Does the chocolate interfere with the radiolabelling of erythrocytes with 99 mTc?

We present in this work the case of a failure of erythrocytes labelling with 99mTc for a twenty five years old patient making the examination not interpretable. The patient reported that she drank a chocolate drink the morning before the examination. it is the first observation of a such interaction between the chocolate consumption. We do not have any explanation at this date, some compounds in the cocoa can be considered with caution. Some flavonoids (catechins and pro-cyanidins) modify the plasmatic and intra-erythrocyte oxido-reducer statute and could interact with the labelling (specific reduction of the 99mTc pertechnetate in the middle of erythrocyte by the tin pyrophosphate. These compounds, as well as the methyl-xanthine-theobromine, seem modify the membrane permeability of erythrocytes and could interfere with the input of pyrophosphate or 99mTc-pertechnetate in the middle of erythrocyte. these observations, in spite of preliminary ones, lead us to recommend near the patients to avoid the chocolate foods in the twenty four hours before this type of examinations. (N.C.)