Dual-energy X-ray Absorptiometry Z-score Research Articles

Disease Activity and Bone Microarchitectural Phenotype in Patients With Axial Spondyloarthritis

Background: Axial spondyloarthritis (AxSpA) is a chronic rheumatic disease characterized by spine inflammation, abnormal bone growth, and paradoxically osteoporosis and vertebral fractures. The pathogenesis of skeletal deficits in this disease is poorly understood. Purpose: We sought to evaluate volumetric bone mineral density (vBMD) and bone microarchitecture in patients with AxSpA and to identify disease-related factors associated with skeletal abnormalities. Methods: We enrolled patients between 2018 and 2021 as part of a 2-year prospective study at a single institution investigating skeletal health and the skeletal effects of interleukin-17 (IL-17) treatment. Patients with AxSpA who met Assessment in SpondyloArthritis International Society (ASAS) classification criteria by X-ray or had evidence of active inflammation on magnetic resonance imaging suggestive of sacroiliitis were referred to the study by their rheumatologists. We excluded those with a history of fragility fracture, multiple myeloma, Cushing’s disease, primary hyperparathyroidism, osteomalacia, untreated vitamin D deficiency, secondary osteoporosis, or other systemic rheumatic diseases, as well as use of oral steroids for 2 or more weeks in the 6 months prior or current use of hormone replacement therapy, current oral bisphosphonate, past or current intravenous bisphosphonate, teriparatide, or denosumab therapies. A total of 1606 patients were screened for eligibility. Of these, 30 participants were enrolled (mean age 43 years, 50% male). Patients with AxSpA had dual-energy X-ray absorptiometry (DXA) measurements of areal BMD (aBMD) and high-resolution peripheral quantitative computed tomography (HR-pQCT) measurements of vBMD microarchitecture and failure load by finite element analysis. Standardized disease assessment tools used included the Bath Ankylosing Spondylitis Disease Activity (BASDAI), Metrology Index (BASMI), and Functional Index (BASFI). Results: In the 30 included patients, mean DXA and HR-pQCT Z-scores were within 1 standard deviation (SD) of normal for all indices, except for total vBMD in males (–1.2 SD below mean). Mean symptom duration was 11.7 years and mean scores for BASDAI, BASFI, and BASMI were 4.6, 3.6, and 2.7, respectively (range 1–10, 10 = severe limitation). Longer disease duration was associated with more severe skeletal deficits at the hip and tibia—specifically, lower hip aBMD, lower meta- and inner-trabecular vBMD, lower trabecular number, and higher trabecular separation and heterogeneity. Conclusion: This study of 30 patients with AxSpA found that abnormalities in bone density and microarchitecture at weightbearing sites were associated with longer disease duration. Because of its small sample size, larger studies are needed to better characterize the pathogenic disease factors that govern skeletal damage in AxSpA.

Association Between Vertebral Bone Quality Score and Dual-Energy X-ray Absorptiometry for the Assessment of Bone Mineral Density in Adolescent Patients.

The MRI-based vertebral bone quality (VBQ) score is an assessment tool for bone mineral density (BMD) that has been validated in adults against the clinical standard of dual-energy X-ray absorptiometry (DEXA). However, VBQ has yet to be validated against DEXA for use in adolescents. This study evaluated the associations between adolescent VBQscores, DEXA Z-scores, and BMDvalues. The radiographic records of 63 consecutive patients between the ages of 11 and 21 who underwent MRI of the abdomen and pelvis and DEXA of the spine and hip were retrieved. The collected radiographic data consisted of the MRI-based VBQ score, DEXA Z-score, and BMD values of the femoral neck, L1-4 vertebrae, and total body. The VBQ score was calculated by taking the median signal intensity (MSI) from L1-L4 and the SI of the L3 cerebrospinal fluid (CSF). The VBQ score was derived as the quotient of MSIL1-L4 divided by SICSF. A mean VBQ score of 2.41 ± 0.29 was observed. Strong correlations of -0.749 (p<0.0001) and -0.780 (p<0.0001) were detected between the VBQ score and DEXA femoral neck and spine Z-scores, respectively. Correlations between VBQ score and DEXA femoral neck, spine, and total body BMD scores were -0.559 (p<0.0001), -0.611 (p<0.0001), and -0.516 (p<.0001), respectively. No significant correlations were found between the VBQ score and age, BMI, weight, or height. A mean difference in VBQ score of -0.155 (p=0.035) was observed between sexes. VBQ demonstrated moderate predictive ability for DEXA-derived Z-scores and BMD scores. VBQ scores were strongly correlated with DEXA Z-scores and moderately correlated with BMD values. The VBQ score can also be used by adolescent patients as an accessory tool to assess bone health.

