Researchers identify biomarkers that could lead to more accurate diagnosis of systemic lupus erythematosus

University of Pittsburgh researchers have identified biomarkers that could result in earlier and more accurate diagnosis of systemic lupus erythematosus (SLE), a devastating disease that affects as many as 1.5 million Americans, and occurs 10 to 15 times more frequently in women.

The results are published in the November 2004 issue of Arthritis & Rheumatism.

"This is the first report of abnormal levels of the protein erythrocyte-C4d in human disease," said lead author Susan Manzi, M.D., M.P.H., associate professor of medicine, epidemiology and dermatology at the University of Pittsburgh School of Medicine and the University of Pittsburgh Graduate School of Public Health. "Abnormally high levels of erythrocyte-C4d and low levels of erythrocyte-CR1 are characteristic of SLE and combined measurement of the two proteins has high diagnostic sensitivity and specificity for lupus."

The significance of the finding is substantial, according to Joseph Ahearn, M.D., associate professor of medicine at the University of Pittsburgh School of Medicine and senior author of the study.

"Today we are one step closer to providing patients with an immediate and accurate diagnosis, one step closer to providing physicians with the ability to offer better treatment options and one step closer to providing incentive to lower the cost of health care for patients suffering from lupus," Dr. Ahearn said.

"Lupus is the prototypical autoimmune disease and arguably the greatest diagnostic challenge among rheumatologic diseases," he said. "The spectrum of disease among patients with SLE is broad and ranges from subtle or vague symptoms to life-threatening multiorgan failure, and the manifestations of lupus often mimic those of other diseases makes it difficult to diagnose."

It is not unusual for a patient with lupus to seek advice from a variety of specialists and subspecialists over a period of years before being accurately diagnosed, which results in delays in receiving proper therapy and an ultimately greater cost for treating the disease and its complications. Although there is no cure for lupus, there are many ways to treat symptoms, including chemotherapy.

Currently, most physicians rely on blood abnormalities to aid in the diagnosis of SLE, but according to Dr. Manzi, these tests are inadequate because they are not sensitive or specific enough.

In the study, researchers used blood samples taken from each participant and analyzed them using flow cytometry to compare the levels of proteins in 100 patients who were confirmed to have lupus, 133 patients who had other diseases and conditions including myositis, systemic sclerosis, hepatitis and rheumatoid arthritis, and 84 healthy patients.

Lupus is a widespread and chronic autoimmune disease that, for unknown reasons, causes the immune system to attack the body's own tissue and organs, including the joints, kidneys, heart, lungs, brain, blood and skin.

The immune system normally protects the body against viruses, bacteria and other foreign materials. In an autoimmune disease like lupus, the immune system loses its ability to tell the difference between foreign substances and its own cells and tissue. The immune system then makes antibodies directed against itself.