Trabecular Bone Score in Children and Adolescents With Inflammatory Bowel Diseases

Trabecular Bone Score in Assessing Bone Mineralization Status in Children with End- Stage Renal Disease: A Promising Tool

Areal-bone mineral density (aBMD) of lumbar-spine dual energy X-ray absorptiometry (DXA) scan is the most frequently used tool in evaluating BMD in pediatric patients, however its size dependency have significant impact on measurements accuracy in children with chronic kidney disease (CKD). This study aimed to evaluate the usefulness of trabecular bone score (TBS) computed during lumbar-spine DXA scan in assessing bone status in children on maintenance hemodialysis (HD). Ninety-three children on HD (aged 9-18 years) were subjected to lumbar-spine DXA-scan to obtain aBMD (g/cm2) and TBS.Z-scores of aBMD for chronological-age (aBMDZ-CA), height-age (aBMDZ-HA), and TBSZ-score were calculated using mean and SD values of 442 healthy controls. aBMD and TBS were significantly lower in short-for-age and normal height-for-age patients compared to the corresponding values of controls (p < 0.05 for all). Degraded vertebral microarchitecture (TBSZ-score < -2) was detected in 48% and 44% of male and female patients respectively. There were no significant differences in median TBSZ-score between short-for-age and normal height-for-age HD patients in male (p = 0.425) and in female (p = 0.316) patients. TBSZ-score correlated significantly with aBMDZ-CA (r = 0.234; p = 0.024) but not with aBMDZ-HA (r = 0.077; p = 0.462). Patients with history of fractures (5 patients only) had significantly lower TBS scores compared to those without fracture history (p = 0.016).

CONCLUSION

TBS is significantly reduced in children on maintenance HD and is associated with increased fracture incidence. TBS has shown to be a promising tool in assessing bone quality (trabecular microarchitecture) in children with CKD being not size-dependent as is a-BMD, for further evaluation of its potential role in therapeutic and follow-up decisions.

WHAT IS KNOWN

• In children with CKD, bone demineralization starts as early as CKD stage 2, so assessment of bone health is mandatory for follow up and therapeutic decisions. • aBMD of lumbar-spine DXA scan is the most used tool in evaluating BMD in pediatric patients, however its size dependency have significant impact on measurements made in children with CKD.

WHAT IS NEW

• TBS is significantly reduced in children on maintenance HD and associated with increased fracture incidence. • TBS has shown to be a promising tool in assessing bone quality (trabecular microarchitecture) in children with CKD being not size-dependent as is a-BMD.

Trabecular bone score (TBS) and bone mineral density (BMD) analysis by dual X-ray absorptiometry (DXA) in healthy Brazilian children and adolescents: normative data

Childhood and adolescence are crucial periods for healthy bone development throughout life. This study aims to establish normative data for trabecular bone score (TBS) and bone mineral density (BMD) measurements using dual-energy X-ray absorptiometry (DXA) in healthy Brazilian children and adolescents.

PURPOSE

To establish normative data for trabecular bone score (TBS) and bone mineral density (BMD) measurements using dual energy X-ray absorptiometry (DXA) in healthy Brazilian children and adolescents.

METHODS

Healthy children and adolescents, aged 5 to 19 years, underwent medical interview, physical examination with anthropometric measurement, pubertal stage evaluation, and bone densitometry by DXA (Hologic QDR 4500). Boys and girls were divided into 2 age groups: 5-9 years old (children) and 10-19 years old (adolescents). BMD and bone mineral content (BMC) were measured following standard procedures. TBS measurements were performed using the TBS Insight ® v3.0.3.0 software.

RESULTS

A total of 349 volunteers were enrolled in this cross-sectional study. Reference values were defined for each group of children and adolescents divided into 3-year age groups. Girls had lower values of TBS compared to boys (1.356 ± 0.116 and 1.380 ± 0.086 respectively, p = 0.029). For both boys and girls, BMC and spine BMD measurements were significantly higher in adolescent than in children (p = 0.0001; p = 0.0001; p = 0.0001, p = 0.0001, respectively). TBS range increased as pubertal development progressed. In both girls and boys, a 1-year increase in age was associated to a 0.013 increase in TBS. Body mass was a significant determinant for TBS. In girls, a 1 kg/m2 increase in BMI was associated to an average TBS increase of 0.008.

CONCLUSION

Our findings reinforce the evidence that TBS varies according to age, sex, and pubertal stage in healthy children and adolescents. This study established reference values for TBS in healthy Brazilian children and adolescents which can be used as normative data for this population.

Vitamin D and malabsorptive gastrointestinal conditions: A bidirectional relationship?

