The Clinical and Biochemical Predictors of Bone Mass in Preterm Infants

Reference values of parathyroid hormone in very low birth weight infants

PURPOSE

The primary goal was to estimate reference values of parathyroid hormone (PTH) in very low birth weight infants without severe neonatal morbidity. A secondary objective was to assess the relationship between PTH serum levels and selected laboratory markers of bone metabolism.

METHODS

Ninety two infants with birth weight less than 1500 g met the inclusion criteria of the study. Serum levels of PTH, 25-hydroxyvitamin-D [25(OH)D], C3-epi-25(OH)D, total calcium, phosphorus, and alkaline phosphatase, and urinary levels of calcium, phosphorus, and creatinine were examined on day 14 and subsequently every 2 weeks until discharge.

RESULTS

Of the total 167 serum samples examined for PTH levels in infants without 25(OH)D deficiency the estimated range was 0.9-11.9 pmol/l (8.5-112.3 pg/mL). During the first month, no statistically significant correlation was observed between PTH level and that of 25(OH)D, C3-epimers of 25(OH)D, S-Ca, S-P, or ALP, nor with urinary excretion of calcium and phosphorus. From the second month of life, there was a moderately significant correlation between PTH and 25(OH)D (Rho = -0.40, P =< .001), between PTH and calcium/creatinine ratio (Rho = -0.56, P = < .001), and between PTH and phosphorus/creatinine ratio (Rho = 0.51, P = < .001).

CONCLUSIONS

The physiological range for PTH levels for preterm neonates without 25(OH)D deficiency was estimated as 0.9-11.9 pmol/l (8.5-112.3 pg/mL). It seems that elevation of serum PTH above this range can be considered as hyperparathyroidism in very low birth weight infants.

Diagnostics of Metabolic Bone Disease in Extremely Preterm Infants-Clinical Applicability of Bone Turnover Biochemical Markers and Quantitative Ultrasound

BACKGROUND

Significant improvement in neonatal care has enabled increasing survival of preterm infants. Metabolic bone disease of prematurity is often overlooked due to other comorbidities of preterm birth. The best approach is screening and prevention of the disease in high-risk infants such as preterm infants.

AIM

We followed up the clinical, radiological, and serum biochemical markers of metabolic bone disease in extremely preterm infants (<28 weeks of gestation). The clinical applicability and validation of C-terminal telopeptide of type I collagen (CTX-I) as a novel bone turnover marker were assessed. Standard and novel biochemical bone turnover markers and quantitative ultrasound were compared.

METHOD

Patients' data were collected from medical records. Assessments of calcium, phosphate, alkaline phosphatase, bone-alkaline phosphatase, CTX-I, and quantitative ultrasound were prospectively performed twice in 42 extremely preterm infants at postmenstrual ages of 30-32 weeks and 36-40 weeks. Bone mineral density was measured by quantitative ultrasound.

CONCLUSION

Phosphate, alkaline phosphatase, bone alkaline phosphatase, calcium, or ionized calcium are not related to gestational age, but bone mineral density, measured by quantitative ultrasound, is related. There is no correlation between standard and novel biochemical markers and quantitative ultrasound for the identification of metabolic bone disease.

Biomarkers and Biochemical Indicators to Evaluate Bone Metabolism in Preterm Neonates

The purpose of the present study was to evaluate the concentrations of some bone turnover markers in preterm neonates with uncomplicated clinical course in the first month of life. Samples from 13 preterm neonates were collected at three different times: at birth (T0) from umbilical cord blood (UCB); and at 15 (T1) and 30 (T2) days of life from peripheral blood (PB). The concentrations of calcium (Ca), phosphate (P), total alkaline phosphatase (ALP), Collagen Type 1 Amino-terminal Propeptide (PINP), osteocalcin (OC), Collagen Type 1 Carboxyl-Terminal Telopeptide (CTX) and Leptin were assessed. A statistically significant difference for ALP concentration at birth versus T1 and T2 was found. An evident increase in the median concentrations of CTX, OC and PINP from T0 to T2 were observed. A significant difference was also found for Leptin concentration at T0 compared to T1. In preterm infants, in the absence of acute or chronic medical conditions and without risk factors for metabolic bone disease (MBD) of prematurity, there is a significant increase in bone turnover markers during the first month of life. The knowledge of the variations in these markers in the first weeks of life, integrated by the variations in the biochemical indicators of bone metabolism, could help in recognizing any conditions at risk of developing bone diseases.

