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.

Zusammenfassung

Die vorliegende Arbeit überprüft, ob ein 6-Stunden-(6-h-)Sammelurin bei Frühgeborenen die 24-h-Mineralhomöostase vorhersagt. Ca- und P-Konzentrationen wurden im Urin von 60 stabilen Neugeborenen untersucht; Gestationsalter 34 (25-42) Wochen. Bei 58 Kindern wurden vier 6-h-Sammelurine analysiert und bei 2 Kindern jede einzelne Urinportion innerhalb von 24 h. Die Mineralhomöostase der Kinder wurde als Ca- oder P-Überschuss definiert, wenn die Konzentrationen im 24-h-Urin ≥1mmol/l waren. Die Ca- und P-Konzentrationen der 6-h-Proben von 39 Frühgeborenen unterlagen einer starken intraindividuellen Streuung; Variationskoeffizienten: 0,42 (SD 0,26) und 0,41 (SD 0,26). Sensitivität, Spezifität und positiver Voraussagewert (PPV) einer 6-h-Probe für die Erkennung einer Ca-Mangelhomöostase (Ca <1 mmol/l im 24-h-Urin) betrugen 0,93 (0,77-0,98; 95% Konfidenzintervall), 0,72 (0,43-0,90) und 0,9 (0,74-0,96). Die entsprechenden Werte betrugen für P 0,8 (0,38-0,96), 0,97 (0,85-0,995) und 0,8 (0,38-0,96).

Schlussfolgerung:

Bei regelmäßig aller 3-4 h gefütterten Frühgeborenen reicht ein 6-h-Sammelurin aus, um einen Ca- bzw. P-Mangel zu erkennen (PPV 0,92 und 0,83). Regelmäßige Kontrollen (2-mal wöchentlich) werden angeraten, um kein Kind mit einem Mineralmangel zu übersehen.

Key words

infants born preterm - supplementation - calcium - phosphate - monitoring - bone mineral deficiency - osteopenia - urine

Schlüsselwörter

Frühgeborene - Supplementierung - Kalzium - Phosphat - Steuerung - Knochenmineralmangel - Osteopenie

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