C4A and systemic lupus erythematosus: According to Pearson's correlation analysis, it revealed a moderately negative correlation between serum SRSR and SLEDAI score in SLE patients (r = −.483, P < .05); there were a slight negative connection with ESR (r = −.226, P < .05), a slight positive connection with C3 (r = .331, P < .05), a slight positive correlation with C4 (r = .324, P < .05), a moderately negative correlation with CRP (r = −.514, P < .05), and no correlation with anti‐dsDNA (r = −.057, P = .445).