Role of fibroblast growth factor-23 as an early marker of metabolic bone disease of prematurity.

PURPOSE: Metabolic bone disease of prematurity (MBDP) remains a significant cause of morbidity in extremely premature newborns. In high-risk patients, suspected diagnosis and subsequent treatment modifications, with limitations in terms of sensitivity and specificity, rely on low phosphorus levels and/or high levels of alkaline phosphatase (ALP). We investigated the potential of fibroblast growth factor-23 (FGF23) as an early marker for MBDP when measured at 3-4 weeks of life in at-risk patients. METHODS: A single-center prospective observational non-interventional study including preterm newborns of both sexes, with a gestational age of less than 32 weeks and/or a birth weight of less than 1500 g. In the standard biochemical screening for MBDP performed between 3 and 4 weeks of life within a nutritional profile, the determination of FGF23 was included along with other clinical and metabolic studies. The study was conducted at Marqués de Valdecilla University Hospital in Santander, Spain, from April 2020 to March 2021. Participants provided informed consent. Biochemical analyses were conducted using various platforms, and follow-up evaluations were performed at the discretion of neonatologists. Patients at high risk for MBDP received modifications in treatment accordingly. The sample was descriptively analyzed, presenting measures of central tendency and dispersion for continuous variables, and absolute numbers/percentages for categorical ones. Tests used included t-tests, Mann‒Whitney U tests, chi-square tests, logistic regressions, Pearson correlation, and ROC curve analysis (IBM SPSS Statistics version 19). Significance level: P < 0.05. RESULTS: In the study involving 25 at-risk premature newborns, it was found that 20% (n = 5) were diagnosed with MBDP. Three of these patients (60%) were identified as high-risk based on standard biochemical evaluation at 3-4 weeks of age, while the other two patients (40%) were diagnosed in subsequent weeks. However, in all 5 patients, measurement of FGF23 levels would allow for early identification and optimization of treatment before other markers become altered. Low levels of FGF23 at 3-4 weeks, even with normal phosphorus and ALP levels, indicate the need for modifications in nutritional supplementation. CONCLUSIONS: MBDP remains a significant concern in extremely premature newborns. Current diagnostic methods rely on limited biochemical markers. Early detection of low FGF23 levels enables timely interventions, potentially averting demineralization.

Mild Hypophosphatemia-Associated Conditions in Children: The Need for a Comprehensive Approach.

To better understand the causes of hypophosphatemia in children, we evaluated all serum phosphate tests performed in a tertiary hospital with unexpected but persistent temporary or isolated hypophosphatemia over an 18 year period. We collected 29,279 phosphate tests from 21,398 patients, of which 268 (1.2%) had at least one result showing hypophosphatemia. We found that endocrinopathies (n = 60), tumors (n = 10), and vitamin D deficiency (n = 3) were the medical conditions most commonly associated with mild hypophosphatemia, but in many patients the cause was unclear. Among patients with endocrinopathies, those with diabetes mellitus were found to have lower mean serum phosphate levels (mean 3.4 mg/dL) than those with short stature (3.7 mg/dL) or thyroid disorders (3.7 mg/dL). In addition, we found a correlation between glycemia and phosphatemia in patients with diabetes. However, despite the potential relevance of monitoring phosphate homeostasis and the underlying etiologic mechanisms, renal phosphate losses were estimated in less than 5% of patients with hypophosphatemia. In the pediatric age group, malignancies, hypovitaminosis D, and endocrine disorders, mostly diabetes, were the most common causes of hypophosphatemia. This real-world study also shows that hypophosphatemia is frequently neglected and inadequately evaluated by pediatricians, which emphasizes the need for more education and awareness about this condition to prevent its potentially deleterious consequences.

Modified Serum ALP Values and Timing of Apparition of Knee Epiphyseal Ossification Centers in Preterm Infants with Cholestasis and Risk of Concomitant Metabolic Bone Disease of Prematurity.

The usefulness of serum alkaline phosphatase (ALP) and phosphorous in screening and monitoring of metabolic bone disease of prematurity (MBDP) still has some limitations, especially in preterm infants with concomitant conditions such as cholestasis. We aimed to assess a modification of serum ALP (M-ALP) as a biomarker for MBDP in preterm infants, and the use of ultrasound monitoring for the apparition of knee ossification centers as marker of bone mineralization. Biochemical and clinical registers were taken from 94 preterm newborns <32 weeks. A significant correlation existed between serum ALP and direct bilirubin (DB), expressed by the regression equation: M-ALP (IU/L) = 302.1 + 96.9 (DB (mg/dL)). The ratio ALP/M-ALP > 1 was demonstrated to be more specific (87.5%) in the diagnosis of MBDP than the cut-off value of serum ALP > 500 IU/L (62.5%). ALP/M-ALP > 1 showed 100% sensitivity and specificity for the diagnosis of MBDP, and a good correlation with specific bone ALP (B-ALP). Patients with the knee nucleus by post-menstrual week 37 had lower B-ALP compared to patients with no nucleus, and no patients with MBDP presented the nucleus by the 40th week. In the absence of reliable specific B-ALP, reinterpreting serum ALP values by M-ALP plus monitoring of knee ossification centers contribute to better management of MBDP in preterm infants with cholestasis.

