Anti-CD74 antibodies in spondyloarthritis: A systematic review and meta-analysis

There is still an unmet need for a simple and reliable biomarker for the diagnosis of spondyloarthritis. Recent studies indicated that anti-CD74 antibody could act as a biomarker for spondyloarthritis. Therefore, this review aims to evaluate the levels of anti-CD74 IgG and IgA antibodies in spondyloarthritis and the diagnostic value of anti-CD74 antibodies. PubMed, Web of Science and Medline were comprehensively searched from inception to August 7th, 2019. The pooled standard mean difference (SMD) with 95% confidence interval (CI) was used to estimate the differences of the levels of anti-CD74 IgG and IgA antibodies between spondyloarthritis patients and controls. Sensitivity, specificity and summary receiver operating characteristics (SROC) curve were used for evaluating the diagnostic value of anti-CD74 antibodies. The use of fixed-effect or random-effects model depended on heterogeneity. Among 55 searched studies, 9 studies were finally included for analysis. Anti-CD74 IgG and IgA antibodies were both significantly increased in spondyloarthritis patients compared with matched controls (IgG: SMD = 0.88, 95% CI = 0.55 to 1.21; IgA: SMD = 0.98, 95% CI = 0.68 to 1.28). The pooled sensitivity, specificity and area under the SROC curve of anti-CD74 IgG antibodies were 0.61, 0.90 and 0.8881, while these indicators of anti-CD74 IgA antibodies were 0.59, 0.95 and 0.8671, respectively. Anti-CD74 IgG and IgA antibodies were significantly increased in spondyloarthritis patients and suggest a high diagnostic specificity of spondyloarthritis. Anti-CD74 antibody could potentially be a biomarker for the diagnosis of spondyloarthritis, but many open questions remain.