Prenatal and Neonatal Bone Health: Updated Review on Early Identification of Newborns at High Risk for Osteopenia

Bone health starts with maternal health and nutrition, which influences bone mass and density already in utero. The mechanisms underlying the effect of the intrauterine environment on bone health are partly unknown but certainly include the 'foetal programming' of oxidative stress and endocrine systems, which influence later skeletal growth and development. With this narrative review, we describe the current evidence for identifying patients with risk factors for developing osteopenia, today's management of these populations, and screening and prevention programs based on gestational age, weight, and morbidity. Challenges for bone health prevention include the need for new technologies that are specific and applicable to pregnant women, the foetus, and, later, the newborn. Radiofrequency ultrasound spectrometry (REMS) has proven to be a useful tool in the assessment of bone mineral density (BMD) in pregnant women. Few studies have reported that transmission ultrasound can also be used to assess BMD in newborns. The advantages of this technology in the foetus and newborn are the absence of ionising radiation, ease of use, and, above all, the possibility of performing longitudinal studies from intrauterine to extrauterine life. The use of these technologies already in the intrauterine period could help prevent associated diseases, such as osteoporosis and osteopenia, which are characterised by a reduction in bone mass and degeneration of bone structure and lead to an increased risk of fractures in adulthood with considerable social repercussions for the related direct and indirect costs.

Early elevated alkaline phosphatase as a surrogate biomarker of ongoing metabolic bone disease of prematurity

Very low birth weight (VLBW) neonates present a high risk of metabolic bone disease (MBD). Our main objective was to determine the easiest way to make an early diagnosis of this disease by identifying surrogate biomarkers before any radiological signs occurred. We conducted in our NICU a 6-month observational prospective study, with inclusion of all singleton VLBW neonates. We collected clinical and biological data, and nutritional intakes during hospitalization. We defined biological MBD (bMBD) as alkaline phosphatase (ALP) levels superior to 600 UI/L at day of life 30 (DOL30) and performed a case-control analysis. Nine out of 30 patients (30%) exhibited bMBD. All have extremely low birth weight and were significantly younger in gestational age (GA) and smaller at birth. There was no statistically significant difference in nutritional intake between bMBD and control groups. In the bMBD group, phosphatemia was lower since DOL3. ALP was already significantly higher at DOL15, and way beyond normal range.

CONCLUSIONS

Our results showed that even the strict respect of nutritional guidelines cannot completely prevent bMBD in high-risk patients and suggest that an early screening from DOL15, with ALP levels greater than 500 UI/L, could be sufficient for detection of upcoming MBD.

WHAT IS KNOWN

• Metabolic bone disease of prematurity (MBD) definition is not consensual, but biological changes appear earlier than radiological signs of rickets. • MBD management relies on biological evidence. Treatment is based on phosphate and/or calcium and calcitriol supplementation.

WHAT IS NEW

• Studying phosphocalcic biological assessment in very low birth weight neonates, we showed respect of nutritional guidelines could not protect from biological MBD. • Increase in alkaline phosphatase (ALP), about 500 UI/l at day of life 15, could be a biomarker of MBD with no need of X-ray evaluation and sufficient to begin a treatment to prevent osteopenia.

Relationship of caffeine regimen with osteopenia of prematurity in preterm neonates: a cohort retrospective study

BACKGROUND

Caffeine is a routinely prescribed pharmacological active compound in neonatal intensive care units (NICU) for treating apnea of prematurity (AOP), which also decreases the risk of bronchopulmonary dysplasia and cerebral palsy in neonates. Caffeine-induced excessive calcium loss can promote the development of metabolic bone disease (MBD) in preterm neonates. This study aimed to evaluate the effect of the caffeine regimen on the development of osteopenia of prematurity (OOP), using serum alkaline phosphatase (serum-ALP) concentrations as a surrogate marker at the 4^th week of life.

