Potential antibody blood test shows accuracy in spotting sarcoidosis

Screens for 2 antigens particularly common in blood of people with this disease

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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A test that detects disease-specific antibodies in the blood could help to diagnose sarcoidosis more quickly and easily, according to a recent study.

“More testing needs to be completed before this screening method is ready for clinical use, but it’s possible that could be a reality within a few years,” Lobelia Samavati, MD, the study’s senior author and a professor of molecular medicine and genetics at Wayne State University in Detroit, said in a press release.

Samavati is also director of the university’s sarcoidosis center.

The study, “Discovery of Two Novel Immunoepitopes and Development of Peptide-based Sarcoidosis Immunoassay,” was published in the American Journal of Respiratory and Critical Care Medicine. The work was supported by the National Institutes of Health (NIH).

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Sarcoidosis is an inflammatory disorder marked by abnormal clumps of immune cells called granulomas, which can affect various organs but usually appear in the lungs. Diagnosing the disorder requires identifying these granulomas, plus additional tests to rule out other diseases.

“Currently, diagnosing sarcoidosis isn’t a straightforward process, and requires tissue removal and testing with additional screenings to rule out other diseases, such as tuberculosis or lung cancer,” said James Kiley, PhD, director of the division of lung diseases at the NIH’s National Heart, Lung, and Blood Institute. Kiley wasn’t directly involved with this study.

Although the causes of sarcoidosis aren’t fully understood, it’s thought that immune proteins called antibodies are key for starting the formation of granulomas.

Each antibody is able to bind to a specific molecular target, called an antigen. It’s thought that some specific antibodies sticking to their particular antigens might be the first step in the formation of granulomas. But what those antigens might be has been hard to identify.

Scientists at Wayne State analyzed antibodies from people with sarcoidosis and other respiratory diseases. They found that antibodies targeting two specific antigens — Cofilin micro and Chain A — were much more common in people with sarcoidosis.

Based on this finding, the researchers developed a diagnostic test. Put simply, the test involves exposing a sample of a person’s blood to both Cofilin micro and Chain A to see if that person has antibodies against these antigens.

Researchers then assessed the test’s accuracy at identifying sarcoidosis in 386 people — 186 sarcoidosis patients, 100 people with no known health problems, and 100 people with other lung diseases (specifically, tuberculosis or lung cancer).

Results showed that, based on Cofilin micro alone, the test accurately identified 97% of the people with sarcoidosis and 90% of those without this disease. Based on Chain A alone, the test accurately identified 90% and 83% of people with and without sarcoidosis, respectively. Its accuracy was even higher when the two antigens were combined.

“These results provide a novel [antibody-based test] for sarcoidosis,” the researchers concluded, suggesting that these findings could be used to develop a simple blood test to help diagnose the disorder.

“Using a blood test will help diagnose faster, particularly in those organs that are more challenging to biopsy and with less harm to the patient,” Kiley said.