Comparison of Bone Mineral Density in Children and Adolescents on CT Versus DEXA Scan.

Retrospective cross-sectional. To determine associations between Hounsfield units (HU) within a region of interest on computed tomography (CT) scans and dual energy X-ray absorptiometry (DEXA) measurements in children and adolescents. HU on CT scans as a proxy for bone mineral density (BMD) is widely used in adults. However, the utility of CT as a proxy for BMD have not been evaluated in children and adolescents. Patients younger than 18 years with a lumbar spine CT scan and a DEXA within 6 months of each other were identified. A region of interest was used to measure the HU at each lumbar vertebral body on midaxial cuts. Charts were reviewed for demographics, medical comorbidities, and DEXA reports. Correlation coefficients were calculated between the mean DEXA Z -score and the HU value. Patients were also stratified by Z -score (≥ -1.0, between -1.0 and -2.0, and ≤-2.0) and matched by age, sex and body mass index (BMI) to a cohort of healthy children and compared. A moderate correlation between mean DEXA Z -score and mean HU on CT was found ( r2 =0.42, P <0.001). After matching for age, sex and BMI, 21 patients in each group between the ages of 4 and 17 years were analyzed. The mean HU value of the control group was 231.69. When stratified by Z -score (≥ -1.0, between -1.0 and -2.0, and ≤-2.0), the mean HU values were 244.59, 216.50, and 176.54, respectively. Patients with a Z -score of ≤-2.0 had a significantly lower mean HU than matched controls. HU on lumbar CT in children and adolescents with DEXA Z -scores <-2.0, were lower when compared with healthy matched controls. This study suggests that HU on opportunistic CT scans of the spine may be used as a reasonable proxy for BMD in the pediatric population.

Bone mineral density in egyptian children with juvenile idiopathic arthritis: possible correlation to serum RANKL / osteoprotegerin (OPG) ratio and OPG gene polymorphisms

BackgroundChildren with juvenile idiopathic arthritis (JIA) are at higher risk of decreased bone mineral density (BMD) compared with healthy children due to genetic, disease and medication-related causes. This study aims to investigate the possible effects of osteoprotegerin (OPG) gene polymorphisms and serum levels of osteoprotegerin (OPG) and receptor activator of nuclear factor κB-ligand (RANKL) and RANKL/OPG ratio on BMD in children with JIA.MethodsOPG gene rs2073617, rs3134069, serum RANKL, OPG and RANKL/OPG ratio were evaluated in 60 JIA children and 100 matched healthy controls. BMD was evaluated by lumbar dual energy X-ray absorptiometry (DEXA) according to which patients were classified in 2 groups (DEXA z-score above and below − 2). Composite disease activity was measured using the Juvenile Arthritis Disease Activity Score (JADAS) 27-joints. Articular damage was scored using the juvenile arthritis damage index (JADI).ResultsPatients aged 12.05 ± 3.2 years, included 38 females and 31% had BMD z-score below-2. Systemic-onset JIA was the most frequent phenotype (38%). Genotypes and alleles frequencies of the 2 studied polymorphisms did not differ between patients and controls (p > 0.05 for all) while serum RANKL and RANKL/OPG ratio were significantly higher in patients compared to controls (p = < 0.001 and 0.03 respectively). Patients with BMD < -2 had significantly greater frequencies of rs2073617 TT genotype and T allele (p < 0.001), higher serum RANKL, RANKL/OPG ratio (p = 0.01, 0.002), female predominance (p = 0.02), higher articular and extra-articular damage index (p = 0.008,0.009) and more frequent steroid usage (p = 0.02) compared to patients with BMD z-score >-2. Multivariate analysis showed rs2073617 TT genotype, RANKL/OPG ratio, long disease duration (above 36 months) and use of steroid to be associated with decreased BMD (p = 0.03,0.04,0.01,0.01 respectively) in JIA children.ConclusionsEgyptian children with JIA have decreased BMD. rs2073617 TT genotype and T allele, RANKL/OPG ratio are possible determinants of reduced BMD in JIA. Our results underline the importance of frequent monitoring of BMD in JIA children and trying to control disease activity to preserve long term bone health.

