Karp, David R.

ObjectiveSystemic lupus erythematosus (SLE) and other autoimmune diseases cause significant morbidity. Identifying populations at risk of developing SLE is essential for curtailing irreversible inflammatory damage. The aim of this study was to identify factors associated with transition to classified disease that would inform our understanding of the risk of SLE.MethodsPreviously identified blood relatives of patients with SLE, who had <4 American College of Rheumatology (ACR) classification criteria for SLE at baseline, were enrolled in this follow‐up study (n = 409 unaffected relatives). Participants provided detailed family, demographic, and clinical information, including the SLE‐specific portion of the Connective Tissue Disease Screening Questionnaire (SLE‐CSQ). Serum and plasma samples were tested for the presence of lupus‐associated autoantibodies and 52 soluble mediators. Generalized estimating equations (GEEs) were applied to identify factors predictive of disease transition.ResultsOf the 409 unaffected relatives of SLE patients, 45 (11%) had transitioned to classified SLE at follow‐up (mean time to follow‐up 6.4 years). Relatives who transitioned to SLE displayed more lupus‐associated autoantibody specificities and higher SLE‐CSQ scores (P < 0.0001) at baseline than did relatives who did not transition. Importantly, those who had developed SLE during the follow‐up period also had elevated baseline plasma levels of inflammatory mediators, including B lymphocyte stimulator, stem cell factor (SCF), and interferon‐associated chemokines (P ≤ 0.02), with concurrent decreases in the levels of regulatory mediators, transforming growth factor β (TGFβ), and interleukin‐10 (P ≤ 0.03). GEE analyses revealed that baseline SLE‐CSQ scores or ACR scores (number of ACR criteria satisfied) and plasma levels of SCF and TGFβ, but not autoantibodies, were significant and independent predictors of SLE transition (P ≤ 0.03).ConclusionPreclinical alterations in levels of soluble mediators may predict transition to classified disease in relatives of SLE patients. Thus, immune perturbations precede SLE classification and can help identify high‐risk relatives for rheumatology referral and potential enrollment in prevention trials.