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Comparison of standard test for bacterial endotoxin detection with a rapid slide method

Abstract number: P1403

Christensen M., Hoegh M., Rubenhagen B., Andersen L.

Objectives: Testing surveillance and environmental samples for endotoxin content with the standard test procedure (The LAL endochrome test from Charles River Laboratories) performed at Rigshospitalet is often laborious. Furthermore the extend of pipetting work may in the long run cause arthritis like conditions in the fingers of the technicians working with the LAL method.

Charles River Laboratories has developed a revolutionary FDA-licensed endotoxin detection system, the Endosafe PTS, which is a portable and handheld rapid point-of-use test system comprising a simple one-button operation. Both the LAL test and the Endosafe PTS method are based on a kinetic chromogenic methodology.

This study compares the LAL method with the new PTS method.

Methods: A total of 18 tests are performed with the LAL method and the PTS method.

The first step is to dilute an E. coli control standard Endotoxin manually, thereby creating a standard dilution row. The 18 tests are separated into 3 standard rows each comprising 6 concentrations (0; 0.05; 0.12; 0.25; 0.50; 1.00 EU/ml). From this point the 18 dilutions are subjected to the LAL procedure first (lasting about 1.5 h) and to the PTS method in the meantime. The PTS method involves an application of 25 ml of sample to 4 wells on a slide, which is then inserted into the PTS apparatus and the endotoxin measurement is completed within a maximum of 15 minutes. Thus the PTS system requires a minimum of hands-on time.

The measured concentrations of the dilutions in both the LAL and the PTS method are based on optical densities.

Results: The results are viewed in table 1, which shows the endotoxin concentration measurements from the LAL method and the PTS method.

Conclusion: When making a graph, based on the values in table 1, it is clearly seen that the tendency with the LAL method is that the values are unevenly increasing until the 0.50 point and then the curve decreases. However the measurements in the PTS method are following a straight line increasing approximately two-fold, which agrees with the manually produced dilution rows. Thus a conclusion must be that the standard method produces uncertain results, most likely caused by an error in the reader device, and that the PTS system conducts more reliable, all though systematically low, measurements.

Table 1: Endotoxin measurements from LAL method and from PTS method

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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