Frequency of anti-CD74 antibodies is a promising tool to support the clinical diagnosis of axial spondyloarthritis (axSpA), according to study results published in Rheumatology.
Individuals with vs without axSpA have been shown to have higher levels of anti-CD74 antibodies, introducing the possibility of these antibodies as an important diagnostic marker.
A study of patients with axSpA was conducted to determine the role of anti-CD74 antibodies in axSpA diagnosis, activity, and duration. Patients with rheumatoid arthritis (RA) and healthy control participants were also included in the study. Researchers conducted laboratory tests and measured Ankylosing Spondylitis Disease Activity Score to determine disease activity. They also performed anti-CD74 antibody detection for all participants.
A total of 50 patients with axSpA (25 women), 15 with RA, and 15 healthy control participants were eligible for the study. Results indicated that levels of CD74 autoantibodies were significantly higher in patients with axSpA vs those with RA and the healthy control participants (80% vs 20% and 13.3%, respectively; P <.001). There were no significant differences in the frequency of CD74 autoantibodies between patients with early and late disease (P =.629). A total of 83% of patients with active disease vs 33.3% with inactive disease tested positive for CD47 autoantibodies (P =.037). Most patients with articular and extra-articular manifestation of axSpA were observed to be antibody-positive. There were no correlations detected between levels of anti-CD47 antibodies and either age or sex.
Researchers revealed that the sensitivity of anti-CD47 antibodies in the axSpA group was 80% vs both the control groups, with 80% and 87% specificity vs the RA and healthy control groups, respectively (P <.001). In the axSpA group, levels of antibodies in patients with positive disease activity was found to be much greater than those with negative disease activity.
The main limitation of the study was the small sample size.
Researchers concluded, “Based on the sensitivity and specificity of anti-CD74 IgG, this is a promising diagnostic tool to support the clinical diagnosis of axSpA.”
Abdelaziz MM, Gamal RM, Ismail NM, Lafy RA, Hetta HF. Diagnostic value of anti-CD74 antibodies in early and late axial spondyloarthritis and its relationship to disease activity. Published online July 24, 2020. Rheumatology. doi:10.1093/rheumatology/keaa292