NANOCIS®: Possible errors in the summary of product characteristics quality control method and a suggested...

Determination of the radiochemical purity of [^99mTc]NANOCIS® was performed using the procedure described in the Summary of Product Characteristics (SPC). In contrast to the clinical findings of thyroid gland accumulation indicating free [^99mTc] pertechnetate, the QC results showed no free [^99mTc]pertechnetate. This discrepancy prompted us to further investigate the described QC procedure. The aim of our study is to develop a correct QC procedure for [^99mTc]NANOCIS®.

After ^99mTc-labelling performed in accordance with the SPC, QC was performed on two stationary phases (Whatman No. 1 and ITLC-SA) with both wet and dry application spots.

All QC samples prepared using the method described in the SPC (Whatman No. 1 with dry application spot) indicated an acceptable labelling with a radiochemical purity over 99 %. The QC methods performed using non-SPC described methods (Whatman No. 1 with wet application spot, ITLC-SA with wet and dry application spot), show more impurities, resulting in radiochemical purity ranging between 68 % and 99 %. All results from the three QC procedures not outlined in the SPC resulted in comparable results. When comparing the QC results with imaging of the thyroid gland, if the correct TLC method is used, a clear connection was observed between low radiochemical purity, as a result of free [^99mTc]pertechnetate present in the prepared radiopharmaceutical, and visualisation of the thyroid gland, due to thyroid uptake of the free [^99mTc]pertechnetate.

Drying the application spot on Whatman No. 1 paper indicates erroneous high labelling. To obtain a correct QC result, either an analytical method using Whatman No. 1 papers without drying of the application spot or a method using instant thin layer chromatography with a silica acid coating (ITLC-SA) should be used.