Assessment of Glomerular Filtration Rate in Preterm Infants by Serum Creatinine: Comparison With Inulin Clearance

Abstract

Dosage regimens of drugs that are cleared mainly by glomerular filtration as well as fluid management in preterm infants should be based on the glomerular filtration rate (GFR) of the individual patient. However, GFR measurements and collection of urine in newborns are difficult to perform. The 24 to 48 h continuous inulin infusion technique does not require the collection of urine and is considered the most reliable indicator of GFR.1,2 This method is invasive, time-consuming, and expensive. In contrast, serum creatinine measurements can be obtained easily and determined quickly in the clinical chemistry laboratory. Most laboratories use an automated kinetic Jaffé method, which is subject to negative interference by plasma hemoglobin above 0.06 mmol/L, and to negative interference by bilirubin (about 35 µmol/L by a serum bilirubin of about 100 µmol/L).