Assessment of Bone Density by DXA in Poorly Controlled Children With ß-Thalassemia: Correction for Hepatic Iron Overload by Manual Analysis.

INTRODUCTION: Beta thalassemia major (BTM) is characterized by anemia and iron overload, especially with inadequate chelation therapy. Dual energy x-ray absorptiometry software (DXA) may misanalyse bone measurements due to iron deposition in organs such as the liver. Our objective was to study difference between the posterior-anterior spine measurements of bone mineral content (BMC), area (BA) and density (BMD) in poorly chelated beta thalassemia patients with and without inclusion of the liver in the DXA analysis. METHODS: We studied hemoglobin and serum ferritin concentrations in 208 patients with BTM (children n = 177, young adults n = 31). Posteroanterior spine measurements BMC, BA and areal BMD were performed using a GE iDXA. Using the tissue point typing feature (EnCore software, version 16), analysis was carried out including and excluding (manually) the iron overloaded liver. Machine generated Z-scores of L1-L4 BMD were used for analysis. RESULTS: The mean age of the study group was 12.9 ± 5.4 yr. Mean hemoglobin and serum ferritin concentrations were 8.0 ± 1.7 g/dl and 2256.9 ± 1978.0 ng/ml, respectively. The mean BMC, BA, and aBMD at the lumbar spine were 23.2 ± 11.4 g, 29.9 ± 8.5 cm2 and 0.736 ± 0.173 g/cm2 respectively with inclusion of liver that is standard machine analysis. After the liver was excluded from the analysis, the mean BMC, BA, and aBMD were 23.9 ± 11.6 g, 30.0 ± 8.6 cm2 and 0.757 ±0.173 g/cm2, respectively and the BMC and aBMD were significantly greater (p < 0.05). Mean BMD Z-score was -1.5 ± 1.2, which significantly (p < 0.05) improved to -1.3 ± 1.2 after exclusion of the liver from the analysis. CONCLUSION: In poorly chelated patients with thalassemia, inclusion of the iron-overloaded liver in the tissue analysis may exaggerate the deficit in bone parameters. Iron overloaded tissues need to be manually excluded during analysis of the PA spine.

DXA and pQCT derived parameters in Indian children with beta thalassemia major - A case controlled study.

Children with beta thalassemia major (BTM) are known to have reduced bone mass which increases incidence of non-traumatic fractures. Few studies have assessed prevalence of fractures and bone health in underprivileged children with BTM. Our objectives were to 1) determine prevalence of fractures in underprivileged Indian children with BTM, 2) assess size corrected bone density and bone geometry using Dual x-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (pQCT) in these children and healthy controls 3) determine predictors of fractures in children with BTM 4) compare differences in bone density between children with BMT with and without fractures. Bone mineral content and areal bone mineral density (aBMD) of lumbar spine and whole body and vertebral fracture assessment (VFA) was performed by DXA in 334 children (3-18 years, 167 BTM + 167 controls). Volumetric BMD (vBMD) and bone geometry were assessed by pQCT (subset, 70 BTM, 70 healthy) at distal radius. Children with BTM had higher prevalence of vertebral and long bone fractures (p < 0.05). DXA aBMD was lower in children with BTM (p < 0.05), whereas, lumbar spine bone mineral apparent density (LSBMAD) was higher (p > 0.05). Children with BTM had lower total distal radial vBMD, cortical vBMD and strength strain index (SSI) at 66% site whereas, distal radial trabecular vBMD at 4% was higher (p < 0.05). On height adjustment, children with BTM had lower muscle area and cortical thickness and higher marrow area (p < 0.05) at 66% site. Age, body size, total body less head (TBLH) aBMD and strength strain index (SSI) were important predictors of fractures in children with BTM. Thus, children with BTM had higher prevalence of non-traumatic fractures. Despite lower areal and volumetric densities, they had higher LSBMAD and trabecular densities which may be attributed to erythroid hyperplasia and iron deposition due to inadequate transfusion and chelation. As LSBMAD is raised in these children, it is unlikely to identify BTM subjects at risk of fracture; VFA thus maybe useful in identifying asymptomatic vertebral fractures.