C4A and hepatitis B virus infection: No obvious abnormalities were observed in routine blood tests, blood coagulation, erythrocyte sedimentation rate, hepatitis B, hepatitis C, syphilis, acquired immunodeficiency syndrome, rheumatoid factor, immunoglobulin M, immunoglobulin E, immunoglobulin A, immunoglobulin G, antinuclear antibody, blood complement C3, blood complement C4, and autoimmune antibodies.