A novel multiplex quantitative polymerase chain reaction assay for the early prediction of sepsis in critically ill patients presenting signs of shock and organ dysfunction

Background

Clinical signs of sepsis often overlap with other symptoms present in patients after trauma, surgery and chemotherapy, amongst others. The clinical utility of existing biomarkers to detect sepsis, such as procalcitonin (PCT) and C-reactive protein (CRP), is limited in patients suffering from shock and organ dysfunction. As a result, tests with superior positive and negative predictive values are mandatory in life-threatening infection.

Methods

We have analyzed the clinical utility of a new class of transcriptomic biomarkers derived from circulating leukocytes. Prospectively collected whole blood samples from 460 patients admitted to the operative ICU of the University Hospital Jena were used in a microarray/quantitative PCR study to identify sensitive and specific biomarkers. Microarrays comprising 5,308 probes corresponding to 3,704 human genes relevant to inflammation, immune response and related processes were used for analysis. The identification of a signature specific for the discrimination between systemic inflammatory response syndrome and sepsis in patients suffering from shock and organ dysfunction was performed in independent training and test phases. The training set of 96 patients was selected by an independent ICU committee. An algorithm was established combining and transforming the gene-expression signals into a continuous, nondimensional score indicating either infectious or noninfectious causes for organ dysfunction. The resulting classificator was validated in a test set comprising 1,784 ICU days of 364 patients. For each marker, a robust quantitative PCR assay was established.

Results

The final microarray signature could be transferred into a multiplex quantitative PCR format retaining full sensitivity and specificity with a time to result of approximately 5 hours. Moreover, it could be demonstrated that the combination of seven biomarkers possesses the same accuracy compared with the complete biomarker set. The area under the curve in the test group was determined as 0.79 (PCT – 0.65, CRP – 0.67). Moreover, the quantitative PCR assay determined the onset of sepsis up to 48 hours prior to the clinical diagnosis backed by daily CRP and PCT testing.

Conclusion

With its high predictive value for the differentiation between infectious and noninfectious causes of shock and organ dysfunction, this new class of biomarkers may help to identify patients with life-threatening infections among patients at risk and to guide therapy (for example, with anti-infective agents).