Validation of Rapid Gel-Clot Testing for the Detection of Bacterial Endotoxin in PET Radiopharmaceuticals with the Standard Cartridge Method- An Economical Solution for Routine Endotoxin Testing

Objectives: Endotoxin testing is mandatory for radiopharmaceuticals before human administration, as per the World Health Organisation (WHO) guidelines on the use of radiopharmaceuticals in humans. Bacterial endotoxin testing (BET) is mostly performed using either the gel-clot or the chromogenic (cartridge) method. Material and Methods: In this study, we have validated the rapid gel clot method with the chromogenic (cartridge) method. We tested three radioactive [ 18F ]FDG samples (n = 3) and three decayed [ 18 F]FDG samples using both a rapid gel assay and a cartridge-based method. Different dilutions were prepared, and the samples were incubated at 37 °C for a pre-set time. Results: Both techniques yielded concordant results, and endotoxin was detected below the reference value in the radiopharmaceutical samples. Though the cartridge method was more sensitive and robust, the rapid gel technique requires accurate pipetting and handling. The rapid gel assay is user-friendly and economical for routine testing, especially in developing countries or smallscale facilities. Conclusion: The rapid gel assay can serve as an alternative for qualitatively testing endotoxin levels.