labeling on blood samples from volunteers after they consumed chocolate. RESULTS Chocolate intake inhibited the labeling rate, compared with the control condition, and significantly increased the (99m)Tc free fraction (34.1% +/- 11.3% vs. 14.0% +/- 1.2%). CONCLUSION We cannot explain how this interaction could occur, but cacao components are known to modulate red cell and plasma oxidoreductive status and to modify red cell membrane permeability and plasticity. Therefore, for patients who can be considered likely to consume chocolate, such as young patients, we recommend that they limit their consumption of chocolate for 12 h before RBC labeling.