Objective: In very preterm infants, there is a high risk for impaired kidney function; therefore, access to normal ranges of glomerular filtration rate (GFR) for age and definition of a reliable normal range of glomerular clearance is essential. Despite this, updated GFR reference values for use in clinical practice are not available. The objective of this study was to determine GFR reference values in very preterm infants aged 27 to 31 weeks' gestation.
Methods: This was a multicenter, prospective cohort study. Infants were recruited to the study before 48 hours of life. Glomerular clearance was measured at inclusion, then weekly for the first month. Reference values were determined by measurement of 12-hour urine specimens and generation of a linear regression model with repeated measures after removal of risk factor components. Validation was checked with a bootstrap technique for infants who were not exposed to significant risk factors.
Results: This study included 275 infants. Median GFR reference values (mL/min per 1.73 m(2)) in infants aged 27 to 31 weeks' gestation ranged from 7.9 to 30.3 on day 7, 10.7 to 33.1 on day 14, 12.5 to 34.9 on day 21, and 15.5 to 37.9 on day 28.
Conclusions: The GFR reference values, presented in this article as 3rd, 10th, 50th, 90th, and 97th percentiles, should be useful in NICUs for adaptation of drug doses to glomerular clearance and in defining infants who present with altered GFR and who need additional investigation and close follow-up to adjust fluid intake and drug dosage.
Trial registration: ClinicalTrials.gov NCT00217191.