METHODS

This retrospective cohort study was conducted including neonates of < 32 weeks gestational age (GA) and birth weight < 1500 g, admitted to NICU from April-2017 to December-2018 and received caffeine therapy till 28 days of life for AOP. Based on serum-ALP levels, formed the high and low-ALP groups. Neonatal characteristics, caffeine regimen, risk factors for OOP, including duration of parenteral nutrition (PN), exposure to medicines associated with MBD, and intake of essential vitamins and minerals, were compared in both groups. Predictors of OOP were analyzed through logistic regression.

RESULTS

From the total of 268 participants, 52 (19%) developed OOP, mostly female (61.5%). In the high ALP group, the serum-ALP levels were significantly higher than in the low-ALP group (725.0 ± 143.8 vs 273.6 ± 55.0 units/L, p < 0.001). The high-ALP group received significantly (p < 0.001) higher daily and cumulative caffeine doses and were associated with a higher likelihood of developing OOP in this study cohort [cumulative dose (mg) (AOR = 1.082 95% CI 1.011 to 1.157) and daily dose (mg/kg/day) (AOR = 2.892 95% CI 1.392 to 6.007)]. Smaller GA was found directly related to OOP. Among the other medical risk factors, phosphorus intake was significantly low in the high-ALP group. No, significant relationship between duration of PN and use of steroids and diuretics, and intake of vitamins and minerals were identified.

CONCLUSION

The daily and cumulative doses of caffeine and smaller GA are associated with the development of OOP in this study cohort. Clinical randomized control studies are needed to validate the outcomes and determine the range of safest and most effective caffeine doses for treating AOP in preterm neonates.

The incidence of osteopenia of prematurity in preterm infants without phosphate supplementation: A prospective, observational study

To meet their requirements for bone mineralization, it is recommended that preterm infants receive nutritional support containing calcium and phosphate. There are no clear data on the incidence of osteopenia of prematurity (OFP) in preterm infants without phosphate supplementation.This study aimed to investigate the incidence of OFP in preterm infants without phosphate supplementation and its relationship with the duration of parenteral nutrition (PN).This was a prospective and observational study.This study included 30 infants aged <32 gestational weeks and weighed <1500 g at birth. All infants received PN according to a standard protocol, beginning on day 1 with calcium, without phosphate. Starting from the first day of life, all infants received human milk without fortifiers. Oral vitamin D (400 IU/d) was administered when enteral nutrition reached 100 mL/kg/d.The diagnosis of OFP was based on radiographs that were taken of both wrists. Serum alkaline phosphatase (ALP) was measured 3 times: at the start of PN (ALP 1), at the end of PN (ALP 2), and at discharge or the expected due date (ALP 3). Radiographs were obtained on the same day as ALP 3. The duration of PN was analyzed in the presence of OFP using receiver operating characteristic curve analysis.Among the 30 infants, 13 (43%) were diagnosed with OFP. The duration of PN was significantly longer in the OFP group than in the group without OFP (16 vs 12 days; P < .05). The provision of PN for >15 days significantly increased the risk of OFP (odds ratio, 5.40; 95% confidence interval, 1.12-26.04; P = .035).We found a high incidence of OFP in preterm infants without phosphate supplementation. An association was found between the duration of PN and the incidence of OFP. Further research is needed to prevent the development of osteopenia in preterm infants.

