Clinical Study to Improve the Quality of Care in Critically Ill Patients With Suspected Sepsis Through Early Molecular Diagnosis .

Background Sepsis has recently been redefined (Sepsis 3) as an infection leading to organ dysfunction (1). Although this definition is not generally accepted by all researchers (2,3) due to the potential for delayed diagnosis, mortality related to this entity could be significantly reduced by early adoption of diagnostic protocols and appropriate and early use of antimicrobial therapy (ATB).

A recent study in Catalonia (4) showed an incidence of 212 cases of sepsis per 100,000 inhabitants/year with a hospital mortality of 21%, which is significantly higher if consider ICU patients (40%) or those affected by septic shock (>50%) (5,6). These data highlight the current importance of this entity and highlight the need to seek new alternatives for early and appropriate diagnosis and treatment to have a favourable impact on the high mortality rate.

Ineffective treatment of sepsis is often due to late diagnosis of sepsis, due to the inherent complication of nonspecific clinical signs. Although procalcitonin (PCT) appears to be an adequate biomarker for the diagnosis of bacterial infection (7,8), different studies show a discrimination of only around 80% (7,8) and recent international guidelines do not recommend its use (9,10,11). These same guidelines recommend the use of scores, such as SOFA (sequential organ failure assessment) and qSOFA (a simplified version) based on the presence of altered consciousness, hypotension, and tachypnoea) for early risk stratification of patients suspected of infection.

However, sepsis and non-sepsis systemic inflammatory syndromes present as clinically similar entities, and both are frequently complicated by the appearance of organ dysfunction. Therefore, the identification of sepsis remains subjective and possibly leads to overdiagnosis of sepsis and consequently a high use of ATB in patients who do not have sepsis and who do not benefit from this treatment (12).

The availability of new molecular techniques and the automation of these laboratory analyses have stimulated the search for biomarkers related to the host response to sepsis. Analysis of host gene expression through RNA transcripts (transcriptomics) offers an opportunity in this complex setting of the critically ill patient. Host gene expression differs greatly between septic patients and healthy individuals (13). However, although gene expression between septic and non-septic inflamed patients overlaps to a large extent, several differences between transcripts observed in sepsis can help distinguish infection from other causes of inflammation [14]. The SeptiCyte™ LAB transcription assay was developed to diagnose infection in critically ill patients with suspected sepsis [15]. It is the first host response assay based on quantitative reverse transcriptase PCR (qRT-PCR) methods to be approved by the US Food and Drug Administration (FDA). SeptiCyte™ LAB allows the assessment of host response to infection by measuring the expression of specific genes involved in immune function and inflammatory signaling in whole blood. The first clinical performance study of SeptiCyte™ LAB analyzed 345 patients who were enrolled as part of the Molecular Diagnosis and Sepsis Risk Stratification (MARS) cohort in two ICUs in the Netherlands [15]. Patients were categorized as having sepsis based on a post-hoc medical assessment of the available clinical, radiological, and microbiological evidence [16] resulting in estimates for the AUC (0.77 to 0.99), sensitivity (79% to 100%) and specificity (33% to 91%) varied widely, depending on the prevalence of sepsis, the confidence level with respect to the reference diagnosis and whether patient registration was consecutive. As this analysis took about 6 hours, an early sepsis diagnostic tool (SeptiCyte RAPID (17) has been developed that is based on the measurement of two of the four gene expression biomarkers in peripheral blood (PLAC8 and PLA2G7) using the same quantitative reverse transcription polymerase chain reaction (RT-qPCR) and correlates closely with the clinical results of SeptiCyte LAB, but with a much simpler workflow. Based on the results, the device issues a report with a sepsis probability scale. (see attached algorithm) This new analysis methodology, together with the usual biomarkers, can improve the early diagnosis of sepsis, differentiate between inflamed and septic patients.