Humoral immune function: complement C3: 0.876 g/L (slightly lower); urine total protein 5.30 g/24 h; The results from all the following tests were normal: erythrocyte sedimentation rate, coagulation, urine red blood cell morphology, hepatitis B, autoantibodies, antineutrophil cytoplasmic antibodies (ANCA), proteinase-3 (PR3), MPO (myeloperoxidase), urine and blood light chain. Here, MPO is linked to hepatitis B virus infection.