Urinary excretion of pyridinium crosslinks and N-terminal crosslinked peptide in preterm and term infants

Urinary excretion of pyridinium crosslinks of collagen, pyridinoline, deoxypyridinoline, and N-terminal crosslinked peptide are now widely used as biochemical markers of bone resorption. In the present cross-sectional study we measured the urinary excretion of total pyridinoline and total deoxypyridinoline by HPLC and N-terminal crosslinked peptide by ELISA in 43 preterm and term newborns in the first 2 months of life. The infants had no history of endocrine or metabolic diseases, bone, chronic heart, or pulmonary diseases. The results were compared by parametric covariance analysis, the HPLC and ELISA results by the Bland-Altman plot. Preterm infants had a statistically higher level of pyridinium crosslinks and N-terminal crosslinked peptide in urine (P < 0.05) than term infants. The very low birthweight infants (gestational age 26-32 weeks) had the highest levels of pyridinoline, deoxypyridinoline and N-terminal crosslinked peptide. Levels of both pyridinium crosslinks and N-terminal crosslinked peptide were independent of sex (P > 0.05). The Bland-Altman plot showed a good agreement between the levels of pyridinium crosslinks and N-terminal crosslinked peptide. Measurement of pyridinium crosslinks and N-terminal crosslinked peptide excretion in small infants gives information about skeletal growth and individual bone turnover, which is dependent on gestational age and birthweight. HPLC and ELISA are reliable methods for the measurement of pyridinium crosslinks and N-terminal crosslinked peptide, respectively.