Dual-energy X-ray Absorptiometry Variables Research Articles

Kidney Function and Body Composition in Adult Survivors of Unilateral, Non-Syndromic Wilms Tumor: A Report From the St. Jude Lifetime Cohort Study.

The relationships among treatment exposures, body composition, and estimated glomerular filtration rate (eGFR) in adult survivors of Wilms tumor have not been well studied. We evaluated body composition with dual-energy x-ray absorptiometry (DXA) and eGFR with the updated Chronic Kidney Disease Epidemiology Collaboration equations (creatinine only-eGFRCr, cystatin C only-eGFRCysC, creatinine and cystatin C-eGFRCr+CysC) without race in 134 adults previously treated for unilateral, non-syndromic Wilms tumor at St. Jude Children's Research Hospital between 1964 and 2004 with chemotherapy and with (hemiabdomen [HA] or whole abdomen [WA]) or without radiation therapy (RT). Z-scores for DXA variables were calculated using data from the National Health and Nutrition Examination Survey. WART was associated with a lower relative total (p = 0.004) and trunk (p < 0.001) lean mass, eGFRCr (p = 0.008), eGFRCysC, (p < 0.001), and eGFRCr+CysC (p < 0.001), and higher values of cystatin C (p < 0.001). Linear regression demonstrated that relative total lean mass (p = 0.009) and relative trunk lean mass (p < 0.001) Z-scores, and eGFRCr (p = 0.013) were lower among those who received WART compared to No RT patients. WART is associated with lower relative total and trunk lean mass Z-scores and eGFR, regardless of the equation used, and is lower in survivors treated with WART compared to unirradiated survivors of unilateral, non-syndromic WT. Assessments using other GFR measures may provide greater insight into the mechanism and magnitude of kidney function loss among WART-treated WT survivors.

Association of body image perception and (dis)satisfaction with adiposity in adults: The Pró-Saúde study.

Body image distortion and/or dissatisfaction may occur primarily due to body fat accumulation and/or distribution. The aim of this study was to evaluate the frequency of body image perception and (dis)satisfaction categories in adult men and women according to the adiposity classification. This is a cross-sectional study (n = 514; 33-79 years; 265 women) that is part of a prospective cohort (Pró-Saúde study). Adiposity measurements were determined by two methods: anthropometry, used to calculate the body mass index (BMI) and dual-energy X-ray absorptiometry (DXA), to estimate body fat percentage. Participants were grouped as "no excess adiposity" and "excess adiposity", considering BMI and body fat percentage (>30% for men, >40% for women). Perception and (dis)satisfaction with body image were evaluated using the Kakeshita scale, composed by 15 silhouettes, developed for the Brazilian population. Degree of distortion (perceived BMI - real BMI) and dissatisfaction (perceived BMI - desired BMI) were calculated. A high proportion of men (58.6%; 74.3%), and especially of women (82.6%; 86.8%), presented body size overestimation and dissatisfaction due to excess weight, respectively. A relevant fraction of the women (32.6%) and men (30.8%) who were dissatisfied due to excess weight did not present excess adiposity, especially if classified by DXA. Variability in degree of distortion was hardly explained by anthropometric and DXA variables in women (<5%) and men (∼22%). Both anthropometric and DXA measurements accounted for ∼30% and ∼50% of the variability in degree of dissatisfaction among women and men, respectively. Our results suggest a high frequency of body image distortion in Brazilian adult individuals, as well as dissatisfaction with excess weight, especially among women with excess adiposity. The findings indicate that anthropometric measurements explain much of the variability in degree of body image dissatisfaction in men, with no apparent advantage of the use of more refined DXA measurements.

Association between fat and fat-free body mass indices on shock attenuation during running

High amplitudes of shock during running have been thought to be associated with an increased injury risk. This study aimed to quantify the association between dual-energy X-ray absorptiometry (DEXA) quantified body composition, and shock attenuation across the time and frequency domains. Twenty-four active adults participated. A DEXA scan was performed to quantify the fat and fat-free mass of the whole-body, trunk, dominant leg, and viscera. Linear accelerations at the tibia, pelvis, and head were collected whilst participants ran on a treadmill at a fixed dimensionless speed 1.00 Fr. Shock attenuation indices in the time- and frequency-domain (lower frequencies: 3–8 Hz; higher frequencies: 9–20 Hz) were calculated. Pearson correlation analysis was performed for all combinations of DEXA and attenuation indices. Regularised regression was performed to predict shock attenuation indices using DEXA variables. A greater power attenuation between the head and pelvis within the higher frequency range was associated with a greater trunk fat-free mass (r = 0.411, p = 0.046), leg fat-free mass (r = 0.524, p = 0.009), and whole-body fat-free mass (r = 0.480, p = 0.018). For power attenuation of the high-frequency component between the pelvis and head, the strongest predictor was visceral fat mass (β = 48.79). Passive and active tissues could represent important anatomical factors aiding in shock attenuation during running. Depending on the type and location of these masses, an increase in mass may benefit injury risk reduction. Also, our findings could implicate the injury risk potential during weight loss programs.

