Role of plasma and urinary calcium and phosphorus measurements in early detection of phosphorus deficiency in very low birthweight infants.

AIM: To analyse the role of serum and urinary calcium and phosphorus levels in early detection of mineral deficiency in very low birthweight (VLBW) infants born appropriate (AGA) and small for gestational age (SGA). METHODS: 64 VLBW infants were included in a cohort study and divided into two groups: AGA (n = 30) and SGA infants (n = 34). Then, they were divided according to the presence of radiological signs of metabolic bone disease (MBD): with MBD (n = 21) and without MBD (n = 34). Blood samples and 6 h urine collections were obtained for calcium, phosphorus, alkaline phosphatase activity and creatinine determinations between 3 and 5 wk of life. RESULTS: There were no biochemical differences between AGA and SGA. Higher values of urinary calcium (MBD = 31.9 +/- 20.2, without MBD = 19.8 +/- 15.4; p = 0.017), calciuria (MBD = 2.3 +/- 0.3, without MBD = 1.4 +/- 0.8; p = 0.037) and alkaline phosphatase activity (MBD = 369 +/- 114, without MBD = 310 +/- 93; p = 0.04) were found in infants who developed MBD. Both groups showed high tubular phosphorus reabsorption indicating mineral deficiency. CONCLUSION: Serum calcium and phosphorus levels are not good markers in early detection of mineral deficiency. However, the monitoring of calcium urinary levels may be helpful in early detection of mineral deficiency.

[Critical analysis of pathophysiological, diagnostic and therapeutic aspects of metabolic bone disease in very low birth weight infants] / Análise crítica dos aspectos fisiopatológicos, diagnósticos e terapêuticos da doença metabólica óssea em recém-nascidos de muito baixo peso.

OBJECTIVE: To perform a systematic review on the pathophysiology, diagnosis and approach of metabolic bone disease in very low birth weight infants. SOURCES: Literature review of articles published in Medline within the last twenty years. SUMMARY OF THE FINDINGS: The higher survival of very low birth weight infants was concurrent with the increased incidence of metabolic bone disease. The process of bone mineral acquisition suffers some alterations during the neonatal period, including low bone mineral content at birth, insufficient mineral supply in the neonatal period, and regulatory disorders, which may compromise growth and development on the long run. The diagnosis is based on the association of risk factors, and biochemical and radiological alterations. The early intervention in the neonatal period prevents the development of severe metabolic bone disease, reducing complications during the first year of life. CONCLUSIONS: The early diagnosis of metabolic bone disease allows for early intervention, thus preventing complications that may originate from the alterations in bone mineral acquisition.