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New Septic Shock Biomarker Test

Blood analysis could improve interventions in adults

Septic shock is a severe systemic infection and a major cause of death for the old and young alike. Unfortunately, researchers say testing new drug regimens to stop the infection is confounded because clinical trials include patients who are either too sick to be saved by experimental therapies or not sick enough to warrant the treatments.

In a study published in the April edition of Critical Care Medicine, researchers at Cincinnati Children’s Hospital Medical Center and the University of Cincinnati report a new blood test that helps solve the problem by identifying low-risk and high-risk patients. Based on genome-wide studies of septic shock patients, the tool measures five protein biomarkers in the blood that are combined to accurately estimate the risk of mortality and to determine which patients should receive an experimental therapeutic intervention.

The new study involved 882 adult patients in intensive care units in the U.S., Canada, and Finland. The study follows one published earlier this year by the same research group that developed a similar test for children. The new study included three different groups of patients to develop, test, and retest the tool.

“Substantial resources are invested in trying to find new treatments for septic shock, but the vast majority of them fail when they get to clinical trials,” explains lead investigator Hector Wong, MD. “There are many reasons for this, but a consistent one is that the baseline mortality risk varies widely in septic shock patients, which muddies the water.”

Septic shock can cause inflammation and damage to critical organs. Organ damage is a key driver of the infection’s deadly nature. The authors say a significant part of the challenge in determining who is at greatest risk of death is the complex medical variation among patients with septic shock — who differ in age, underlying medical conditions, and general overall health.

Researchers selected the biomarkers used in the stratification tool because of the clear links they have to a person’s infection and inflammation. As well as biomarkers, the researchers included measurements of the patient’s age, lactate levels, and the number of chronic diseases patients had. They then used a mathematical model to combine the information into a single tool that separates high- and low-risk patients.

The authors report that, in general, the tool accurately determined that patients who tested positive had less than a 50% chance of surviving, but patients who tested negative had more than a 90% chance of surviving. More detailed analyses allowed the authors to identify patients with a more than 98% chance of surviving and those with a more than 75% chance of dying.

When the researchers tested the tool repeatedly in different groups of patients, it continued to perform well. It also performed better than what is currently available, the APACHE (Acute Physiology and Chronic Health Evaluation) II/III testing. The authors say this is because APACHE II/III does not use blood tests and relies more heavily on measurements with considerable variation, such as blood pressure.

One important finding is that three of the biomarkers helpful in stratifying the risk for adults were the same as those used for stratifying children. The researchers say having the same three biomarkers verified in both groups means that, in addition to identifying those patients unlikely to survive, the biomarkers consistently point to the same underlying problems caused by sepsis, providing potential targets for treatment. Not only can the tool help identify which patients should be included in clinical trials, it also points to specific treatments that should be tested.

Source: Cincinnati Children’s Hospital; March 26, 2014.

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