[Development of evaluation of kidney function and classification of chronic kidney disease (CKD)--including CKD clinical practice guide 2012].

Chronic kidney disease (CKD) Clinical Practice Guide 2012 for Japanese (CKD guide 2012) was released to update CKD guide 2009. Classification of CKD was altered according to the classification of KDIGO 2012 CKD Clinical Practice Guideline, which was based on cause, glomerular filtration rate (GFR) categories, and albuminuria categories. Because evaluation of albuminuria is not common for most CKD subjects in Japan, proteinuria categories comparable to the albuminuria categories were added to CKD Guide 2012. A GFR equation based on serum creatinine is recommended and has been used for evaluation of renal function. In CKD Guide 2012, a GFR equation based on serum cystatin C was also included. Serum cystatin C is a new GFR marker. Recently, measurement of cystatin C was standardized using international certified reference material ERM-DA471/IFCC. A new GFR equation based on standardized serum cystatin C was developed for Japanese. Estimated GFR based on serum creatinine (eGFRcreat) is influenced by not only renal function but also muscle mass. It might be overestimated in subjects with low muscle mass, such as muscle wasting diseases, and underestimated in those with high muscle mass, such as athletes. Estimated GFR based on serum cystatin C (eGFRcys) is little-influenced by muscle mass. If eGFRcreat is less accurate, additional evaluation of eGFRcys is useful. Generally, the average value of eGFRcreat and eGFRcys(eGFRaverage) is most accurate.