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Anthropometric determinants of creatinine excretion in preterm infants
Insights
Urinary creatinine output increases with body weight in preterm infants, mirroring protein content changes. This finding establishes creatinine as a valuable indicator for monitoring infant growth and development.
Area of Science:
- Biochemistry
- Pediatrics
- Neonatology
Background:
- Creatinine output per body weight unit rises during childhood, linked to increasing muscle mass.
- Established creatinine excretion values are lacking for preterm infants, hindering growth assessment.
Purpose of the Study:
- To establish standard urinary creatinine excretion values for preterm infants.
- To determine the relationship between creatinine output and infant growth parameters.
- To evaluate creatinine output as a potential biomarker for preterm infant growth.
Main Methods:
- Collected 24-hour urine samples from 15 preterm infants (26-33 weeks gestational age) in their second week of life.
- Measured urinary creatinine output and correlated it with birth weight, length, and gestational age.
- Utilized regression analysis, including stepwise regression, to identify the best predictors of creatinine excretion.
Main Results:
- Developed three significant regression equations relating creatinine excretion to birth weight, length, and gestational age.
- Creatinine output showed the strongest correlation with birth weight.
- Creatinine output per kilogram increased by 16% for infants between 0.7 kg and 1.5 kg birth weight.
Conclusions:
- Urinary creatinine output in preterm infants is a reliable indicator of growth.
- The observed increase in creatinine output parallels changes in body protein content.
- Creatinine excretion serves as a valuable tool for monitoring growth in preterm neonates.
Abstract:
Creatinine output per unit of body weight increases throughout childhood. this reflects the increase in percent muscle mass observed during growth. Standard values for creatinine excretion are not available for the preterm infant. Accordingly, urinary creatinine output was measured in timed 24-hour specimens obtained in the second week of life of 15 preterm infants (gestational age 26 to 33 weeks). Three highly significant regression equations were derived that relate creatinine excretion to birth weight, length, and gestational age. Creatinine output correlated best with birth weight. Stepwise regression yielded no linear combination of these variables that improved the estimate based on weight alone. In a similar manner, consideration of other variables, including weight and length for age (expressed as percent of 50th percentile), did not improve the estimate based on weight alone. These data demonstrate that creatinine output in milligrams per kilogram of body weight increases by 16% between birth weight of 0.7 and 1.5 kg. This increase parallels that in body protein content per kilogram obtained from published fetal body composition data in infants of similar age. Creatinine output in preterm infants, therefore, can serve as a measure of growth.