005-50 EU/mL in the KQCL and 0.01-100 EU/mL in the turbidimetric methods). Because the levels of endotoxin found in endodontic infection 8, 14 and 15 are above the endpoint-QCL sensitivity (1 EU/mL), a higher serial dilution is required for such a method, particularly in symptomatic teeth (11). Nevertheless, when considering the dilution method, not only the concentration of endotoxin is diluted but the test sensitivity

is also affected. According to the endodontic literature, the present investigation has shown that all three LAL methods tested were sensitive enough for the investigation of endotoxin in primary endodontic infection because endotoxin was detected in 100% of the root canal samples 9, 11, 13, 14 and 15. The KQCL BMS-387032 mouse test yielded a median value of endotoxin close to and not significantly different from that of

the turbidimetric kinetic test (7.49 vs 9.19 EU/mL, respectively). The differences in endotoxin measurement between these two kinetic methods might be related not only to the test principle itself (use of a chromogenic synthetic LAL substrate in the KQCL vs a native substrate [coagulogen] in the turbidimetric method) but also to unique assay variations, such as the time for adding reagent to multiple wells and the inability to control the incubation temperature in the microplate readers. These are important factors toward interassay comparisons 18, 30 and 31. Under these conditions, the interassay coefficients of variation between these two kinetic tests were lower than 25% as expected (18). In contrast to the LBH589 mw kinetic tests, the endpoint-QCL method

showed a median value of endotoxin approximately five times greater than that of both kinetic methods (34.2 EU/mL), suggesting an interference with the LAL substrate by Vorinostat the samples. Such interference with the endpoint QCL was confirmed by the inhibition/enhancement assay (spiked values lower than 0.4 EU/mL ± 25%), even after serial dilutions of the clinical samples (up to 10−4). Endodontic investigations 11 and 14 using the endpoint-QCL test also reported higher levels of endotoxin. It is worth pointing out that although kinetic QCL uses a single reagent, the endpoint QCL has two stages: LAL activation followed by the addition of a chromogenic substrate (a chromophore release stage), both critically depending on time and temperature (29). The use of a single-reagent assay seems to improve the precision, speed, and accuracy of the tests 27 and 29. Foremost, the inhibition/enhancement assay indicated a good interaction between the root canal samples and both kinetic methods (KQCL and turbidimetric) by showing most of the PPC percentage values within the acceptable range (50-200) as recommended by the US Pharmacopoeia.