VIENNA — Anti-Ro/SSA antibodies may help predict which patients with systemic sclerosis (SSc) are at a greater risk for interstitial lung disease (ILD) and may serve as a biomarker to guide screening, according to an analysis of data from a large European cohort.
The researchers were led by Blaž Burja, MD, PhD, a physician-scientist at the Center of Experimental Rheumatology, University Hospital Zürich, Zürich, Switzerland, who reported that anti-Ro/SSA antibodies are a risk factor for ILD, with an odds ratio of 1.24, in patients with SSc.
At the European Alliance of Associations for Rheumatology (EULAR) 2024 Annual Meeting, he presented the findings of the study that aimed to find out if SSc-nonspecific antibodies might help better risk-stratify patients with SSc, focusing on lung involvement. "Among them, anti-Ro/SSA antibodies have been shown to be associated with interstitial lung disease in different connective tissue diseases," Burja pointed out.
"A total of 15% of all patients in the SSc cohort presented with anti-Ro/SSA antibodies, and this subgroup presented with distinct clinical features: Importantly, higher prevalence of ILD and lower DLCO% [diffusing capacity of the lungs for carbon monoxide] in patients with established ILD," reported Burja, adding that, "However, these anti-Ro/SSA antibodies do not predict ILD progression, death, or overall disease progression."
Based on the findings, Burja suggested that these antibodies be incorporated into routine clinical practice to identify patients with SSc who have a high risk for ILD. He noted that "this has specific importance in clinical settings without availability of high-resolution computed tomography (HRCT), where anti-Ro/SSA antibodies could represent an additional biomarker to guide the screening process, in particular, in patients without SSc-specific antibodies."
Caroline Ospelt, MD, PhD, co-moderator of the session and scientific program chair of EULAR 2024, told Medscape Medical News that the study was unique in its approach to studying ILD risk by "looking outside the box, so not just at specific antibodies but whether cross-disease antibodies may have value in stratifying patients and help predict risk of lung involvement and possibly monitor these patients."
Ospelt, who is a professor of experimental rheumatology at University Hospital Zürich and was not involved in the study, noted that "It might also be the case that we could adapt this concept and use these antibodies in other rheumatic diseases, too, not just systemic sclerosis, to predict lung involvement."
Risk-Stratifying With SSc-Nonspecific Antibodies
Burja explained that despite better stratification of patients with SSc with SSc-specific antibodies, "in clinical practice, we see large heterogeneity, and individual prognosis with regards to outcomes is still unpredictable, so we wanted to know whether by using nonspecific autoantibodies we might be better able to risk-stratify these patients."
A study population of 4421 with at least one follow-up visit, including 3060 patients with available follow-up serologic data, was drawn from the European Scleroderma Trials and Research group database (n = 22,482). Of these 3060 patients, 461 were positive for anti-Ro/SSA antibodies and 2599 were negative. The researchers analyzed the relationships between baseline characteristics and the development or progression of ILD over 2.7 years of follow-up. Incident, de novo ILD was defined based on its presence on HRCT, and progression was defined by whether the percentage of predicted forced vital capacity (FVC%) dropped ≥ 10%, FVC% dropped 5%-9% in association with a DLCO% drop ≥ 15%, or FVC% dropped > 5%. Deaths from all causes and prognostic factors for the progression of lung fibrosis during follow-up were recorded.
High Prevalence of ILD With Anti-Ro/SSA Antibodies in SSc
At baseline, patients with anti-Ro/SSA antibodies were aged 55-56 years, 84%-87% were women, and muscular involvement was present in 18% of patients positive for anti-Ro/SSA antibodies and 12.5% of those who were negative (P < .001). According to HRCT, ILD was present in 56.2% of patients positive for anti-Ro/SSA antibodies and in 47.8% of those who were negative (P = .001). FVC% was 92.5% in patients positive for anti-Ro/SSA antibodies and 95.7% in those who were negative (P = .002). DLCO% was 66.9% in patients positive for anti-Ro/SSA antibodies and 71% in those who were negative (P < .001).
"A total of 15% of all SSc patients presented as positive for anti-Ro/SSA antibodies, and these patients all presented with higher prevalence of SSA-nonspecific antibodies, too: Of note, those with anti-La/SSB and anti-U1/RNP and rheumatoid factor," Burja reported.
In patients with anti-U1/RNP autoantibodies, 1% were positive and 4% were negative for anti-Ro/SSA antibodies; in those with anti-La/SSB autoantibodies, 17% were positive and 1% were negative for anti-Ro/SSA antibodies; and in those with rheumatoid factor, 28% were positive and 14% were negative for anti-Ro/SSA antibodies.
Burja pointed out that the average disease duration in the study cohort at baseline was 7 years, "and at this timepoint, we expect to see some common disease manifestations. Specifically, higher muscular involvement and higher ILD based on HRCT."
"We decided to focus on patients with established ILD at baseline," said Burja, "Anti-Ro/SSA-positive patients with established ILD at baseline presented with lower DLCO values at 59% in patients positive for anti-Ro/SSA antibodies and 61% for those who were negative," Burja said.
After conducting a multivariable analysis of 14,066 healthcare visits and adjusting for known risk factors for ILD, the researchers concluded that anti-Ro/SSA antibodies are an independent risk factor for ILD, with an odds ratio of 1.24 (95% CI, 1.07-1.44; P = .006). They also determined that anti-Ro/SSA antibodies are a risk factor for lower DLCO values in patients with ILD, with a regression coefficient of −1.93.
The researchers then explored the progression of ILD and overall disease progression and survival during the follow-up period in a longitudinal analysis. "However, anti-Ro/SSA antibodies were not found to predict the progression of ILD," reported Burja, adding that this was true regardless of the definition of ILD progression used. "Nor did anti-Ro/SSA antibodies predict survival or overall disease progression."
Burja pointed out the limitations in his study, including the lack of standardized criteria for all centers to assess anti-Ro/SSA positivity; there was a lack of discrimination between anti-Ro52 and anti-Ro60 subtypes, and there were no standardized applicable criteria to study lung progression in SSc.
Burja and Ospelt had no relevant financial disclosures.