Serum creatinine level and renal function in children

Abstract

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.