[Usefulness of the standardized serum cystatin C reagent in evaluation of renal function]

Serum cystatin C (sCysC) is valuable to evaluate the renal functions in various clinically studies. Since the reagents to detect sCysC are different among institutes or hospitals, the accidental error due to the difference of reagents is not negligible. That is why sCysC is sometimes difficult to use or interpret for patient as estimated Glomerular filtration rate (eGFR) that is one of the most popular factors to evaluate renal function. Recently, the international reference standard is gradually accepted as standardization of chemical measurement of sCysC in Japan. Japan Society of Clinical Chemistry has reported the utilities for sCysC measurement standardization in 2010. In this study, we examined the usefulness of the standardization of sCysC reagent in Chiba University Hospital. Our study indicated that the clinical usefulness of eGFR calculated by sCysC. As results, eGFR from serum creatinine (sCr) was relatively high in patients with reduced muscle mass, such as old-age patients with wheelchair and prolonged hospitalization. On the other hand, eGFR from sCysC was high in patients with hypothyroidism. Together, eGFR calculated by sCysC is clinically available for the patients with reduced muscle mass could be underestimated. Further studies are required to evaluate the validity of standardization of sCysC measurement and find the dissociation among eGFR, sCysC and sCr depending in the renal disease or pathogenesis.