SIGLEC1 and systemic lupus erythematosus: Similarly to surface SIGLEC-1 expression, sSIGLEC-1 concentrations were markedly increased in SLE patients (10.4 ng/ml, 95% CI 8.8–12.2) compared to healthy controls (5.78 ng/ml, 95% CI 5.5–6.0, P = 9.6 × 10− 12; Fig. 4a) in the combined discovery and replication cohorts of 75 SLE patients and 504 healthy donors.