Newly developed endotoxin measurement method (endotoxin activity assay) may reflect the severity of sepsis

Introduction

Endotoxin (ET) is a structural molecule of the Gram-negative bacilli extracellular membrane, which activates target cells including macrophages and neutrophils, and causes septic shock. But it is known that the conventional ET measurement method has many problems; for example, a discrepancy between plasma ET concentration and clinical manifestation in the septic patient. We therefore evaluate the usefulness of a new developed method to measure the plasma ET activity (endotoxin activity assay (EAA)) [1] in patients under sepsis compared with the ordinary method of the limulus amebocyte lysate (LAL) assay.

Methods

With institutional approval and informed consent, we measured the EAA in 40 patients (aged 63.5 ± 17.7 years) admitted to the ICU. The EAA was measured using a chemiluminometer (Autolumat LB953; EG & G. Berthold). Patients were divided to five categories: (1) control group, (2) systemic inflammatory response syndrome (SIRS) group, (3) sepsis (SIRS and infection) group, (4) severe sepsis group, and (5) septic shock group. We then compared the EAA level between each group and control group. We made the statistical evaluation by unpaired t test and a significant difference was P < 0.05.

Results

The EAA levels were significantly increased as sepsis severity rises. The measured EAA levels were (0.18 ± 0.09), (0.33 ± 0.19), (0.39 ± 0.16), (0.65 ± 0.25) and (0.78 ± 0.34) in control, SIRS, sepsis, severe sepsis and septic shock groups, respectively. In the LAL method, four of the severe sepsis group and two of the septic shock group exceeded the cutoff value. In the EAA level, severe patients had a tendency to exceed the cutoff value. There was no significant correlation between the EAA level and ET density.

Conclusion

This newly developed method named EAA measures ET using anti-lipopolysaccharide monoclonal antibody. Our trial suggests this method can evaluate the severity of sepsis correctly compared with the usual method of measuring ET.