A study presented at the Annual European Congress of Rheumatology (EULAR) 2017 showed that a new epitope–based blood test designed to detect SSc–specific autoantibodies may be helpful as a tool for diagnosis in patients suspected of having SSc.

Previous studies have identified a specific epitope (PDGFRalpha) that is recognised by autoantibodies in patients with SSc, can be cloned from memory B white blood cells from an SSc patient, and can induce fibrosis within a living organism. Peptides (protein fragments) making up this epitope have been shown to be specifically recognised by an immunoglobulin (IgG) in the blood of patients with SSc, but not of controls.

In this latest study, one of these peptides – a so–called "immunodominant peptide" – has been used to develop a specific blood test which can be used to diagnose SSc.

"Our preliminary results suggest that this new blood test to detect SSc–specific, agonistic, autoantibodies may identify those SSc patients with active disease, regardless of the 'limited vs diffuse' extension of their disease," said lead author Dr. Gianluca Moroncini from Università Politecnica Marche, Ancona, Italy. "We propose using this assay for the prospective screening of large groups of patients affected by, or suspected of suffering from SSc to properly validate it as a tool for disease activity assessment and / or the early diagnosis of SSc," he added.

"Although we have initial data on the specificity of the test i.e. its ability to discriminate between SSc patients with active disease from patients with inactive disease, no data are available as yet on early diagnosis. The VEDOSS cohort would be an ideal target for assessing the utility of this new test in the early identification of active / progressive forms of SSc," Dr. Moroncini concluded.

The first step in this new study involved the identification of one specific peptide that could effectively discriminate SSc from healthy control blood samples from a large PDGFRalpha peptide library, which had been used for epitope mapping of monoclonal anti–PDGFR? antibodies among a population of 25 SSc and 25 healthy control blood samples.

Then, using a second smaller PDGFRalpha peptide library, the identity of this one immunodominant epitope was confirmed.

Statistical analysis identified two subgroups of SSc samples: reactive vs nonreactive, the latter undistinguishable from the healthy controls. A third peptide library was then used to identify the peptide recognised exclusively by the reactive SSc blood samples, taken from patients with active, progressive disease, whereas the nonreactive SSc samples were taken from subjects with less active, non–progressive disease.