Table 3.
eGFRcr | eGFRcys | Urine ACR | |
---|---|---|---|
Primary use* | Initial test for assessment of GFR | Confirmatory test for assessment of GFR | Initial test for assessment of albuminuria |
Non-steady state (AKI) | Change in eGFR lags behind the change in mGFR (eGFR overestimates mGFR when mGFR is declining and underestimates mGFR when mGFR is rising) | Change in eGFR lags behind the change in mGFR (eGFR overestimates mGFR when mGFR is declining and underestimates mGFR when mGFR is rising) | ACR overestimates AER when mGFR is declining (creatinine excretion is decreased) and underestimates AER when mGFR is rising (creatinine excretion is increased) |
Non-GFR factors** | Directly measured in clinical studies | Hypothesized from clinical observations and epidemiologic studies | NA |
Factors affecting generation | Decreased by large muscle mass, high protein diet, ingestion of cooked meat and creatine supplements Increased by small muscle mass, limb amputation, muscle wasting diseases | Decreased in hyperthyroidism, glucocorticoid excess, and possibly obesity, inflammation and smoking Increased in hypothyroidism |
Decreased by large muscle mass (higher urinary creatinine concentration) Increased by small muscle mass (lower urinary creatinine excretion). |
Factors affecting tubular reabsorption of secretion | Decreased by drug-induced inhibition of secretion (trimethoprim, cimetidine, fenofibrate) | NA | NA |
Factors affecting extra-renal elimination | Decreased by inhibition of gut creatininase by antibiotics Increased by dialysis, large losses of extracellular fluid (drainage of pleural fluid or ascites) |
Increased by large losses of extracellular fluid (drainage of pleural fluid or ascites) | NA |
Range | Less precise at higher GFR, due to higher biological variability in non-GFR determinants relative to GFR, and larger measurement error in SCr and GFR | Less precise at higher GFR, due to higher biological variability in non-GFR determinants relative to GFR, and larger measurement error in SCysC and GFR | Less precise at lower ACR, due to higher biologic variability in AER, and larger measurement error in urine albumin concentration |
Interference with assays | Spectral interferences (bilirubin, some drugs) Chemical interferences (glucose, ketones, bilirubin, some drugs) | NA | Very high urine albumin concentration (“prozone effect”) |
Interfering conditions | NA | NA | Contamination with albumin in menstrual blood and lower urinary tract inflammation |
Reference test for GFR is measured GFR (mGFR) using clearance methods; reference test for albuminuria is albumin excretion rate (AER) in timed urine collection.
Effects of factors affecting non-GFR determinants refer to effects on eGFR
Abbreviations: GFR, glomerular filtration rate; ACR, albumin-to-creatinine ratio; AER, albumin excretion rate; SCr, serum creatinine; SCysC, serum cystatin C; AKI, acute kidney injury