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


CONCLUSIONS
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.
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Department of Pediatrics, Nursery Annex to Maternity Ward, Children's Institute, Clinics Hospital, School of Medicine University of São Paulo, SP, Brazil. bmancini@terra.com.br
Leone
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D000469:Alkaline Phosphatase / Q000097:blood / Q000652:urine; D001851:Bone Diseases, Metabolic / Q000209:etiology; D002118:Calcium / Q000097:blood* / Q000652:urine*; D015331:Cohort Studies; D003401:Creatine / Q000097:blood / Q000652:urine; D006801:Humans; D017674:Hypophosphatemia / Q000097:blood* / Q000150:complications / Q000652:urine*; D007231:Infant, Newborn; D007234:Infant, Premature; D019102:Infant, Very Low Birth Weight; D010758:Phosphorus / Q000097:blood* / Q000652:urine*; D011446:Prospective Studies
D010758:Phosphorus; D000469:Alkaline Phosphatase; D003401:Creatine; D002118:Calcium