3. What is GFR and why is it a more accurate measure than simply getting a creatinine level?

Use of GFR or glomerular filtration rate is becoming more common as a standard for evaluating patient prior to contrast media injection. GFR is potentially more accurate as it takes into account creatinine levels but also patient weight, age, sex and race. "A significantly higher number of outpatients scheduled for contrast medium-enhanced CT met the National Kidney Foundation criteria for renal insufficiency when the MDRD equations were used to estimate the glomerular filtration rate compared witht the number of outpatients who met the criteria on the basis of elevated creatinine levels." Identifying Outpatients with Renal Insufficiency before Contrast-enhanced CT by Using Estimated Glomerular Filtration Rates versus Serum Creatinine Level.