Assessment of bone mineral density and bone turnover markers in patients with juvenile idiopathic arthritisy

Juvenile idiopathic arthritis (JIA) is one of the most common chronic inflammatory diseases occurring in childhood, associated with decreased bone mineral density (BMD) and increased risk of osteopenia and osteoporosis, which increases the fracture risk. Aim of the work: to assess BMD and bone turnover markers (serum osteocalcin for bone formation and C terminal telopeptide of type 1 collagen for bone resorption) in JIA patients and their relation to disease activity. This study included 50 patients with JIA (female:male – 20:30). The study was approved by the Ethical Research Committee and Institutional Review Board of the Faculty of Medicine, Menoufia University, Egypt (Approval number: 19519INTPH48). Written informed consent was obtained from each patient or the parents. These patients were diagnosed with JIA according to the criteria of classification of the International League of Associations for Rheumatology. BMD was measured by Dual-energy X-ray absorptiometry (DEXA) of the lumbar spine using the Z-score. The results were correlated with JIA disease duration, disease activity, bone turnover markers and serum level of vitamin D. Clinical disease activity was evaluated by juvenile arthritis disease activity score (JADAS-27). There was a significant negative correlation between DEXA Z-score and disease activity (p-value &lt; 0.001), bone turnover markers (p-value &lt; 0.001), and duration of JIA (p-value &lt; 0.05). There was a significant difference between vitamin D level and DEXA Z-score; DEXA Z-score was lower in vitamin D deficient patients. JIA patients with higher disease activity are at a higher risk of osteopenia and osteoporosis. Well-timed and efficient treatment of JIA and proper control of disease activity may help to improve the bone status and reduce the incidence of osteoporosis. Consequently, valuable targeted interventions are essential to preserve bone health during JIA.

Low energy availability surrogates associated with lower bone mineral density and bone stress injury site

Exercise is an osteogenic stimulus that should increase bone mineral density (BMD) and protect against injury. However, some female athletes have lower BMD and increased bone stress injury (BSI) risk. Impaired bone health seen in athletes may be explained by low energy availability as described by concepts of Relative Energy Deficiency in Sport (RED-S) and Female Athlete Triad (Triad). To elucidate the relationship between RED-S/Triad risk factors and BSI to high-risk (femoral neck, sacrum) and low-risk (other) bones. Cross-sectional survey and retrospective chart review. Tertiary care academic center. Female athletes aged 15-30 years participating in ≥4h/week of exercise presenting to sports medicine/orthopedics clinic who had a self-reported BSI and available dual-energy x-ray absorptiometry (DXA) measurement of BMD. Not applicable. Location of BSI. In 127 athletes, high-risk BSI was associated with surrogates of low energy availability (p=.032) and having a DXA Z-score < -1 (p=.035) but not a current/past history of menstrual dysfunction (p=.348). Accumulating RED-S/Triad risk factors increase the odds of incurring a high-risk BSI (p=.048). Adolescent/young female athletes who sustain BSI at high-risk sites (femoral neck, sacrum) may have underlying risk factors (eg, low energy availability, poor overall bone health) that should prompt further workup and referral to optimize health in these athletes.

Predictors of low bone density and fracture risk in Loeys–Dietz syndrome

PurposeLoeys–Dietz syndrome (LDS) is a connective tissue disorder affecting multiple organ systems, including bone. MethodsWe defined the bone phenotype and clinical predictors of low bone density and fracture risk in 77 patients with LDS type 1 to type 5. ResultsPatients with LDS had dual-energy x-ray absorptiometry (DXA) Z-scores significantly < 0, and 50% of children and 9% of adults had Z-scores < –2. Sixty percent of patients had ≥1 fracture, and 24% of patients with spinal x-rays scans showed spinal compression fractures. Lower body mass index, asthma, male sex and eosinophilic gastrointestinal disease were correlated with lower DXA Z-scores. The count of 5 LDS-associated skeletal features (scoliosis, pes planus, arachnodactyly, spondylolisthesis, and camptodactyly) in patients with LDS was correlated with DXA Z-score. Adults with ≥1 skeletal features had DXA Z-scores significantly < 0, and children with >2 features had DXA Z-score significantly < –2. Bone turnover markers suggest accelerated bone resorption. Data from 5 patients treated with bisphosphonates suggest a beneficial effect. ConclusionAll LDS types are associated with reduced bone density and increased risk of fracture, which may be due to increased bone resorption. Clinical features can predict a subgroup of patients at highest risk of low bone density and fracture risk.

Bone health in pediatric transfusion-dependent beta-thalassemia: Circulating osteoprotegerin and RANKL system.

