C4A and Decreased total leukocyte count: The criteria for positivity or diagnosis of each indicator are as follows: ANA, was defined as positive when the titer was ≥1:160; the positivity ofanti-SsA, anti-SsBand theumatoid factor was determined according to the cut-off values set by the reference laboratory; hypergammaglobulinemia was diagnosed when the total immunoglobulin accounted for ≥20% of the total proteins; leukopenia was diagnosed when the white blood cell count was <4,000/mm3; hypocomplementemia was diagnosed when the C3 level was <80 mg/dL and/or the C4 level was <15 mg/dL.