Diagnosing sepsis from a drop of blood

When a body displays an extreme reaction to an infection it could be caused by sepsis. In some cases the reaction is so severe that it can cause organ failure and death. A new diagnostic tool, however, may be able to quickly identify sepsis biomarkers from less than a pinprick of blood.

According to the World Health Organization (WHO), each year, sepsis affects over 30 million people around the world. Sepsis may also lead to around 6 million deaths each year. To prevent sepsis from evolving into septic shock — a complication that makes premature death more likely — doctors have to diagnose it early and act on it quickly.

Yet current diagnostic methods are often symptomatic, combined with tests checking for general markers of infection or organ damage. Moreover, many of the signs and symptoms of sepsis, such as fever and difficulty breathing, are the same as in other conditions, making sepsis hard to diagnose in its early stages.

Researchers have been looking for quicker, more effective ways of diagnosing sepsis, including devices that detect the presence of biomarkers for sepsis in a person’s blood. A top biomarker for this condition is interleukin-6 (IL-6), a protein the body produces when inflammation occurs, and levels of which tend to increase in the blood before other symptoms of sepsis sets in.

Though detecting IL-6 is identified as a good way to diagnose sepsis, the blood concentration of IL-6 remains too low for existing tests to pick up on it. Now, researchers at the Massachusetts Institute of Technology (MIT) in Cambridge have developed a device that is sensitive enough to identify the presence of a biomarker for sepsis from a tiny amount of blood.

The new diagnostic tool is a microfluidics device that is able to detect key biomarkers in extremely small amounts of body fluid. This particular device uses microbeads ‘coated’ with antibodies.
When a blood sample is introduced into the device using a pipette, the antibodies latch onto the IL-6. Then, another part of the device uses an electrode and the beads that have captured IL-6, emit an electric signal for each IL-6 bead that passes through. This allows researchers to identify at what concentration the protein is present in the blood sample.

The entire process only takes about 25 minutes, and the device uses only about 5 microliters of blood — that is, around 25 percent of the total volume of a blood drop drawn through a finger prick. Also, the new tool is able to detect extremely low concentrations of IL-6 — as low as 16 picograms per milliliter, which is lower than the biomarker concentration that indicates the presence of sepsis.

This suggests that the device is very sensitive to the presence of key biomarkers. More importantly, the scientists argue that the innovative tool is highly adaptable and could be set to detect other sepsis biomarkers as well, and, in future, could be adapted to screen for biomarkers of other conditions, too.