Markers of inflammation before and during peritoneal dialysis.

In this study, we compared changes in inflammatory markers-C-reactive protein (CRP), pentraxin 3 (PTX3), serum component of amyloid A (SAA), and procalcitonin (PCT)-in 182 subjects: 69 from the general population (GP), 47 with CKD, 19 with an implanted intra-abdominal catheter for peritoneal dialysis ("prePD"), and 47 on peritoneal dialysis (PD). These were the results [median (95% confidence interval)] for the GP CKD, prePD, and PD groups respectively: CRP: 1.40 mg/L (1.15-2.10 mg/L), 5.30 mg/L (3.04-8.06 mg/L), 3.33 mg/L (2.15-12.58 mg/L), 7.25 mg/L (4.43-15.16 mg/L). SAA: 3.10 mg/L (2.90-3.53 mg/L), 7.77 mg/L (4.17-15.83 mg/L), 7.30 mg/L (4.81-10.96 mg/L), 9.14 mg/L (5.31-23.54 mg/L). PCT: 0.028 ng/mL (0.022-0.032 ng/mL), 0.121 ng/mL (0.094-0.166 ng/mL), 0.160 ng/mL (0.090-0.277 ng/mL), 0.363 ng/mL (0.222-0.481 ng/mL). PTX3: 0.54 ng/mL (0.33-0.62 ng/mL), 0.71 ng/ mL (0.32-1.50 ng/mL), 0.56 ng/mL (0.44-1.00 ng/ mL), 1.04 ng/mL (0.65-1.56 ng/mL). After catheter insertion, CRP showed a nonsignificant declining trend that disappeared throughout PD. The behavior of SAA was similar to that of CRP and was not modified by the changes induced by the start of PD. An increase in PTX3 was observed only with PD, which may be related to a local proinflammatory state caused by PD solution. We can conclude that catheter insertion for PD does not account for most of the local inflammatory changes observed in PD patients.

Inflammation markers, chronic kidney disease, and renal replacement therapy.

Chronic kidney disease (CKD) is associated with a proinflammatory state and an excess of cardiovascular risk. In this work, we describe changes in inflammatory markers-C-reactive protein (CRP), pentraxin 3 (PTX3), serum component of amyloid A (SAA), and procalcitonin (PCT)--in CKD patients compared with a control group of subjects with a normal estimated glomerular filtration rate (eGFR). Blood samples were obtained from 69 healthy individuals (GP) and 70 end-stage CKD patients--25 not yet on dialysis, 22 on peritoneal dialysis (PD), and 23 on hemodialysis (HD). These were the results [median (95% confidence interval)] for the GP CKD, PD, and HD groups respectively: CRP: 1.40 mg/L (1.19-2.11 mg/L), 6.50 mg/L (3.57-8.32mg/L), 7.60 mg/L (2.19-22.10mg/L), 9.60 mg/L (6.62-16.38 mg/L). SAA: 3.10 mg/L (2.90-3.53 mg/L), 7.11 mg/L (3.81-15.40mg/L), 9.69 mg/L (5.07-29.47mg/L), 15.90 mg/L (6.80-37.48 mg/L). PCT: 0.03 ng/mL (0.02-0.03 ng/mL), 0.12 ng/mL (0.09-0.16 ng/mL), 0.32 ng/mL (0.20-0.46 ng/ mL), 0.79 ng/mL (0.45-0.99 ng/mL). PTX3: 0.54 ng/mL (0.33-0.62 ng/mL), 0.71 ng/ mL (0.32-1.50 ng/mL), 1.52 ng/mL (0.65-2.13 ng/mL), 1.67 ng/mL (1.05-2.27 ng/mL). Compared with levels in the GP group, levels of SAA and CRP (systemic response) were significantly higher in CKD patients on and not on dialysis. Levels of PTX3 were higher only in dialyzed patients, significantly so in those on HD (greatly different from the CRP levels). These differing levels might be related to a local reaction caused by an invasive intervention (PD or HD). As eGFR declines and with the start of renal replacement therapy, PCT increases. Levels of PCT could potentially cause confusion when these patients are being evaluated for the presence of infection, and may also demonstrate some microvascular implications of dialysis therapy.