This paper is one of the outcomes of the 5th International Conference "Controversies in Vitamin D" held in Stresa, Italy from 15 to 18 September 2021 as part of a series of annual meetings which was started in 2017. The scope of these meetings is to discuss controversial issues about vitamin D. Publication of the outcomes of the meeting in international journals allows a wide sharing of the most recent data with the medical and academic community. Vitamin D and malabsorptive gastrointestinal conditions was one of the topics discussed at the meeting and focus of this paper. Participants to the meeting were invited to review available literature on selected issues related to vitamin D and gastrointestinal system and to present their topic to all participants with the aim to initiate a discussion on the main outcomes of which are reported in this document. The presentations were focused on the possible bidirectional relationship between vitamin D and gastrointestinal malabsorptive conditions such as celiac disease, inflammatory bowel diseases (IBDs) and bariatric surgery. In fact, on one hand the impact of these conditions on vitamin D status was examined and on the other hand the possible role of hypovitaminosis D on pathophysiology and clinical course of these conditions was also evaluated. All examined malabsorptive conditions severely impair vitamin D status. Since vitamin D has known positive effects on bone this in turn may contribute to negative skeletal outcomes including reduced bone mineral density, and increased risk of fracture which may be mitigated by vitamin D supplementation. Due to the immune and metabolic extra-skeletal effects there is the possibility that low levels of vitamin D may negatively impact on the underlying gastrointestinal conditions worsening its clinical course or counteracting the effect of treatment. Therefore, vitamin D status assessment and supplementation should be routinely considered in all patients affected by these conditions. This concept is strengthened by the existence of a possible bidirectional relationship through which poor vitamin D status may negatively impact on clinical course of underlying disease. Sufficient elements are available to estimate the desired threshold vitamin D level above which a favourable impact on the skeleton in these conditions may be obtained. On the other hand, ad hoc controlled clinical trials are needed to better define this threshold for obtaining a positive effect of vitamin D supplementation on occurrence and clinical course of malabsorptive gastrointestinal diseases.

Trabecular Bone Score (TBS) Varies with Correction for Tissue Thickness Versus Body Mass Index: Implications When Using Pediatric Reference Norms

Trabecular bone score (TBS) derived from secondary analysis of lumbar spine dual-energy X-ray absorptiometry (DXA) scans improves fracture prediction independent of bone mineral density (BMD) in adults. The utility of TBS to assess fracture risk in younger patients has not been established because pediatric norms have been lacking. Robust TBS reference data from the Bone Mineral Density in Childhood Study (BMDCS) have been published. TBS values for the BMDCS study were derived using an algorithm that accounts for tissue thickness (TBS_TH ) rather than the commercially available algorithm that adjusts for body mass index (BMI; TBS_BMI ). We examined the magnitude of differences in TBS_TH and TBS_BMI in a cohort of 189 healthy youth. TBS values using both algorithms increased with age and pubertal development in a similar pattern. However, TBS_BMI values were systematically and significantly higher than TBS_TH (mean = 0.06, p < 0.0001). The difference between calculated TBS_BMI and TBS_TH was not uniform. Differences were greater at lower TBS values, in males, in older individuals, in those at later Tanner stages, and in those with a greater BMI Z-score. These systematic differences preclude the development of a simple formula to allow conversion of TBS_BMI to TBS_TH "equivalents." Because of these systematic differences in these two algorithms, using an individual's TBS_BMI to calculate a Z-score using the BMDCS TBS_TH reference values results in a falsely higher TBS Z-score (differences mean = 0.73, interquartile range [IQR] = 0.3 to 1.6). Until TBS_TH software for Hologic DXA equipment becomes commercially available, BMDCS TBS reference norms should not be used. © 2023 American Society for Bone and Mineral Research (ASBMR).

Bone marrow adiposity in pediatric Crohn's disease

Patients with Crohn's disease often have low bone mineral density and an increased risk of osteoporosis. Although decreased bone formation can be seen at diagnosis, the underlying pathophysiology of suboptimal bone accrual remains poorly understood. We sought to evaluate a novel mechanism affecting osteogenesis in patients with Crohn's disease. In this case series, we evaluated bone marrow composition at the distal femur and proximal tibia of the left knee measured via magnetic resonance (MR) spectroscopy and relaxometry in five adolescents with the diagnosis of Crohn's disease. The subjects were enrolled prospectively between 2011 and 2013 at Boston Children's Hospital. Additional clinical information, including DXA scans to evaluate bone mineral density and body composition, and Crohn's disease history, such as glucocorticoid use and disease duration, were assessed. Healthy adolescents have persistent hematopoietic marrow with only 40 to 50 % fat in the long bone metaphyses. The current participants with Crohn's disease had increased marrow adiposity, with a mean fat fraction of 67.8 %. There appeared to be a trend towards higher fat fraction with shorter disease duration, while participants with the longest disease duration had the lowest fat fraction. Participants also had decreased bone density, increased fat mass, and lower lean mass, as assessed by DXA and compared to pediatric reference data. Our MRI results demonstrate increased marrow adiposity in children with Crohn's disease, especially early in the course of the disease. DXA may better demonstrate longer-term effects on bone. Additional studies are needed to evaluate bone marrow composition in these patients and to elucidate further the inverse relationship between marrow adipocytes and osteogenesis, as well as the relationship between bone marrow adiposity and body composition.

