SAN DIEGO — Clinically significant interstitial lung disease (ILD) is believed to occur in 5%-10% of patients with rheumatoid arthritis (RA), but robust data are lacking on how to best predict which patients face the highest risk for RA-associated ILD. However, the results of several studies presented at the American College of Rheumatology annual meeting indicate that researchers are making strides in this field of rheumatologic care.
Adding Genetic Factors Improves ILD Risk Prediction
In the realm of risk stratification, Austin M. Wheeler, MD, a rheumatology fellow at the University of Nebraska Medical Center, Omaha, discussed the development and validation of a combined clinical and genetic risk score for ILD. “There is clear and well documented phenotypic and genetic overlap of ILD with idiopathic pulmonary fibrosis (IPF),” Dr. Wheeler said. “A number of clinical risk factors have been described for RA-ILD, including older age, male sex, smoking history, higher disease activity, and seropositivity. There are also well-documented genetic risk factors for RA-ILD. The MUC5B genetic variant is the strongest risk factor for IPF, and it’s been described in RA-ILD as well.”
Dr. Wheeler
Dr. Austin M. Wheeler
A recently published study indicated that a genetic risk score without the MUC5B variant improved predictive ability for IPF and interstitial lung abnormalities better than using the MUC5B variant alone, “but no prior attempts have been made at developing a composite genetic risk score in RA-ILD” using both genetic and clinical risk factors, he said.
For the current study, Dr. Wheeler and colleagues drew from 2,386 participants in the Veterans Affairs Rheumatoid Arthritis (VARA) Registry, a multicenter, prospective cohort of US veterans with rheumatologist-diagnosed RA and who fulfilled the 1987 ACR classification criteria. The researchers validated ILD through a systematic review of medical records, including clinical diagnosis of ILD plus either imaging or lung biopsy findings, and collected whole genome data that included 12 single nucleotide polymorphisms (SNPs) previously identified to be associated with risk for RA-ILD. They then used a meta-analytic approach to create pooled associations for each of those respective SNPs using data from the VARA registry participants as well as participants from the past study where the SNPs were first identified. “Those pooled associations were what we used for our effects size within the genetic risk score,” which ended up using five of the SNPs, Dr. Wheeler explained. Next, he and his colleagues combined the genetic risk score with clinical risk factors including age, sex, smoking history, disease activity, and rheumatoid factor (RF) positivity to create their combined risk score.
The mean age of the cohort was 70 years, 89% were male, 78% had a smoking history, and 78% were anti–cyclic citrullinated peptide (CCP) antibody positive. Of the 2,386 participants, 224 (9.4%) had RA-ILD. The full composite risk score had the highest area under the receiver operating curve (AUC) of 0.67, compared with an AUC of 0.623 using the clinical factors alone, 0.651 using the clinical factors plus only the MUC5B variant, and 0.654 using the composite score minus only the MUC5B variant. These AUCs show that “the combined risk score performs better than clinical factors even without the inclusion of the MUC5B variant in the score, which is notable because it supports the importance of further investigation into polygenic risk scores in RA-ILD as there is clearly more at play in a patient’s overall genetic risk,” Dr. Wheeler said.
As an example of the composite score’s ability to discriminate between people with and without RA-ILD, a cutpoint of 0.05 gave a sensitivity of 90.2% and would have eliminated about 25% of the cohort from unnecessary high-resolution CT scans and pulmonary function tests, he said.
“This study demonstrates the potential utility of genetic risk scores in RA-ILD identification and supports further investigation into individual risk stratification and screening,” he concluded. “This isn’t ready for clinical applicability by any means, but I think it serves as a proof of concept of the idea of a genetic risk score in RA-ILD.”