Healthy first-degree relatives of individuals with HLA-B27–positive axial spondyloarthritis who also were HLA-B27 positive were at increased risk for developing the disease themselves within 1 year, based on data from an ongoing prospective cohort study that involved 202 first-degree relatives.

Axial spondyloarthritis (axSpA) generally arises between ages 18 and 40 years, but diagnosis can be delayed, in part because of the lack of biomarkers and nonspecific symptoms, wrote Henriëtte M.Y. de Jong, MD, PhD, of the University of Amsterdam, and colleagues.

Individuals who carry the HLA-B27 gene are predisposed to axSpA, and their first-degree relatives (FDRs) are at increased risk as well, the researchers said. Therefore, “studying [FDRs] could help to identify clinical signs, imaging abnormalities, and biomarkers that are predictive of development of axSpA,” they said.

In a study published in Arthritis Care & Research, the investigators reviewed data from patients in the Pre-SpA cohort, a 5-year prospective study of healthy-seeming FDRs of patients with HLA-B27–positive axSpA. The researchers previously reported that up to one-third of 51 FDRs had clinical features associated with SpA at baseline, despite the lack of a diagnosis.

The current study included an additional 151 FDRs who had answered yearly questions about back pain and undergone a yearly physical exam and plain radiographs and MRI imaging at baseline.

Overall, 65% reported back pain at baseline and 19% met criteria for inflammatory back pain, with a median visual analog score (VAS) for back pain of 22. No active arthritis was noted, but 5 FDRs reported a past arthritis diagnosis, 48 reported arthralgia, and 16 had at least one tender joint on physical exam. Eight FDRs had past diagnoses of enthesitis, and one had a history of dactylitis.

In assessing disease activity, the researchers found an elevated C-reactive protein (CRP) level in 24 FDRs and 11 had an elevated erythrocyte sedimentation rate (ESR).

On MRI of the sacroiliac joint at baseline, 10% of the FDRs had SPARCC (Spondyloarthritis Research Consortium of Canada) scores of 2 or higher, 4% had scores of 5 or higher, and 4% had deep lesions.

A total of 123 FDRs had complete data at a 1-year follow-up visit.

“All features were equally distributed between HLA-B27–positive and –negative FDRs,” the researchers noted. However, at the end of the 1-year follow-up period, seven (6%) of the FDRs were clinically diagnosed with axSpA, and six of them were HLA-B27 positive. Disease activity measures had increased at 1 year in all seven patients with newly diagnosed axSpA.

The study findings were limited by several factors, including the possible channeling of FDRs with current complaints of back pain into the study and the inability to confirm details of family and medical history, the researchers noted. However, the VAS back pain scores reported by the FDRs suggest that this pain was not a fixture in daily life, they wrote.

The results confirm the prevalent subclinical signs of SpA in healthy FDRs of patients with axSpA who were positive and negative for HLA-B27, but also confirm that clinical progression occurred primarily in the HLA-B27–positive patients in conjunction with inflammatory back pain, the researchers said.

“Further follow-up of the Pre-SpA cohort will give more robust insight into the characteristics of FDRs that progress towards clinical SpA, thereby hopefully enabling the characterization of high-risk FDRs,” they concluded.

The Pre-SpA cohort is supported by the Dutch Arthritis Society. Lead author de Jong had no financial conflicts to disclose. One coauthor is employed by UCB, and several others disclosed relationships with AbbVie, Eli Lilly, Janssen, Novartis, Pfizer, and UCB.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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