NKF K/DOQI GUIDELINES 2000 Several guideline statements refer to
glomerular filtration rates (GFR) below which certain monitoring
strategies or therapies should be instituted. The inulin
clearance is considered to be the most accurate measure of the
GFR. However, it is a laborious and rather expensive
measurement. We describe here recommended methods for
determining GFR that are more useful under clinical conditions.
GFR can be estimated from the serum creatinine concentration and
other factors, or determined more precisely using either timed
urine collections or radioisotope elimination methods.265-267
For the purposes recommended in these guidelines, the estimated
GFR will usually be sufficient to provide a useful "ballpark"
value for the GFR (ie, < 25 mL/min). Direct urinary clearance
measurements will be more useful in determining the degree of
renal dysfunction at lower levels of clearance, when the need
for renal replacement therapy is entertained. The most widely
used method for estimating GFR is the C