Objective: Vitamin D deficiency is estimated to affect one billion people worldwide. In the United States, 9-12%\r\nof healthy children have vitamin D deficiency. Renal calcium and phosphate excretion in healthy people is a sensitive\r\nindicator of total body mineral balance. We explored the possibility of using urine calcium-to-creatinine (Uca/Ucr) and\r\nurine phosphate-to-creatinine (Uphos/Ucr) as noninvasive biomarkers of vitamin D deficiency in at risk children.\r\nPatients and methods: This was an observational study of children with one or more risk factors for vitamin D\r\ndeficiency. Anthropometric data and a physical exam were obtained in all children and skin pigmentation, sunlight\r\nexposure, dietary history, and frequency of vitamin supplementation of both mother and child were determined by\r\nparent report. We measured serum levels of calcium, phosphate, magnesium, intact PTH, 25-hydroxyvitamin D,\r\nalkaline phosphatase, and creatinine.A random urine sample was collected for calcium, phosphate and creatinine.\r\nResults: A total of 60 healthy children were recruited. Mean age of the subjects was 1.4 (range 0.5 to 2.9) years.\r\nTwenty percent of the children were regularly given vitamin D supplements. The prevalence of vitamin D deficiency\r\n(25-hydroxyvitamin D < 50 nmol/L) was 3.4%, vitamin D insufficiency (= 50 and < 80 nmol/L) was 28.6% and vitamin\r\nD sufficiency (= 80 nmol/L) was 68%. One subject had biochemical evidence of rickets. Linear regression analysis\r\nshowed no correlation between 25-hydroxyvitamin D levels and random Uca/Ucr or Uphos/Ucr.\r\nConclusion: Random urine calcium or phosphate levels offer little promise as screening tools for vitamin D\r\ndeficiency in children.
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