A comparative study of Endosafe® PTS system and standard assay methods for Endotoxin Test of [¹⁸F]FDG, [¹¹C]PiB and [¹³N]NH

Objectives The pyrogen test represents an important parameter for QC of PET tracers [1]. However, the standard test proposed by the U.S. Pharmacopeia using limulus amebocyte lysates takes too long (about 1 h) [2] for short-lived PET tracers. Recently, a rapid test method, Endosafe^® Portable Test System (PTS), has been approved by FDA and was claimed that it took only approximately 15 min to complete the test. The aims of this study were to evaluate PTS^TM performance for PET tracers and head-to-head comparison with other traditional Limulus amebocyte lysate (LAL) systems.

Methods PTS as well as traditional assay methods, Lonza kinetic chromogenic (KCA) and Endosafe^® kinetic turbidimetric (KTA) assay systems were performed on 3 consecutive batches of on-site produced [¹⁸F]FDG, [¹¹C]PiB and [¹³N]NH₃ with 6 different executors (Fig. 1). The sensitivity of cartridges used for all samples tested with the PTS was 0.05-5.0 EU/mL. Additionally, fabricated endotoxin-positive samples containing a fixed concentration of endotoxin (RSE) were prepared and used as controls.

Results The results of Endotoxin detection among these tripled methods were similar in most cases. However, the storage condition of endotoxin standards in KCA measurement has significant impact on the results of the Endotoxin detection and the KCA measurement is the most time-consuming method among these three methods ( the time of PTS, KCA and KTA were 16±1, 48±5 and 27± 1 min, respectively (n=9)).

Conclusions The Endosafe® PTS provides reliable results for Endotoxin test and is the most suitable method for short-lived PET radiotracers.