Department of Pediatrics, Division of Nephrology, Washington University in St. Louis School of Medicine, 660 Euclid Ave, Campus Box 8116, St. Louis, MO, 63110, USA.
Division of Nephrology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.
Pediatr Nephrol. 2017 Dec;32(12):2311-2318. doi: 10.1007/s00467-017-3730-4. Epub 2017 Jun 30.
Variability in measures of mineral metabolism has not been studied in pediatric end stage kidney disease. We sought to determine the intra-individual variability in measures of mineral metabolism in children on hemodialysis (HD) and its impact on clinical decision-making.
We conducted a prospective single-center study of children (3.6-17.3 years old) on chronic HD. Serial twice weekly measures of serum calcium, phosphate and intact parathyroid hormone (PTH), as well as weekly measures of fibroblast growth factor 23 (FGF23) and vitamin D metabolites, were obtained over a 12-week period in 10 children. Samples (n = 226) were assayed in a single batch at the end of the study.
The median intra-individual coefficient of variation (CV) calculated by 4-week blocks was 5.1-6.5% for calcium, 9.5-14.9% for phosphate and 32.7-33.4% for PTH. The median overall CV for FGF23 was 44.4%. Using the first value of each block as a reference, subsequent values would dictate a discrepant management decision 33-56%, 19-28%, and 30-33% of the time for calcium, phosphate, and PTH, respectively. Adjusting for sex and age, most of the variability in phosphate and PTH was attributable to within-participant variability. For calcium, 49% of the variability was attributable to day of blood collection (Monday vs. Friday). The median (range) of an individual participant's values within clinical target ranges was 55% (26-86%) for calcium, 58% (0-96%) for phosphate, and 21% (0-64%) for PTH.
There is considerable intra-individual variability in measures of mineral metabolism that serve as surrogate markers for bone health in children on HD. Within a 4-week period, at least 20-30% of measures would dictate a discrepant decision from the referent measure of that month. These findings have important implications for clinical decision-making and underscore the need to base therapeutic decisions on trends rather than single measurements.
在儿科终末期肾病患者中，尚未研究矿物质代谢指标的变异性。我们旨在确定血液透析（HD）患儿矿物质代谢指标的个体内变异性及其对临床决策的影响。
我们进行了一项前瞻性单中心研究，纳入了 10 名年龄在 3.6-17.3 岁的慢性 HD 患儿。在 12 周内，每两周采集两次血清钙、磷和全段甲状旁腺激素（iPTH），每周采集一次成纤维细胞生长因子 23（FGF23）和维生素 D 代谢物。在研究结束时，将 226 个样本一次性进行检测。
通过 4 周块计算的个体内变异系数（CV）中位数为钙 5.1-6.5%、磷 9.5-14.9%和 iPTH 32.7-33.4%。FGF23 的总体 CV 中位数为 44.4%。以每个块的第一个值为参考，后续值将导致钙、磷和 iPTH 的管理决策差异分别为 33-56%、19-28%和 30-33%。调整性别和年龄后，磷和 iPTH 的大部分变异性归因于个体内变异。对于钙，49%的变异归因于采血日（周一与周五）。在临床靶标范围内，单个参与者的中位数（范围）值为钙 55%（26-86%）、磷 58%（0-96%）和 iPTH 21%（0-64%）。
HD 患儿的矿物质代谢指标存在相当大的个体内变异性，这些指标是骨骼健康的替代标志物。在 4 周内，至少 20-30%的测量值会导致与当月参考测量值的决策差异。这些发现对临床决策具有重要意义，并强调需要基于趋势而不是单次测量来做出治疗决策。
