New diagnostic test for lupus

Scientists have developed a new diagnostic test for lupus, a disorder in which the immune system attacks the body. Many people with lupus have arthritis as one of their symptoms, which range from skin rash and mild fatigue to organ failure, making diagnosis difficult.

While the majority of lupus patients produce antibodies to their own tissue that can be detected with a blood test that’s been available since the 1950s, about 20 percent of patients – those who do not make such antibodies — often go undiagnosed.

A test developed by Mark Roth, Ph.D., a member of The Fred Hutchinson Cancer Research Center Basic Sciences Division, promises to bridge that diagnostic gap.

In the August issue of Arthritis and Rheumatism, Roth and colleagues report the discovery that molecules called SR proteins are particularly useful biomarkers for lupus because the majority of patients produce antibodies to them.

This discovery has spawned the development of a color-coded test to detect the presence of telltale SR proteins in the serum, the clear fluid portion of the blood. The test involves adding sera to tiny wells in a plastic plate that has been coated with human SR proteins. Antibodies in the sera that stick to the SR proteins are detected by a colored molecular tag; sera from lupus patients turns purple, while sera from non-affected individuals remains clear. This test can identify 50 percent to 70 percent of lupus patients who react positively to SR proteins.

The Hutchinson Center has filed for patent protection on this assay system and expects great commercial interest in the technology, now available for license from the Center.

“This is an exciting and novel development,” says J. Lee Nelson, M.D., a clinical research investigator at the Hutchinson Center who studies the pathology of autoimmune diseases.

The technique arose from a scientific experiment more than a decade ago, when Roth and colleagues injected mice with extracts of frog nuclei. Antibodies produced by these mice led to the discovery of the SR proteins used in this new screening test.

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