Rates of agreement of endotoxin, procalcitonin and lactate in septic and non-septic critically ill patients

Introduction

In contrast with many acute and severe diseases such as myocardial infarction, liver failure and renal failure, severe sepsis lacks a specific biomarker. A useful marker of severe sepsis will guide therapy by identifying which patients have the pathological process of interest.

Objective

To compare the rates of agreement between PCT and lactate (LAC) assays with endotoxin levels in severely septic and non-septic critically ill patients.

Methods

Data were collected from stored frozen plasma samples from a multicenter study evaluating the Endotoxin Activity (EAA) Assay [1]. We evaluated test samples based on the presence of clinical determination of severe sepsis where n = 17 had elevated EAA levels and n = 7 had low EAA levels. There were n = 18 from non-septic critically ill patients with low EAA values. We then performed PCT and lactate assays on the same samples by technicians who were blinded to EAA results and clinical diagnosis. Overall percent agreement (weighted kappa statistic): EAA vs PCT = 73.81% (0.462), EAA vs lactate = 40.5% (-0.247), lactate vs PCT = 42.9% (-0.183) The EAA correctly identified 17 of 24 severely septic patients, thus showing a positive agreement of 70.8%. The PCT and lactate assays correctly identified 15 and six patients, respectively. The positive agreement with the consensus definition of severe sepsis was 62.5% for PCT and 25% for lactate.

Conclusions

Both PCT and endotoxin are elevated in patients with severe sepsis. The reported positive agreement with a clinical diagnosis of severe sepsis provides evidence of their value as a diagnostic marker. The poor positive agreement between lactate levels and the presence of severe sepsis suggests this marker may have other value such as for prognosis. Further study is required to evaluate each of these markers as a measure of response to therapy.

Table 1 Table 1