Serum creatinine level and renal function in children
J. E. Springate, S. L. Christensen and L. G. Feld
Division of Nephrology, Children's Hospital of Buffalo, NY.
OBJECTIVE--To evaluate the accuracy of serum creatinine and height/serum
creatinine glomerular filtration rate (Cr-GFR) formula as screening tests
for abnormal renal function defined by plasma
diethylenetriaminepenta-acetic acid (DTPA) clearance. DESIGN--Patient
series. SETTING--The Children's Hospital of Buffalo (NY).
PATIENTS--Eighty-seven consecutive patients ranging in age from 2 to 20
years. MEASUREMENTS--The Cr-GFR was calculated by means of the formula GFR
(milliliters per minute per 1.73 m2) = kL/serum creatinine (milligrams per
deciliter), where L is body length in centimeters and k is a constant
dependent on age and sex. Plasma clearance of technetium Tc 99m-labeled
DTPA was our reference method for determination of GFR (DTPA-GFR).
RESULTS--The Cr-GFR formula identified children with impaired renal
function (DTPA clearance, less than 80 mL/min per 1.73 m2) with a
sensitivity of 95% and a specificity of 93%. In contrast, the sensitivity
and specificity of elevated serum creatinine level for this purpose were
80% and 96%, respectively. Of the children with renal insufficiency (DTPA
clearance, 40 to 79 mL/min per 1.73 m2), 91% were correctly identified by
the Cr-GFR formula. However, only 65% of these children had elevated serum
creatinine levels. Although all children with renal failure (DTPA
clearance, less than 40 mL/min per 1.73 m2) had abnormally high serum
creatinine levels, the specificity of this test was significantly lower
than that of the Cr-GFR formula (75% vs 100%, respectively).
CONCLUSIONS--The Cr-GFR formula is superior to serum creatinine level for
estimating GFR. This formula provides a simple, reasonably accurate
screening test for the presence and severity of impaired renal function.
