C4A and systemic lupus erythematosus: We found a significant association between SLE reclassification and thrombocytopenia (p = 0.0001), serositis (p = 0.02), joint involvement (p = 0.03), low levels of C3 and C4 (p = 0.03, p = 0.0001, respectively), positivity for anti-dsDNA/anti-Sm (p =  < 0.0001).