While the mechanism of bone disease in thalassemia is multifactorial and still under investigation, the receptor activator of nuclear factor kappa B (RANK), receptor activator of nuclear factor kappa B ligand (RANKL), and osteoprotegerin (OPG) have pivotal roles in regulating bone metabolism. This study aimed to measure RANKL and OPG serum levels, and to detect the incidence of RANKL rs9533156, OPG rs2073618, and OPG rs2073617 genotypes in pediatric β-thalassemia patients and to assess their relation to bone mineral density. Sixty patients with transfusion-dependent β-thalassemia (TBT) patients ages 5 to 14 years were included, and 60 healthy, age- and sex-matched volunteers contributed as a control group. The patients were scanned for bone mineral density. The mean of spine dual-energy X-ray absorptiometry (DXA) Z-score in patients was -1.66 ± 1.02 standard deviation (SD). Twenty-four of them had low spine DXA Z-scores. The patients showed significantly lower OPG levels and OPG/RANKLs ratios than the control group (3.28 ± 9.11ng/ml and 11.38 ± 14.93ng/ml, and 0.01 ± 0.03 and 0.07 ± 0.09, respectively). The RANKL SNP rs9533156 TC heterozygous genotype was detected more with statistical significance in patients than controls. The incidence of OPG rs2073618 and OPG rs2073617 genotypes were 2.3 times and 1.9 times more frequent in patients than controls, respectively. The RANK/RANKL/OPG system may have an important role in regulating bone metabolism in TBT patients, although further studies are needed to clarify its role.

Relevant genetic variants are common in women with pregnancy and lactation-associated osteoporosis (PLO) and predispose to more severe clinical manifestations.

Pregnancy and lactation-associated osteoporosis (PLO) is a rare skeletal disorder characterized by early-onset osteoporosis typically manifestating with vertebral compression fractures or transient osteoporosis of the hip. We hypothesized that genetic variants may play a role in the development of PLO. This study aimed to analyze the presence of genetic variants and a potential association with the clinical presentation in PLO. 42 women with PLO were included from 2013 to 2019 in a multicenter study in Germany. All cases underwent comprehensive genetic analysis based on a custom-designed gene panel including genes relevant for skeletal disorders. The skeletal status was assessed using dual-energy X-ray absorptiometry (DXA). Subgroups were further analyzed by serum bone turnover markers (n=31) and high-resolution peripheral computed tomography (HR-pQCT; n=23). We detected relevant genetic variants in 21 women (50%), with LRP5, WNT1 and COL1A1/A2 being the most commonly involved genes. The mean number of vertebral compression fractures was 3.3±3.4 per case with a significantly higher occurrence in the subgroup with genetic variants (4.8±3.7 vs. 1.8±2.3, p=0.02). Among the total cohort, DXA Z-scores were significantly lower at the lumbar spine compared to the femoral neck (p=0.002). HR-pQCT revealed a pronounced reduction of trabecular and cortical thickness, while trabecular number was within the reference range. Eighteen women (43%) received a bone-specific therapy (primarily teriparatide). Overall, a steep increase in bone mass (+37.7%) was observed after 3years. In conclusion, pregnancy and lactation represent skeletal risk factors, which may unmask hereditary bone disorders leading to PLO. These cases were affected more severely. Nevertheless, a timely diagnosis and adequate treatment can ensure a substantial recovery potential even without specific therapy. Patients with genetically induced low bone turnover (e.g.; LRP5, WNT1) may especially benefit from osteo-anabolic medication.

Radiographic imaging, densitometry and disease severity in Autosomal dominant osteopetrosis type 2.

To characterize relationships between quantitative computed tomography bone mineral density measurements and other qualitative and quantitative imaging measures, as well as clinical metrics, in patients with autosomal dominant osteopetrosis type 2 (ADO2). Clinical and radiologic parameters of 9 adults and 3 children with autosomal dominant osteopetrosis type 2 were assessed including lumbar spine quantitative computed tomography (QCT), radiographic skeletal survey (skull base thickening; Erlenmeyer flask deformity; endobone pattern; and spine density pattern (endplate sclerosis, "anvil" appearance, or diffuse sclerosis)), dual-energy x-ray absorptiometry (DXA), tibial peripheral quantitative computed tomography (pQCT) volumetric bone mineral density (vBMD), bone turnover markers, and bone marrow failure or visual impairment. The skeletal parameter most divergent from normal was lumbar spine QCT Z-score (+ 3.6 to + 38.7). Lumbar QCT Z-score correlated positively with pQCT tibial diaphysis vBMD (Pearson correlation r = 0.73, p = 0.02) and pQCT tibial metaphysis vBMD (r = 0.87, p < 0.01). A trend towards positive lumbar QCT Z-score correlation with serum P1NP/CTX ratio (r = 0.54, p = 0.10) and lumbar DXA Z-score (r = 0.55, p = 0.10) were observed. Bone marrow failure and vision impairment occurred in those with most severe quantitative and qualitative measures, while those with less severe radiographic features had the lowest QCT Z-scores. Lumbar spine QCT provided the most extreme skeletal assessment in ADO2, which correlated positively with other radiologic and clinical markers of disease severity. Given the quantification of trabecular bone and greater variation from normal with wider range of values, lumbar QCT Z-scores may be useful to determine or detect impact of future treatments.

