A Possible New Test for Diagnosing Sepsis

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The summary below is from the full report titled "Plasma Level of a Triggering Receptor Expressed on Myeloid Cells-1: Its Diagnostic Accuracy in Patients with Suspected Sepsis." It is in the 6 July 2004 issue of Annals of Internal Medicine (volume 141, pages 9-15). The authors are S. Gibot, M.-N. Kolopp-Sarda, M.C. Béné, A. Cravoisy, B. Levy, G.C. Faure, and P.-E. Bollaert.

What is the problem and what is known about it so far?

Bacterial infection of the blood can result in a condition called sepsis, the most common cause of death in intensive care units. This type of infection can lead the body to make chemicals that cause a severe form of inflammation, called the systemic inflammatory response syndrome (SIRS). This syndrome occurs in patients with sepsis and in sick people who do not have sepsis. Telling the difference between SIRS with sepsis and SIRS with no sepsis is important because patients with sepsis need immediate treatment with antibiotics. It can be very difficult to know if a patient with SIRS also has sepsis, so a test for sepsis would be helpful. Doctors do test for bacteria in the blood, but this test can take many hours to become positive. The ideal test would give an answer right away, so that doctors could decide whether to use antibiotics and be fairly sure they made the right decision. Doctors usually start antibiotics immediately when they suspect sepsis, so many patients who don't have sepsis get antibiotics for several days until results of blood tests for bacteria are negative. Exposure to antibiotics can be harmful.

One possibility is to detect a protein made by inflammatory cells that kill bacteria. When bacteria are present, inflammatory cells rapidly start making a protein that causes inflammation. This protein, called triggering receptor expressed on myeloid cells-1 (TREM-1), is present on the surface of the inflammatory cells. As these cells circulate in the blood, some of the TREM-1 gets into the blood. Blood levels of TREM-1 are high during bacterial infection and low in other causes of SIRS.

Why did the researchers do this particular study?

To determine whether the blood level of TREM-1 was a good test for sepsis in patients with SIRS.

Who was studied?

76 patients who were admitted to intensive care units because their doctors thought they might have infections of the blood.

What did the researchers do?

The researchers took a careful history, performed tests to measure the severity of illness, and drew blood to test for TREM-1 and for bacteria in the blood. Two expert physicians reviewed all of the information (except blood TREM-1 levels) and diagnosed SIRS (without bacterial infection of the blood) in 29 patients, bacterial infection of the blood in 22 patients, and bacterial blood infection with shock (the most severe form of bacterial blood infection) in 25 patients.

What did the researchers find?

A blood TREM-1 level above a certain value was a very good test for bacterial infection of the blood. It detected almost all the patients with sepsis (96%). Only 11% of patients with SIRS but not sepsis had increased TREM-1 levels. This means that a doctor would be correct 97% of the time if she said that a patient with an increased TREM-1 level had sepsis.

What were the limitations of the study?

Since the patients were all quite sick, it is not possible to say how the test would work in less ill patients. The authors also did not study patients older than 80 years of age or patients who had weak immunity.

What are the implications of the study?

The test for TREM-1 may help doctors to correctly diagnose sepsis much more quickly, which means that they can avoid giving antibiotics to people who don't have sepsis.