Trabecular Bone Score Reference Values for Children and Adolescents According to Age, Sex, and Ancestry

Trabecular bone score (TBS) is used for fracture prediction in adults, but its utility in children is limited by absence of appropriate reference values. We aimed to develop reference ranges for TBS by age, sex, and population ancestry for youth ages 5 to 20 years. We also investigated the association between height, body mass index (BMI), and TBS, agreement between TBS and lumbar spine areal bone mineral density (aBMD) and bone mineral apparent density (BMAD) Z-scores, tracking of TBS Z-scores over time, and precision of TBS measurements. We performed secondary analysis of spine dual-energy X-ray absorptiometry (DXA) scans from the Bone Mineral Density in Childhood Study (BMDCS), a mixed longitudinal cohort of healthy children (n = 2014) evaluated at five US centers. TBS was derived using a dedicated TBS algorithm accounting for tissue thickness rather than BMI. TBS increased only during ages corresponding to pubertal development with an earlier increase in females than males. There were no differences in TBS between African Americans and non-African Americans. We provide sex-specific TBS reference ranges and LMS values for calculation of TBS Z-scores by age and means and SD for calculation of Z-scores by pubertal stage. TBS Z-scores were positively associated with height Z-scores at some ages. TBS Z-scores explained only 27% and 17% of the variance of spine aBMD and BMAD Z-scores. Tracking of TBS Z-scores over 6 years was lower (r = 0.47) than for aBMD or BMAD Z-scores (r = 0.74 to 0.79), and precision error of TBS (2.87%) was greater than for aBMD (0.85%) and BMAD (1.22%). In sum, TBS Z-scores provide information distinct from spine aBMD and BMAD Z-scores. Our robust reference ranges for TBS in a well-characterized pediatric cohort and precision error estimates provide essential tools for clinical assessment using TBS and determination of its value in predicting bone fragility in childhood and adolescence. © 2022 American Society for Bone and Mineral Research (ASBMR).

Metabolic Bone Disorders in Children with Inflammatory Bowel Diseases

In recent years, there has been a noticeable increase in the incidence of inflammatory bowel diseases in the pediatric population. Entry observations demonstrate anemia, malabsorption, deficiencies in vitamin D and calcium. These aspects, together with the systemic action of pro-inflammatory cytokines and steroid therapy are widely recognized as factors influencing bone metabolism. Presently, however, there are very few studies that can be found in the scientific literature on metabolic disorders in patients with IBD, especially in the pediatric population as the coexistence has not been sufficiently examined and understood. This review aims to summarize the currently available literature, as well as assess which areas have information gaps and need further research.

Assessment of bone quality with trabecular bone score in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) patients have a significant risk of developing bone loss. The trabecular bone score (TBS) is a relatively new parameter used to provide information on bone quality. The study cohort included 81 patients with IBD and 81 healthy controls. Blood tests, dual-energy x-ray absorptiometry (DXA), including TBS, were assessed. Harvey–Bradshaw Index (HBI) for Crohn's disease (CD) and the Partial Mayo Score for ulcerative colitis (UC) were used for evaluation of clinical disease activity. Compared with the healthy controls, the IBD patients had lower lumbar spine (LS) bone mineral density (BMD) (1.06 ± 0.18 vs. 1.16 ± 0.15 g/cm², p < 0.005), hip BMD (0.88 ± 0.13 vs. 0.97 ± 0.13 g/cm², p < 0.005) and TBS (1.38 ± 0.1 vs. 1.43 ± 0.1, p < 0.005) values. The patients with stricturing CD had lower TBS (1.32 ± 0.13 vs. 1.40 ± 0.9, p = 0.03) and LS BMD (0.92 ± 0.19 vs. 1.07 ± 0.1, p = 0.01) values compared with those with non-stricturing CD. Multivariate regression model analysis identified HBI as independent factor associated with TBS. Our results support that all DXA parameters are lower in patients with IBD than in healthy patients. Moreover, TBS is a valuable tool for assessment of bone impairment in active CD.