Oral bisphosphonate treatment in patients with Duchenne muscular dystrophy on long term glucocorticoid therapy

Osteoporosis is a major problem in patients with Duchenne muscular dystrophy (DMD), due to glucocorticoid therapy and muscle weakness. Evidence on which to base optimal prevention and treatment strategies, including bisphosphonate use, in DMD are limited. Our objective was to describe bone health outcomes of oral alendronate treatment in patients with DMD and glucocorticoid-induced osteoporosis. We retrospectively studied 54 patients treated between 2005 and 2017, and assessed changes in dual-energy x-ray absorptiometry (DXA) whole body and lumbar spine bone mineral density and content, and lateral distal femur bone mineral density. We also examined vertebral fracture development in a subset with serial spine radiographs. Pre-alendronate DXA Z-score trajectories decreased progressively. Over three years post-alendronate initiation, Z-score trajectories improved (p<0.01) at most sites compared with pre-alendronate trajectories. Height-adjusted Z-score trajectories for lumbar spine bone mineral density (p = 0.01) and whole body bone mineral content (p = 0.0004) also improved. The positive trajectories did not seem to be sustained long term in those treated up to 6 years. Radiographic vertebral findings in 43 patients appeared stable. In conclusion, oral bisphosphonate therapy using alendronate was associated with improvement of DXA bone health indices during the first three years of treatment, and may help mitigate progression of osteoporosis in glucocorticoid-treated patients with DMD.

Effect of low-dose factor VIII prophylaxis therapy on bone mineral density and 25(OH) vitamin D level in children with severe haemophilia A.

Decreased bone mineral density (BMD) is a significant morbidity in haemophilia. Vitamin D is important for the bone health of people with haemophilia. Regular factor VIII prophylaxis can prevent bleeding and arthropathy. To determine the 25(OH) vitamin D level in severe haemophilia A patients and correlate it to their Hemophilia Joint Health Score (HJHS) and dual-energy X-ray absorptiometry (DEXA). We also compared the 25(OH) vitamin D and DEXA in haemophilia A and healthy children and in haemophilia A children on prophylaxis versus on-demand therapy. Fifty severe haemophilia A patients were compared to 50 age-matched healthy boys. Patients were recruited from the Pediatric Hematology Clinic, Ain Shams University from May 2017 to April 2018. Full medical history was taken with emphasis on frequency of bleeding episodes, duration and amplitude of pain assessed by the pain score. Weight, height, body mass index and HJHS were assessed. 25(OH) vit-D3, calcium, phosphorus and alkaline phosphatase were measured. BMD was assessed using Lunar DEXA, paediatric software. People with haemophilia had significantly lower 25(OH) vit-D3 (P<.001) and DEXA z-score (P<.001) than controls. Seventy per cent of patients were on factor VIII prophylaxis twice weekly (15U/kg/dose). Significant difference was found regarding DEXA z-score (P=.012), 25(OH) vit-D3 (P=.033) and HJHS (P=.022) among patients on prophylaxis and on-demand therapy. Severe haemophilia A patients showed significantly lower 25(OH) vit-D3 and DEXA than controls. Hence, vitamin D deficiency should be tested in all people with haemophilia for early diagnosis and treatment. Low-dose prophylaxis in severe haemophilia preserves BMD and increases vitamin D. Further studies are required to evaluate the effect of different prophylaxis protocols on BMD and haemophilic arthropathy.

Serum RANKL, osteoprotegerin (OPG) and RANKL/OPG ratio in children with systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) patients have lower bone mineral density (BMD) compared with healthy individuals because of general, genetic, disease and medication-related factors. The disturbance of the receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) ratio has been reported to be associated with low BMD in many disorders in adults and children alike. The objectives of this study were (i) to assess serum OPG, RANKL and RANKL/OPG ratio levels in SLE children and controls, (ii) to determine whether the cumulative glucocorticoid (CGCS) dose had any effect on the concentration of serum RANKL, OPG and RANKL/OPG ratio, and (iii) to determine the relation of these parameters to BMD. We evaluated 50 SLE children and 50 age- and sex-matched healthy controls. RANKL and OPG were assessed in serum and compared between patients and controls. For SLE patients, a univariate followed by multivariable analysis were carried out to detect the possible predictors of the changes in RANKL, OPG and RANKL/OPG ratio levels. Lumbar BMD for all patients was assessed by dual-energy X-ray absorptiometry (DXA) scan and then correlated to different probable correlated factors. RANKL, OPG and RANKL/OPG ratio were significantly higher in SLE patients (p ≤ 0.001). Univariate analysis showed significant correlations of RANKL with CGCS (p ≤ 0.001) and with DXA scan z-score (p = 0.007): OPG was significantly correlated to Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score (p = 0.001) and anti-double-stranded DNA (p = 0.001), whereas RANKL/OPG was significantly correlated to duration of illness and DXA z-score (p = 0.002). The multivariable analysis showed that DXA z-score was an independent predictor of RANKL and RANKL/OPG ratio (p = 0.019 and 0.008, respectively), whereas SLEDAI score was an independent predictor of OPG levels. BMD was negatively correlated to disease duration (p = 0.008) and CGCS dose (p = 0.015), but no significant correlation has been found between BMD and cumulative SLEDAI score (p = 0.29). Serum RANKL/OPG ratio is elevated in Egyptian children with SLE and is considered a risk factor for reduced bone mass in these children. Other risk factors for low BMD include high CGCS dose and disease duration, supporting that osteoporosis in SLE is multifactorial.

