Understanding kidney function assessment: the basics and advances.

PURPOSE: Multiple kidney function assessment modalities are available, but their appropriateness is constantly questioned. This review provides practitioners with in-depth understanding of kidney function assessment methods, their clinical utility, and comparisons. DATA SOURCES: PUBMED search was conducted by relevant subject headings.
CONCLUSIONS: Glomerular filtration rate (GFR) is the best indicator of kidney function. Exogenous compounds like inulin help measure GFR, but endogenous substances (like creatinine) are more convenient, although exhibiting greater variability. Cystatin C is advocated as a functional marker; its clinical significance is under study. Proteinuria adds value to GFR estimation. There are commonly used equations estimating GFR like the creatinine-based Cockcroft-Gault and the modification of diet in renal disease. The new creatinine-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation demonstrates higher accuracy of patient classification in earlier stages of disease. Recently, the Chronic Renal Insufficiency Cohort (CRIC) study has devised an equation combining serum creatinine and cystatin C in longitudinal modeling of kidney function. IMPLICATIONS FOR PRACTICE: Current GFR estimation methods have limitations, and are useful for populations they have been tested in. Practitioners should be well informed on emerging equations that provide greater accuracy in CKD diagnosis; this would help implement appropriate prevention and intervention strategies. ©2013 The Author(s) ©2013 American Association of Nurse Practitioners.