The aim of this work was to develop a simple assay to distinguish between patients with rheumatoid arthritis (RA) and patients with systemic lupus erythematosus (SLE) by measuring the serum sialylated IgG (SAIgG).
Using a newly established SNA-based ELISA method, we compared the sialylation of immunoglobulin G (IgG) from a healthy control group (n = 41), RA patients (n = 30), SLE patients (n = 45), patients with neuropsychiatric SLE (NPSLE) (n = 30) and patients with juvenile idiopathic arthritis (JIA) (n = 32).
The average SAIgG level in healthy control individuals, RA patients, JIA patients, SLE patients and NPSLE patients was 0.64 ± 0.17, 0.82 ± 0.33, 0.69 ± 0.23, 0.12 ± 0.02 and 0.03 ± 0.01 mg/ml, respectively. The ratio of sialylated IgG to total IgG was significantly decreased in the SLE group (1.88 ± 0.32%) compared with the healthy population (4.64 ± 0.90%).
In summary, while the mean serum SAIgG level of RA and JIA patients was similar to that of the healthy population, there was a significant decrease in the serum SAIgG of both SLE groups tested, whereby the level of the NPSLE population group was the lowest.