Can digital X-ray radiogrammetry be an alternative for dual-energy X-ray absorptiometry in the diagnosis of secondary low bone quality in children?

Bone quality in children is generally measured with dual-energy X-ray absorptiometry (DXA). Digital X-ray radiogrammetry (DXR) uses BoneXpert to measure cortical bone quality on hand radiographs. This prospective study compared DXR and DXA results in children with high probability of secondary low bone quality, defined as DXA of the lumbar spine (DXALS) Z-score ≤ − 2.0. One hundred one children underwent both DXA and DXR assessment. DXALSZ-scores were also adjusted for bone age. DXR Z-scores were compared with both DXALSZ-scores, using Pearson correlations, Bland-Altman analysis, and sensitivity-specificity analysis. Mean bone age, DXR, and both DXA Z-scores were significantly impaired. Pearson correlation coefficients were significant between DXR Z-scores and both DXALSZ-scores 0.507–0.564 (p < 0.001). Bland-Altman analysis showed a mean difference of 0.05–0.48 between DXR and both DXA Z-scores and showed more than 90% similarity for both DXALSZ-scores ≤ − 2.0. DXR had a sensitivity of 67–71% and specificity of 77–83% compared to both DXALSZ-scores.Conclusion: DXR correlates well with as well DXALS as bone age-adjusted DXALSZ-scores and shows good agreement with as well DXALS as bone age-adjusted DXALSZ-scores ≤ − 2.0. DXR shows best results when compared with DXALSZ-scores.What is Known:• Digital X-ray radiogrammetry (DXR) may correlate well with dual-energy X-ray absorptiometry (DXA) in pediatric, adolescent, and adult patients.• DXR is a feasible method for assessment of bone quality in children.What is New:• This is the first prospective study in children with suspected secondary low bone quality that illustrates correlation between DXR and bone age-adjusted DXA Z-scores and that shows good agreement between DXR and DXA as bone age-adjusted DXA Z-scores ≤ −2.0.• Our results suggest DXR to be a good alternative for DXA for determining low bone quality.

BONE QUALITY IN A YOUNG COHORT OF HIV-POSITIVE PATIENTS.

In HIV+ patients, several factors related to patient and antiretroviral therapy (ART) could determine early onset of bone mineral density (BMD) disturbances. Evaluation of bone quality according to gender in patients from the HIV Romanian cohort. A cross-sectional study in "Prof. Dr. Matei Balş" National Institute for Infectious Diseases, Bucharest between 2016-2018. We collected data regarding HIV infection, ART history, viral hepatitis co-infections and we calculated patients body mass index (BMI). CD4 cell count, HIV viral load (VL), vitamin-D levels were determined. Dual-energy X-ray absorptiometry (DXA) scans were used to evaluate BMD. We enrolled 97 patients with the median age of 26 years. According to the DXA T-scores, 10 males and 8 females had osteopenia and 4 males and 4 females had osteoporosis. According to Z-scores 2 males and 1 female had osteoporosis. Hip DXA T-scores revealed osteopenia in 6 males and 9 females, whereas T and Z-scores showed osteoporosis in 2 males and 3 females. Lumbar spine (LS) T-score diagnosed osteopenia in 9 males and 6 females, while T and Z-scores revealed osteoporosis in 3 males and females. In males, low T-scores were associated with decreased BMI; low LS DXA Z-scores with low vitamin-D levels; low T and Z-scores and LS-BMD with high VL. Evaluating bone quality in patients with a long history of HIV infection, multiple factors should be taken into account.

