Parathyroid hormone as a marker for metabolic bone disease of prematurity

Objective:to compare parathyroid hormone to alkaline phosphatase as a serologic marker for metabolic bone disease (mbd) in preterm infants.study design:an 18-month prospective observational study in neonates with birth weight <1250 g. simultaneous serum parathyroid hormone (pth), alkaline phosphatase (alp), calcium (ca) and phosphorus (p) were measured at scheduled intervals during hospitalization. at 6 weeks of age, mbd was evaluated using knee radiographs. comparisons were analyzed using multivariate logistic regression, receiver operating characteristic (roc) curves, χ2 and student t-test.result:fourty-nine infants were included in the study: 7 with severe and 42 with mild mbd. using roc curves, at 660 u l−1 alp had a sensitivity of 29% and specificity of 93% for severe mbd, while a cutoff point of 180 mg dl−1 gave pth a sensitivity of 71% and specificity of 88%. infants with severe bone disease had a lower birth weight, 21-day serum p, an increased use of glucocorticoids and caffeine, and more likely to have major neonatal morbidities.conclusion:pth is an early marker with better sensitivity than alp in screening for mbd. at 3 weeks chronologic age, a pth level >180 mg dl−1 or a p level <4.6 mg dl−1 yielded a sensitivity of 100% and specificity of 94% for severe mbd.