Convolutional Neural Network-Based Humerus Segmentation and Application to Bone Mineral Density Estimation from Chest X-ray Images of Critical Infants

Measuring bone mineral density (BMD) is important for surveying osteopenia in premature infants. However, the clinical availability of dual-energy X-ray absorptiometry (DEXA) for standard BMD measurement is very limited, and it is not a practical technique for critically premature infants. Developing alternative approaches for DEXA might improve clinical care for bone health. This study aimed to measure the BMD of premature infants via routine chest X-rays in the intensive care unit. A convolutional neural network (CNN) for humeral segmentation and quantification of BMD with calibration phantoms (QRM-DEXA) and soft tissue correction were developed. There were 210 X-rays of premature infants evaluated by this system, with an average Dice similarity coefficient value of 97.81% for humeral segmentation. The estimated humerus BMDs (g/cm³; mean ± standard) were 0.32 ± 0.06, 0.37 ± 0.06, and 0.32 ± 0.09, respectively, for the upper, middle, and bottom parts of the left humerus for the enrolled infants. To our knowledge, this is the first pilot study to apply a CNN model to humerus segmentation and to measure BMD in preterm infants. These preliminary results may accelerate the progress of BMD research in critical medicine and assist with nutritional care in premature infants.

Body composition and neuromotor development in the year after NICU discharge in premature infants

BACKGROUND

Hypothesis: neuromotor development correlates to body composition over the first year of life in prematurely born infants and can be influenced by enhancing motor activity.

METHODS

Forty-six female and 53 male infants [27 ± 1.8 (sd) weeks] randomized to comparison or exercise group (caregiver provided 15-20 min daily of developmentally appropriate motor activities) completed the year-long study. Body composition [lean body and fat mass (LBM, FM)], growth/inflammation predictive biomarkers, and Alberta Infant Motor Scale (AIMS) were assessed.

RESULTS

AIMS at 1 year correlated with LBM (r = 0.32, p < 0.001) in the whole cohort. However, there was no effect of the intervention. LBM increased by ~3685 g (p < 0.001)); insulin-like growth factor-1 (IGF-1) was correlated with LBM (r = 0.36, p = 0.002). IL-1RA (an inflammatory biomarker) decreased (-75%, p < 0.0125). LBM and bone mineral density were significantly lower and IGF-1 higher in the females at 1 year.

CONCLUSIONS

We found an association between neuromotor development and LBM suggesting that motor activity may influence LBM. Our particular intervention was ineffective. Whether activities provided largely by caregivers to enhance motor activity in prematurely born infants can affect the interrelated (1) balance of growth and inflammation mediators, (2) neuromotor development, (3) sexual dimorphism, and/or (4) body composition early in life remains unknown.

Do preterm bones still break? Incidence of rib fracture and osteopenia of prematurity in very low birth weight infants

AIM

Extremely premature babies are at risk of osteopenia of prematurity (OOP) as bone mineralisation in utero increases exponentially after 24 weeks gestation. Our aim was to assess the bone health of very low birth weight (VLBW) infants. We wanted to establish the incidences of OOP and rib fracture. We also looked at which biochemical markers best predicted OOP. Bone health in this vulnerable population is an important aspect of management which should not be overlooked.

METHODS

This was an observational study which included all VLBW infants, born in a national maternity hospital, over a 5-year period. All X-rays performed on these infants were reviewed. Data were also collected on biochemical markers associated with bone health. The medical records of infants with rib fractures were reviewed looking for causes of bone fragility.

RESULTS

Of the 609 VLBW infants included in the study, only two cases of definitive rib fractures were found. This represents a rib fracture incidence of 3 per 1000. Thirty-nine percent of VLBW babies showed radiological evidence suggestive of OOP.

CONCLUSION

Our findings show a lower rate of rib fracture in preterm infants compared to previous evidence. We also showed that these fractures were not evident on the final X-ray prior to discharge. This implies that when an ex-preterm infant presents to the emergency department with a rib fracture there should be an even higher suspicion for non-accidental injury than previously thought.

Mineral and nutritional requirements of preterm infant

Preterm infants are at risk of growth failure and metabolic bone disease due to insufficient nutrient supply in postnatal life. An ample provision of protein, energy, calcium and phosphates through parenteral or/and enteral nutrition is crucial for bone growth and mineralization. Additional vitamin D supplementation improves bone mineralization and enhance intestinal absorption of minerals.

