C3 and systemic lupus erythematosus: S.ANA - serum antinuclear antibody; S.dsDNA - serum double-stranded DNA; C3, C4 - complements 3 and 4; NSAIDs - non-steroidal anti-inflammatory drugs; SLE - systemic lupus erythematosus; DM - diabetes mellitus; SHT - subclinical hypothyroidism