SPECTRAL MEDICAL
EAA™ ENDOTOXIN ACTIVITY ASSAY
Until the EAA™, there has been no reliable method to measure endotoxin accurately in the bloodstream. It is an semi-quantitative test in the measurement of endotoxin activity (EA) and allows for rapid measurements whereby results can be obtained in approximately 30 minutes.
ENDOTOXIN AND SEPSIS
Therefore, the utility of the EAA™ as a diagnostic tool, when used in conjunction with relevant diagnostic tests and clinical information, may allow for risk assessment of patients for progression to severe sepsis based on EA measurement.
A prospective cohort study, MEDIC (Multi-Center Endotoxin Detection in Critical Illness) of 857 consecutive new patients to ICU evaluated the usefulness of EAA™ as a diagnostic tool in sepsis and septic shock. Specifically, the study was carried out in order to determine the prevalence of endotoxemia in the critically ill as well as to determine if any association exists between EAA™ values at time of admission to ICU and disease outcome. Results of the study indicate that rate of endotoxemia was quite high in critically ill patients: 26.6% of the cohort had EA levels 0.4-0.6 and 30.6% of the cohort had EA levels ≥0.6. Further analyses showed that for the 74 patients meeting the criteria for severe sepsis, EA levels at the time of ICU admission were significantly higher (0.57±0.26 vs. 0.46±26, P<0.001).
Multivariate regression analysis of the data uncovered that EA levels at time of admission had a significant association with the development of severe sepsis on day of ICU admission, either as a continuous variable (P=0.02) or as a categorical one (P=0.0001); when patients were stratified based on EA levels to low (<0.4), intermediate (0.4- 0.6) and to high (>0.6) groups, it was noted that the odds of developing severe sepsis in the first 24 hrs of ICU admission was 2.0 (95% CI) for the intermediate group and 3.0 (95% CI) for the high group. These data strongly indicated the usefulness of EAA™ as a diagnostic tool in initial risk stratification and subsequent management of septic patients.
EAA™ ENDOTOXIN ACTIVITY ASSAY
The EAA™ is a chemiluminescent bio-assay based on the oxidative burst reaction of activated neutrophils to complement coated LPS-IgM immune complexes.
The IgM antibody, a key reagent, is specific for the Lipid A portion of endotoxin (LPS). In the presence of LPS, the ensuing oxidative burst results in light emission in the presence of luminol.
EAA™
The EAA™ is a highly sensitive test for endotoxin activity with the greatest sensitivity in the lowest concentration ranges of endotoxin. The dose response curve flattens in the higher endotoxin activity ranges, with no hook effect observed.
The EAA™ is a semi-quantitative test that will provide an Endotoxin Activity (EA) result. The endotoxin activity result will stratify patients into a low (<0.40), intermediate (0.40-0.59) and high (≥0.60) endotoxin activity level, allowing for stratification of patients based on endotoxin load.
The EAA dose response is an exponential curve characterized by two asymptotes. The EAA generates a unit less number, called endotoxin activity, which correlates to the concentration of endotoxin in the sample.
HOW THE EAA™ IS DIFFERENT*
The LAL assay is a highly sensitive test for endotoxin measurement in crystalloid solutions, and is not accurate when utilized in whole blood or plasma. This is due to the fact that blood contains many components known to inhibit or activate the enzymatic cascade of the LAL, such as serine proteases. In order to attempt to use the LAL for blood based endotoxin testing, the sample must first be treated with strongly acidic or caustic chemicals, increasing the risk to the user, complexity of the test, and assay time from sample to result.
The EAA™ is a rapid assay (approximately 30 minutes from sample to result) designed specifically for endotoxin activity measurement in whole blood.
EAA™ ENDOTOXIN ACTIVITY ASSAY
How does the EAA™ detect endotoxin?
What is the difference between EAA™ and the LAL assay?
What is the sensitivity of the EAA™?
What is the specificity of the EAA™?
Where does specificity of the EAA™ for LPS come from?
What is the range of the EAA™?
What is the LLD/LOD of the EAA™?
What is the molecular form of the endotoxin that the assay detects?
In which animal species is the EAA™ known to work, in which species is it known not to work?
What specimens can be used with EAA™?
The sample specimen must be whole blood drawn via indwelling catheter or venipuncture. The sample can be stored at room temperature (18-25OC) in an EDTA anticoagulated draw tube, and must be used to run the EAA™ within 3 hours of draw.