Clinical Significance of DXA and HR-pQCT in Autosomal Dominant Osteopetrosis (ADO II)

The main hallmark of high bone mass (HBM) disorders is increased bone mineral density, potentially visible in conventional radiographs and quantifiable by other radiographic methods. While one of the most common forms of HBM is CLCN7-related autosomal dominant osteopetrosis type II (ADO II), there is no consensus on diagnostic thresholds. We therefore wanted to assess whether CLCN7-osteopetrosis patients differ from benign HBM cases in terms of (1) bone mineral density, (2) bone structure, and (3) microarchitectural abnormalities. 16 patients meeting the criteria of HBM (DXA T/Z-score≥2.5 at all sites) were included in this retrospective study. Osteologic assessment using dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HR-pQCT), and serum analyses was performed. The presence of CLCN7 and/or other HBM gene mutations affecting bone mass were tested using a custom designed bone panel. While a DXA threshold for ADO II could be implemented (DXA Z-score≥+6.0), the differences in bone microarchitecture were of lesser extent compared to the benign HBM group. All adult patients with ADO II suffered from elevated fracture rates independent from Z-score. In HR-pQCT, structural alterations, such as bone islets were found only inconsistently. In cases of HBM, a DXA Z-score≥6 may be indicative for an inheritable HBM disorder, such as ADO II. Microarchitectural bone alterations might represent local microfracture repair or accumulation of cartilage remnants due to impaired osteoclast function, but seem not to be correlated with fracture risk.

Bone Health in Children With Intestinal Failure Measured by Dual Energy X-Ray Absorptiometry and Digital X-Ray Radiogrammetry

Introduction: Children with intestinal failure (IF) receiving parenteral nutrition (PN) are at risk of developing a low bone mineral density (BMD). Next to the use of dual energy X-ray absorptiometry (DEXA), digital X-ray radiogrammetry (DXR) using BoneXpert® software has become available to obtain a Bone Health Index (BHI) in hand radiographs. Advantages are the availability of normative data for infants and the direct adjustment for bone age. Our aims were to 1) evaluate the prevalence of low BMD measured by DEXA and DXR and 2) to compare these methods in the assessment of low BMD in children with IF. Methods: A retrospective study was performed in all children with IF treated from 2000 to 2015 by the IF-team of Sophia Children’s Hospital Rotterdam, who had undergone a DEXA scan and/or a hand radiograph. Z-scores of BMD total body (BMDTB), lumbar spine (BMDLS) and BHI were collected. Low BMD and BHI were defined as Z-scores ≤ −2. DEXA and DXR results were compared for cases in which a DEXA and hand radiograph were performed within a 6 months’ interval. Results: Forty-six children were included. Twenty-one children (46%) had short bowel syndrome, 15 children (33%) had surgical IF but no SBS, and 10 children (22%) had functional IF. Overall, 24.3% of the children had a low BMD at the first DEXA at a median age of 6 years. Fifty percent had a low BHI at the first hand radiograph at a median age of 4.6 years. Median DEXA Z-scores and BHI Z-scores were significantly lower than reference scores, also for children already weaned off PN. There were no significant differences in BMD or BHI Z-scores between the different groups of IF. Age, duration of PN and surgical IF were related to lower Z-scores at the first DEXA. Paired DEXA and DXR results of 18 patients were compared, resulting in a Cohen’s kappa of 0.746 (‘substantial’) for BMD TB. Spearman’s correlation coefficients for BHI Z-scores and BMD TB were 0.856 (p<0.001). Hand radiography had a sensitivity of 90% and specificity of 86% (BMD TB, Table 1). Conclusion: Up to 50% of the children had a low BMD. Children with IF have a significantly poorer bone health than the reference population. Bone health assessment by DEXA and DXR showed good agreement, especially for Z-scores ≤ −2. Bone health measurement by DXR using the BoneXpert® software seems to be feasible for monitoring of bone health in children with IF.Figure

Risk factors and surveillance for reduced bone mineral density in pediatric cancer survivors.

Pediatric cancer survivors are at increased risk of developing low bone mineral density (BMD) due to cancer treatment. This study assessed the yield of screening for low BMD in pediatric-aged cancer survivors as per the Children's Oncology Group Long-Term Follow-Up (COG-LTFU) Guidelines, which recommend screening survivors who received steroids, methotrexate, or hematopoietic cell transplant (HCT). This is a retrospective cohort study of 475 pediatric blood cancer and noncentral nervous system solid tumor survivors screened for low BMD with dual-energy X-ray absorptiometry (DXA) as per the COG-LTFU Guidelines from 2003 to 2010. Risk factors for low BMD (DXA Z-score ≤-2) were evaluated by univariate and multivariate analysis. The mean DXA Z-score was -0.1 for both whole body and lumbar spine measurements. Among at-risk survivors, 8.2% (39/475) had low BMD. Multivariate analysis of survivors with low BMD showed significant association with male gender (odds ratio [OR] 3.4, 95% confidence interval [CI], 1.3-9.0), exposure to total body irradiation (TBI), cranial, or craniospinal radiation (OR 5.2, 95% CI, 1.8-14.9), and gonadal dysfunction (OR 4.3, 95% CI, 1.4-13.0). Methotrexate exposure was not significantly associated with low BMD. Survivors receiving HCT had a reduced risk of low BMD (OR 0.2, 95% CI, 0.1-0.9). The highest risk factors for low BMD were male gender, exposure to TBI, cranial, or craniospinal radiation, and gonadal dysfunction. Survivors receiving methotrexate or HCT therapy have the lowest risk for low BMD among those screened. Future studies should investigate risk of low BMD for survivors receiving HCT without radiation exposure.

