A rapid test for bacterial endotoxin quantification in 2-(18F)fluoro-2-deoxy-D-glucose by the kinetic chromogenic method

Full text: The Bacterial Endotoxin (BET) assay of 2-(18F)fluoro-2-deoxy-D-glucose ((18F)FDG), if done prior to release, must be very quick to minimise radioactive decay of (18F)FDG and its specific activity per mL. In order to satisfy harmonized US Pharmacopoeia BET and the FDA guidelines for LAL testing, a quantitative Kinetic Chromogenic test in an automated Portable Test System (PTS) has been developed and patented by Endosafe Inc., USA, to determine BET in ((18F)FDG). The PTS is a handheld fixed wavelength spectrophotometer that utilizes disposable cartridges for accurate and fast BET testing. It also has inbuilt facility of incubation at 37 deg C. Here, we present the data of BET analysis done using automated PTS for 15 batches of (18F)FDG produced at our Medical Cyclotron Facility. Materials and Methods: BET test was carried out by using PTS and polystyrene cartridges containing dry LAL reagents, control standard endotoxin and synthetic chromogenic substrate. The PTS had a sensitivity of 0.05EUmL-1 which is equivalent to the sensitivity of the commonly used Gel Clot assay for BET test. The assay was performed at three different MVD (Maximum Valid Dilution) i.e 1:100, 1:200 and 1:500. It was observed that higher MVD (1:500) for (18F)FDG could be used in this method as compare to used in Gel Clot method (MVD is 1:200 for (18F)FDG). Further, the sensitivity of the lysate used in this method is also high (0.05EUml-1) as compared to Gel Clot method (0.125EUml-1). Samples were also tested at a dilution (less than the MVD) in order to show the consistent elimination of the interfering factors such as pH, ionic strength and high background endotoxin. Results and Discussion: For all three different MVDs, the profile for the % Recovery Positive Product Control (RPPC) and dilution graph factor were similar in all the 15 batches of (18F)FDG. For all the batches analyzed, RPPC which represents the spike recovery, was found to be in the range of 75-150%. The coefficient variant for all the negative control sample was found to be below measurable levels and for positive control was observed to be less than 10%. BET concentrations for all the 15 batches were below the specified limit described in pharmacopoeias. Thus, kinetic chromogenic method using PTS is a rapid, simple and accurate method for quantifying bacterial endotoxin in short lived (18F)FDG and can be introduced in routine biological quality control analysis of samples before release of the product