Screening for Metabolic Bone Disease of prematurity

Metabolic bone disease (MBD) of prematurity remains a significant comorbid condition in preterm, low birth weight infants. As the majority of in utero calcium (Ca) and phosphorus (Phos) accretion occurs during the third trimester, many of these children have inadequate mineral stores and are at risk for deficiencies of Ca and Phos. While fortification of formula has allowed for increased mineral delivery to premature infants, intestinal immaturity prevents optimal absorption. This is compounded by immobilization, delayed establishment of enteral feeds, long term parenteral nutrition and medications that may alter mineral levels. Over time, biochemical changes occur and accompany MBD, with poor bone mineralization during this period increasing the risk for complications such as osteopenia, rickets and fractures. Screening is largely based on risk factors, but despite the 2013 AAP Consensus Statement, there remains significant variation in screening practices across institutions. A combination of laboratory and radiologic testing is often used to diagnose and manage MBD of prematurity, but there exists a lack of consensus on which screening tests and thresholds to use. This is in part related to a lack of normative data and clinical trials for preterm infants, and a result, a lack of evidence-based guidelines on the diagnosis and timing of potential treatment. Biochemical markers, such as serum Phos, alkaline phosphatase (ALP) and parathyroid hormone (PTH), have shown some benefit in the diagnosis of MBD in some studies, but have not always been reproducible. Radiographs may identify different degrees of skeletal changes, but these changes may not be detected until later in MBD development. Other modalities, such as DXA and ultrasound, have also been used, but these may be limited by lack of standards in preterm infants or lack of availability in some centers. Further research, more specifically clinical trials, are needed to determine which combination of tests can detect MBD at its earliest, in order to promote early treatment and prevent short- and long-term complications of MBD.

Metabolic bone disease of prematurity: causes, recognition, prevention, treatment and long-term consequences

Metabolic bone disease of prematurity (MBDP) is characterised by skeletal demineralisation, and in severe cases it can result in fragility fractures of long bones and ribs during routine handling. MBDP arises from prenatal and postnatal factors. Infants who are born preterm are deprived of fetal mineral accumulation, 80% of which occurs in the third trimester. Postnatally, it is difficult to maintain a comparable intake of minerals, and medications, such as corticosteroids and diuretic therapy, lead to bone resorption. With improvements in neonatal care and nutrition, the incidence of MBDP in preterm infants appears to have decreased, although the recent practice of administering phosphate supplements alone will result in secondary hyperparathyroidism and associated bone loss, worsening MBDP. Postnatal immobilisation and loss of placental supply of oestrogen also contribute to skeletal demineralisation. There is no single diagnostic or screening test for MBDP, with pitfalls existing for most radiological and biochemical investigations. By reviewing the pathophysiology of calcium and phosphate homeostasis, one can establish that plasma parathyroid hormone is important in determining the aetiology of MBDP - primarily calcipaenia or phosphopaenia. This will then direct treatment with the appropriate supplements while considering optimal physiological calcium to phosphate ratios.

Metabolic Bone Disease of Prematurity: Diagnosis and Management

Metabolic Bone Disease (MBD) of prematurity is a multifactorial disorder commonly observed in very low birth weight (VLBW, <1,500 g) newborns, with a greater incidence in those extremely low birth weight (ELBW, <1,000 g). MBD is characterized by biochemical and radiological findings related to bone demineralization. Several antenatal and postnatal risk factors have been associated to MBD of prematurity, although the main pathogenetic mechanism is represented by the reduced placental transfer of calcium and phosphate related to preterm birth. The diagnosis of MBD of prematurity requires the assessment of several biochemical markers, radiological, and ultrasonographic findings. However, the best approach is the prevention of the symptomatic disease, based on the screening of subjects exposed to the risks of developing MBD. Regarding the subjects who need to be screened, there is a substantial agreement on the potential risk factors for MBD. On the contrary, different recommendations exist on the diagnosis, management and treatment of this disorder of bone metabolism. This review was aimed at: (1) identifying the subjects at risk for MBD of prematurity; (2) indicating the biochemical findings to take in consideration for the prevention of MBD of prematurity; (3) suggesting practical recommendations on nutritional intake and supplementation in these subjects. We searched for papers which report the current recommendations for biochemical assessment of MBD of prematurity and for its prevention and treatment. The majority of the authors suggest that MBD of prematurity is a disease which tends to normalize overtime, thus it is not mandatory to mimic the rate of mineral fetal accretion through parenteral or enteral supplementation. The optimization of total parenteral nutrition (TPN) and the early achievement of a full enteral feeding are important goals for the prevention and management of MBD of prematurity.

