Background: The bacterial endotoxin test (BET) performed using gel clot method is a 60-min test and typically performed after the decay of the 2-((18)F) fluoro-2-deoxy-d-glucose (F18-FDG) sample to determine the endotoxin content. The objective of this study protocol was to perform BET testing of F18-FDG by gel clot method.
Materials and methods: Ten random decayed samples of the F18-FDG were subjected to the gel clot BET. The assay was performed with undiluted F18-FDG and at four different maximum valid dilutions of 1:10, 1:100, 1:350 and 1:700 (total number of tests = 100). The sensitivity of the LAL reagent used was 0.125 EU/ml. Endotoxin dilutions were freshly prepared from control standard endotoxin (CSE) stock solution for each F18-FDG batch testing. If the gel had formed and remained intact in the bottom of the reaction tube after an inversion of 180°, the test was considered positive. Any other state of the reaction mixture constituted a negative test.
Results: In the undiluted samples, the measured pH (7.05) was well within the acceptable range (i.e. 6.0-8.0) for the gel clot assay. Of the 10 undiluted F18-FDG batches and all the diluted samples, none gelled after 60-min incubation period at 37°C. However, the undiluted F18-FDG did inhibit gel formation at the lysate sensitivity of 0.125 EU/ml.
Conclusion: The total volume of FDG produced was 16 ml in the synthesis module. The total F18-FDG preparation at any time did not contain more than 8 EU (0.5 EU/ml × 16 ml). Thus, the product is safe for human administration.
Keywords: Bacterial endotoxin test; fluorodeoxyglucose; gel clot assay.