Aims: Urinary cystatin C has been suggested as a useful biomarker for diagnosis of acute kidney injury (AKI). Multiple myeloma is often complicated by AKI. Therefore, we investigated whether the urinary cystatin C was available for diagnosis of AKI in multiple myeloma.
Materials and methods: This study included 39 patients with monoclonal gammopathy of undetermined significance (MGUS) or multiple myeloma. We reviewed the medical records retrospectively and investigated whether urinary γ-globulin and myeloma progression had effects on urinary cystatin C excretion.
Results: Spearman's correlation analysis showed that serum β2-microglobulin and serum cystatin C had a significant positive correlation with the urinary cystatin C excretion (r = 0.513, p = 0.001, r = 0.659, p < 0.001) and FEcystatinC (r = 0.585, p = 0.002, r = 0.711, p < 0.001). The GFRcr also had a significant negative correlation with the urinary cystatin C excretion (r = -0.582, p < 0.001) and FEcystatinC (r = -0.474, p = 0.002). In addition, the urinary γ-globulin had a significant positive correlation with the urinary cystatin C excretion (r = 0.678, p < 0.001) and FEcystatinC (r = 0.731, p < 0.001). Urinary γ-globulin was the most significant factor to influence urinary cystatin C excretion in multiple regression test.
Conclusion: These results indicate that urinary γ-globulin and myeloma progression can increase the fractional and total excretion of urinary cystatin C. Therefore, it is believed that the urinary cystatin C can be affected by urinary γ-globulin and myeloma progression in the diagnosis of AKI in multiple myeloma. In addition, urinary γ-globulin is believed to be the most significant factor to influence on urinary cystatin C.