Early diagnostic tools for systemic sclerosis
medwireNews: Two studies presented at the Annual European Congress of Rheumatology (EULAR) 2017 in Madrid, Spain, have highlighted new tools that could help diagnose systemic sclerosis (SSc) in the early stages, supporting the EULAR campaign: “Don’t delay, Connect Today!”
The first tool, nailfold videocapillaroscopy (NVC), is a non-invasive imaging method that uses a microscope and accompanying video camera to measure morphologic changes in the peripheral microcirculation.
Vanessa Smith, from Ghent University Hospital in Belgium, reported her team’s data showing that among 1085 patients with Raynaud’s phenomenon, a typical “early” NVC pattern was seen in 40% of 622 patients who tested positive for anti-nuclear antibody (ANA), compared with 13% of 227 patients who tested negative.
The early quantitative capillaroscopic characteristic of moderate or extensive giant capillaries also differed significantly between the two groups, seen in 23% of those testing positive for ANA versus 5% of those testing negative, whereas there was no significant difference in microvascular damage consistent with more advanced SSc, such as loss of capillaries and abnormally shaped capillaries.
Among a target group of 555 of the patients with Raynaud’s phenomenon who tested positive for ANA, had quantitative capillaroscopic alterations, and were also positive for SSc autoantibodies, 79% had an early NVC pattern for SSc. This compared with 0% of a control group of 195 with Raynaud’s phenomenon who were negative for all these variables.
Smith told the press: “One of the aims of studying the disease in such an early cohort is to find targets to ultimately treat the disease before irreversible tissue damage has occurred.”
She believes that nailfold videocapillaroscopy should be a “key” component of the very early diagnosis of systemic sclerosis (VEDOSS) criteria, which includes Raynaud’s phenomenon, antinuclear antibodies in the circulation, and puffy digits.
The second tool is an epitope-based assay that detects SSc-specific autoantibodies in the blood. The epitope involved is the conformational PDGFRα epitope.
Gianluca Moroncini (Universitá Politecnica Marche, Ancona, Italy) and colleagues identified an immunodominant peptide of the epitope that was specifically recognized by immunoglobulin G in the blood of 25 patients with SSc, including 12 with limited disease and 13 with diffuse SSc, but not in the blood of 25 individuals without SSc.
The identity of this immunodominant peptide was confirmed in the same 50 serum samples using a second smaller PDGFRα peptide library of the top 20 conformational binders.
And a third PDGFRα peptide library correctly identified the chimeric peptide recognized exclusively by “reactive” blood samples from SSc patients with active, progressive disease from “nonreactive” samples from SSc patients with less active, non-progressive disease, which were indistinguishable from those of healthy individuals.
Moroncini noted that “this novel test may identify SSc patients with active disease, regardless of the canonical ‘limited vs diffuse’ classification.”
He proposes the test for “the prospective screening of large groups of patients affected by, or suspected of suffering from SSc and/or early diagnosis.”
But he recognizes that the test’s ability to discriminate patients in the early diagnosis of the disease now needs to be validated in a large group of patients, such as the VEDOSS cohort.
The presenters were in agreement that it could be feasible to combine the NVC and epitope-based tests to further improve the diagnosis of early Ssc.
By Lucy Piper
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