A reappraisal of the measurement of glomerular filtration rate in pre-term infants.

Thirty-seven single-injection polyfructosan-S (PF-S, Inutest) and 98 continuous-infusion PF-S/creatinine clearance studies were performed in 39 sick very low birth weight infants. The single-injection clearance method for measuring glomerular filtration rate has been shown to be a reliable technique if sampling is continued for 8 h or more and the PF-S (Inutest) assay is sensitive, accurate and precise. The continuous-infusion clearance method is also valid if the infusion is continued for more than 24 h and preceded by a loading dose in the form of a double-rate infusion for 8 h. Creatinine clearance is usually less than PF-S clearance, the mean ratio being 0.91, suggesting that there is some creatinine reabsorption in the renal tubule in sick very low birth weight infants.