FDA Clears New Antibody Test to Help in SLE Diagnosis

Marta Figueiredo, PhD avatar

by Marta Figueiredo, PhD |

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diagnostic test for lupus | Lupus News Today | illustration of blood in vials and syringe

Thermo Fisher Scientific has received regulatory authorization in the U.S. to market its EliA Rib-P blood test, designed to improve the diagnosis of systemic lupus erythematosus (SLE), particularly in patients without hallmark antinuclear antibodies (ANAs).

The U.S. Food and Drug Administration (FDA) cleared the new antibody test, along with a second Thermo blood test, called EliA RNA Pol III, for the diagnosis of systemic sclerosis (SSc). Also known as scleroderma, SSc is another autoimmune disease — one affecting the connective tissue that provides structure and support throughout the body.

Both tests work by detecting autoantibodies — antibodies that wrongly recognize the body’s own proteins as foreign, mounting immune attacks against them. In SLE, the test identifies anti-ribosomal P (Rib-P) autoantibodies, while in SSc, it detects anti-RNA Polymerase III (RNA Pol III) autoantibodies.

“Autoimmune diseases can be a challenge to diagnose,” Henry Homburger, MD, laboratory director of Thermo Fisher’s Phadia Immunology Reference Laboratory, in Michigan, said in a press release.

“Reliable and accurate laboratory tests that provide clinical clarity are essential tools for clinicians managing these patients,” said Homburger, also a professor emeritus of laboratory medicine at the Mayo Clinic College of Medicine, in Minnesota.

Having both a new lupus and scleroderma diagnostic test will help differentiate these disorders from other connective tissue diseases (CTD), according to Homburger.

“The addition of RNA Polymerase III and Ribosomal P to the EliA connective tissue disease test menu will add considerable value to the diagnosis of SSc and SLE,” he said.

Homburger also noted that “targeting existing diagnostic care gaps can potentially lead to earlier and more accurate diagnosis and ultimately improve clinical outcomes for patients.”

“The availability of a strong CTD test menu on a fully automated instrument could improve the efficiency and productivity of diagnostic laboratories,” he added.

In autoimmune diseases, the immune system wrongly produces autoantibodies that target specific proteins and ultimately cause damage.

Most people with lupus have ANAs, or antibodies against molecules found in the cell’s nucleus, where all genetic information is stored. The most common ANAs are those against double-stranded DNA (anti-dsDNA) and the Smith protein (anti-Sm). The presence of ANAs is part of the American College of Rheumatology classification criteria for SLE.

Anti-Rib-P autoantibodies, which target the ribosomal P protein, are highly specific for SLE and detected in about 10–47% of lupus patients. These autoantibodies have been linked to younger age at disease onset and an overall severe disease course, including the presence of neuropsychiatric episodes, kidney disease, and liver disorders.

While they are not currently part of SLE classification criteria, anti-Rib-P autoantibodies have been suggested as an additional SLE biomarker, especially for ANA-negative patients.

A significant challenge is the variability of assays used to detect anti-Rib-P — and the fact that their identification varies with the detection method.

The EliA Rib-P test was designed to have optimal sensitivity (true-positive rate) and specificity (true-negative rate), and can be used to support the diagnosis of SLE, particularly in patients negative for ANAs.

Autoantibodies against RNA Pol III are a criteria marker for SSc and may be the only disease-associated autoantibodies in up to 70% of patients positive for them. According to Thermo Fisher, the EliA RNA Pol III test is the first fully automated RNA Polymerase test available in the U.S.

ribosomal P’, ‘anti-ribosomal P