Incidence of metabolic bone disease in preterm infants of birth weight <1250 g and in those suffering from bronchopulmonary dysplasia

BACKGROUND & AIMS

Preterm infants are exposed to a higher risk of developing Metabolic Bone Disease (MBD) with an increased bone fragility, a higher fracture risk and a long-term reduced linear growth and childhood height. Monitoring bone growth has become mandatory in neonatology. Several risk factors have been identified among the population of extremely low birth weight infants, but we still do not know which is the real incidence of MBD since its evaluation is not routinely performed worldwide. The aim of this study was to evaluate the incidence of MBD in preterm infants and in those suffering from bronchopulmonary dysplasia (BPD).

METHODS

Prospective evaluation of patients who developed BPD (BPD group) versus infants who did not develop it (no-BPD group). We examined, in preterms <1.250 g, the metacarpus bone transmission time (mc-BTT) at birth, 21 days and 36 weeks of gestational age (GA) together with biochemical markers of bone status.

RESULTS

We included 135 patients, 55 with BPD. BPD patients received less total proteins in the first two weeks and less energy in the first month of life (p = 0.007 and p < 0.001 respectively). BPD patients had a worse growth velocity at two weeks of age (12.36 ± 7.86 vs 16.59 ± 7.05 g/kg/day, p = 0.001). At 21 days, BPD patients had lower phosphatemia (1.65 ± 0.031 mmol/L vs 1.85 ± 0.034 mmol/L, p = 0.007) and higher alkaline phosphatase levels (411.62 ± 135.31 IU/l vs 338.98 ± 102.20 IU/l, p = 0.005). BPD patients had significantly worse mc-BTT at 36 weeks GA (0.45 ± 0.06 vs 0.50 ± 0.08 μsec, p < 0.001) and a higher incidence of MBD (60% vs 34%; p = 0.012).

CONCLUSIONS

BPD infants are a special subset of patients among preterms who receive, in the first month of life, a lower energy intake than patients without BPD. BPD patients have a suboptimal bone growth and a higher incidence of MBD. Monitoring growth, bone status and optimizing nutritional intakes need to be further improved in preterm infants with BPD.

Risk factors of metabolic bone disease of prematurity

OBJECTIVE

To identify the factors that increase risk of metabolic bone disease of prematurity (MBD).

STUDY DESIGN

A retrospective case-control study of infants born between January 2013-April 2014 with gestation age <30weeks and birth weight <1000g. MBD was defined as serum alkaline phosphatase above 500U/L and characteristic radiographic changes. Information was obtained on the presence of specific comorbidities.

RESULTS

Of 76 infants evaluated, 40 met criteria for MBD. Median gestational age was 25weeks in both groups (p=0.512). Median birth weight of infants with MBD was significantly lower than that of controls (560 vs. 765g, p<0.01). Longer period of parenteral nutrition and dexamethasone use was observed in MBD group. Cholestasis was associated with the highest likelihood of MBD (OR 16.6, 95% CI 4.8-56.9). Seizures (OR 5.2, 95% CI 1.3-20.5) and the prolonged use of diuretics (OR 2.6, 95% CI 1.0-7.0) also significantly increased the likelihood of MBD. Only cholestasis remained significant (OR 9.6, 95% CI 2.1-45.3) after multiple regression analysis.

CONCLUSION

Cholestasis is a significant risk factor for the development of MBD. Our future studies will be directed towards determining the causal relationship between cholestasis and MBD.