Bone health of children with intestinal failure measured by dual energy X-ray absorptiometry and digital X-ray radiogrammetry

Children with intestinal failure (IF) receiving long-term parenteral nutrition (PN) are at risk of developing low bone mineral density (BMD). Next to the dual energy X-ray absorptiometry (DXA) method, digital X-ray radiogrammetry (DXR) using the BoneXpert software has become available to obtain the Bone Health Index (BHI) in hand radiographs. In this study we 1) evaluated the prevalence of low BMD in children with IF using DXA and DXR, 2) compared DXA and DXR results, and 3) aimed to identify factors associated with low BMD. A retrospective study was performed including all children with IF between 2000 and 2015 who underwent a DXA measurement and/or a hand radiograph. Z-scores of BMD total body (BMD TB) and lumbar spine (BMD LS), bone mineral apparent density (BMAD) and bone health index (BHI) were collected. A low BMD and low BHI were defined as a Z-score≤-2. DXA and DXR results were compared for cases in which a DXA and hand radiograph were performed within a 6 months' interval. Forty-six children were included. Overall, 24.3% of the children had a low BMD at the first DXA at a median age of 6 years; correction for growth failure (n=6) reduced this to 16.2%. Fifty percent had a low BHI at the first hand radiograph. Median DXA and BHI Z-scores were significantly lower than reference scores. Age, duration of PN and surgical IF were related to lower Z-scores at the first DXA. Paired DXA and DXR results (n=18) were compared, resulting in a Cohen's kappa of 0.746 ('substantial') for BMD TB. Spearman's correlation coefficient for BHI and BMD TB Z-scores was 0.856 (p<0.001). Hand radiography had a sensitivity of 90% and specificity of 86% (BMD TB). Up to 50% of the children had a low BMD. Children with IF have a significantly poorer bone health than the reference population, also after weaning off PN. Bone health assessment by DXA and DXR showed good agreement, especially for Z-scores≤-2. DXR assessment using BoneXpert software seems to be feasible for monitoring of bone health in children with IF.

Modeling correlates of low bone mineral density in patients with phenylalanine hydroxylase deficiency.

Phenylalanine hydroxylase (PAH) deficiency is an inherited metabolic disorder requiring life-long restriction of dietary protein and phenylalanine-free medical food. Low bone mineral density (BMD) is reported, but factors associated with BMD Z-score (standard deviations from normal) are unknown. We examined associations between clinical and dietary parameters and total BMD Z-score in PAH deficiency patients, and developed models to predict Z-score. Data collected from patients >4years of age (n = 88; mean age = 18.8 y; 61% female) included demographic, clinical, laboratory, and dietary intakes. Adjusted Spearman's correlation coefficients were calculated between parameters and TBMD Z-score, measured by dual energy x-ray absorptiometry (DXA). Parameters approaching significance (p-value < 0.10) were candidate predictors for four linear regression models predicting TBMD Z-score. To validate, model-predicted Z-scores were compared to DXA Z-scores. Mean TBMD Z-score was -0.326; 18 (20.4%) had Z-score < -1. Z-scores were positively correlated with dietary vitamin D, calcium, and medical food intake and compliance with prescription, and negatively with dietary carbohydrate, sugar, caffeine intake, glycemic load, and prescribed medical food (grams protein/day; p-value < 0.05). The best model included medical food compliance, medical food intake, caffeine intake, and bone-specific alkaline phosphatase (r-square = 0.364). This model predicted Z-score category [normal or low (<-1)] with sensitivity = 66.7%, likelihood ratio = 14.7, and AUC = 0.83 compared to DXA Z-score. No subjects had low BMD for chronological age (Z-score ≤ -2). Compliance with medical food prescription was the strongest predictor of TBMD Z-score. One model, if validated in a separate sample of patients with more cases of low BMD, showed potential to estimate TBMD Z-score using routine clinical patient parameters.