Calcium and Phosphor Intake in Preterm Infants: Sensitivity and Specifity of 6-Hour Urine Samples to Detect Deficiency
ABSTRACT Aim of the present study was to test whether six-hour (6 h) urine specimens predict the 24-hour (24 h) mineral homeostasis in individual infants born preterm. Urinary Calcium (Ca) and Phosphate (P) concentrations were studied in 60 stable infants; gestational age 34 (25-42) weeks. In 58 infants four 6 h urine specimens and in 2 infants all spot urine specimens obtained within 24 h were analyzed. In 39 infants born preterm coefficients of variation were 0.42 (SD 0.26) and 0.41 (SD 0.26) for Ca and P measurements in the four 6 h urine specimens obtained within 24 h, respectively, The mineral homeostasis of the infants was defined as Ca or P surplus homeostasis if the 24 h urinary concentrations were ≥1 mmol/l. The sensitivity, specificity, and PPV of a 6 h urinary specimen to predict Ca deficiency homeostasis (24 h urinary Ca <1 mmol/l) were 0.93 (0.77-0.98; 95%CI), 0.72 (0.43-0.90) and 0.90 (0.74-0.96). The sensitivity, specificity and PPV for urinary P were 0.8 (0.38-0.96), 0.97 (0.85-0.995), and 0.8 (0.38-0.96). In conclusion, in infants born preterm on regular 3 or 4 h feedings, 6 h urine sampling is sufficiently precise for prediction of Ca and P mineral deficiency homeostasis (PPV 0.92 and 0.83). However, measurements at regular intervals (twice weekly) are recommended not to miss any infant in mineral deficiency homeostasis.
- Klinische Pädiatrie 03/2012; 224(2):51-2. DOI:10.1055/s-0032-1306351 · 1.90 Impact Factor
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ABSTRACT: Bone mineral deficiency of prematurity (BMDoP) is caused by the lack of simultaneous availability of calcium (Ca) and anorganic phosphate (P) during rapid skeletal growth. Review of the literature on the prevention of BMDoP, with specific attention to the limitations of the monitoring of urinary calcium and phosphate concentrations. Intrauterine bone mineral accretion (BMA) can be achieved in preterm infants if urinary concentrations of Ca and P continuously show that the supplementation with these ions slightly exceeds the actual need. An individually adjusted supplementation with Ca and P appears rational because both growth velocity and enteral Ca absorption are highly variable and determine the need for enteral Ca and P administration. If, however, urinary concentrations of Ca and P are used to determine whether Ca and P supplementation is adequate, mechanisms affecting the urinary excretion of these ions other than nutrition have to be taken into account. Specifically, methylxanthines and diuretics increase the renal Ca losses, and the renal P threshold may be lowered in premature infants. A positive effect of physical activity on BMA has been shown in several studies. An individualized Ca and P supplementation in preterm infants aiming for supplementation in a slight excess of the actual need and guided by urinary Ca and P concentrations appears able to prevent BMDoP. Monitoring of urinary Ca and P concentrations needs to take into account non-nutritional factors affecting these concentrations. BMA may further be improved by physical activity.Klinische Pädiatrie 03/2012; 224(2):80-7. DOI:10.1055/s-0031-1295422 · 1.90 Impact Factor
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ABSTRACT: Current concepts on zinc requirements for premature infants rely on studies dating back more than 20 years. Given that nowadays more premature infants frequently survive we aimed to obtain recent frequency data on zinc deficiency in very low birth weight (VLBW) infants.226 VLBW infants born between July 2005 and December 2009 were retrospectively included in this study. Mean gestational age (GA) was 28.7 weeks (range 23+0 to 38+0) and mean birth weight 1120g (range 354-1495). All infants received zinc supplementation according to the ESPGHAN guidelines. 26 (11.5%) patients showed clinical signs for zinc deficiency of whom 15 had serum zinc concentrations < 50µg/dl, 9 between 50 and 70 µg/dl and 2 > 70 µg/dl. Infants presenting with dermatitis had significantly lower concentrations (mean 26.7 µg/dl, range 19-31) when compared to infants with diarrhoea or isolated peripheral oedema (35.3 µg/dl and 51.8 µg/dl respectively). Strongest independent risk factors were low GA, being small for GA and suffering from intestinal resection due to necrotizing enterocolitis. Frequency of zinc concentrations <50 µg/dl were calculated to be 6.6% in VLBW infants.Even though current guidelines for zinc supplementation were followed the frequency of zinc deficiency was found to be unexpectedly high in ELBW and SGA infants. Despite the retrospective nature of this single centre study, our data strongly suggest that recommendations on zinc supplementation in ELBW and SGA infants should be reviewed.Klinische Pädiatrie 07/2012; 225(1). DOI:10.1055/s-0032-1312610 · 1.90 Impact Factor