Background and aims Complement activation is one of the important pathogenesis of systemic lupus erythematosus (SLE), and it has been revealed to associate with the activity of SLE. Complement regulatory proteins (CRPs) play critical roles on the regulation of alternative complement pathway, however, studies focus on the CRPs during SLE flare-up remains limited. This study was to investigate the change of CRPs and end products of compliment activation on active and remission phases of SLE.

Methods Forty paediatric SLE patients were enrolled. The clinical manifestation, laboratory data, and serum CRPs, C5a, and C5b-9 on active and remission phases were analysed.

Results The mean age of patients was 13.9±3.8 years with female predominant (7:1). The mean renal and non-renal SLEDAI at active and remission phases were 4.25 vs 0.45 and 8.32 vs 1.25, respectively. Fever, rash, and arthritis were the most common features and kidney was the most common involved organ at active phase. The mean serum complement factor H and I levels at active phase were significantly lower than that at remission phase. The mean serum CD46 level at active phase was higher significantly compared with that at remission phase. The serum C5a and C5b-9 at active and remission phases were no significant difference. Five patients had sequelae including 1 intracranial haemorrhage and 4 chronic kidney disease.

Conclusions Serum complement factor H, I and CD46, but not C5a and C5b-9 were associated with disease activity of SLE.