Abstract: Objective: To investigate the value of the serum IgA,ratios of IgA/C3 and IgA/C4 in the differential diagnosis of primary IgA nephropathy and non-IgA nephropathy.Methods: The serum levels of IgA,C3 and C4 in 64 IgA nephropathy patients and 67 non-IgA nephropathy patients were detected using turbidimetric immunoassay,the ratios of IgA/C3 and IgA/C4 were calculated,the ROC curve were established,and the area under the curve was calculated.The significance of the serum IgA,ratios of IgA/C3 and IgA/C4 in predicting the IgA nephropathy was evaluated.Results: The serum IgA level,ratios of IgA/C3 and IgA/C4 in patients with primary IgA nephropathy significantly increased compared with other nephrotic patients(P<0.01),and the area under the ROC curve of the IgA,ratios of IgA/C3 and IgA/C4 was 0.692,0.718 and 0.747,respectively.Conclusions: In the absence of pathological diagnosis of renal biopsy,the IgA,ratios of IgA/C3 and IgA/C4 can play an auxiliary role in the differential diagnosis of primary IgA nephropathy.