Estimation of carcass chemical composition in beef-on-dairy cattle using dual-energy X-ray absorptiometry (DXA) scans of cold half-carcass or 11th rib cut

Abstract The aim of the present study was to estimate the chemical composition (water, lipid, protein, mineral, and energy contents) of carcasses measured postmortem using dual-energy X-ray absorptiometry (DXA) scans of cold half-carcass or 11th rib cut. One hundred and twenty beef-on-dairy (dam: Swiss Brown, sire: Angus, Limousin, or Simmental) bulls (n = 66), heifers (n = 42), and steers (n = 12) were included in the study. The reference carcass composition measured after grinding, homogenization, and chemical analyses was estimated from DXA variables using simple or multiple linear regressions with model training on 70% (n = 84) and validation on 30% (n = 36) of the observations. In the validation step, the estimates of water and protein masses from the half-carcass (R2 = 0.998 and 0.997; root mean square error of prediction [RMSEP], 1.0 and 0.5 kg, respectively) and 11th rib DXA scans (R2 = 0.997 and 0.996; RMSEP, 1.5 and 0.5 kg, respectively) were precise. Lipid mass was estimated precisely from the half-carcass DXA scan (R2 = 0.990; RMSEP = 1.0 kg) with a slightly lower precision from the 11th rib DXA scan (R2 = 0.968; RMSEP = 1.7 kg). Mineral mass was estimated from half-carcass (R² = 0.975 and RMSEP = 0.3 kg) and 11th rib DXA scans (R2 = 0.947 and RMSEP = 0.4 kg). For the energy content, the R2 values ranged from 0.989 (11th rib DXA scan) to 0.996 (half-carcass DXA scan), and the RMSEP ranged from 36 (half-carcass) to 55 MJ (11th rib). The proportions of water, lipids, and energy in the carcasses were also precisely estimated (R2 ≥ 0.882) using either the half-carcass (RMSEP ≤ 1.0%) or 11th rib-cut DXA scans (RMSEP ≤ 1.3%). Precision was lower for the protein and mineral proportions (R2 ≤ 0.794, RMSEP ≤ 0.5%). The cattle category (sex and breed of sire) effect was observed only in some estimative models for proportions from the 11th rib cut. In conclusion, DXA imaging of either a cold half-carcass or 11th rib cut is a precise method for estimating the chemical composition of carcasses from beef-on-dairy cattle.

Acute feeding has minimal effect on the validity of body composition and metabolic measures: dual-energy X-ray absorptiometry and a multi-compartment model.

Understanding the effects of acute feeding on body composition and metabolic measures is essential to the translational component and practical application of measurement and clinical use. To investigate the influence of acute feeding on the validity of dual-energy X-ray absorptiometry (DXA), a four-compartment model (4C) and indirect calorimetry metabolic outcomes, thirty-nine healthy young adults (n 19 females; age: 21·8 (sd 3·1) years, weight; 71·5 (sd 10·0) kg) participated in a randomised cross-over study. Subjects were provided one of four randomised meals on separate occasions (high carbohydrate, high protein, ad libitum or fasted baseline) prior to body composition and metabolic assessments. Regardless of macronutrient content, acute feeding increased DXA percent body fat (%fat) for the total sample and females (average constant error (CE):-0·30 %; total error (TE): 2·34 %), although not significant (P = 0·062); the error in males was minimal (CE: 0·11 %; TE: 0·86 %). DXA fat mass (CE: 0·26 kg; TE: 0·75 kg) and lean mass (LM) (CE: 0·83 kg; TE: 1·23 kg) were not altered beyond measurement error for the total sample. 4C %fat was significantly impacted from all acute feedings (avg CE: 0·46 %; TE: 3·7 %). 4C fat mass (CE: 0·71 kg; TE: 3·38 kg) and fat-free mass (CE: 0·55 kg; TE: 3·05 kg) exceeded measurement error for the total sample. RMR was increased for each feeding condition (TE: 1666·9 kJ/d; 398 kcal/d). Standard pre-testing fasting guidelines may be important when evaluating DXA and 4C %fat, whereas additional DXA variables (fat mass and LM) may not be significantly impacted by an acute meal. Measuring body composition via DXA under less stringent pre-testing guidelines may be valid and increase feasibility of testing in clinical settings.

The Irish dual-energy X-ray absorptiometry (DXA) Health Informatics Prediction (HIP) for Osteoporosis Project

PurposeThe purpose of the Irish dual-energy X-ray absorptiometry (DXA) Health Informatics Prediction (HIP) for Osteoporosis Project is to create a large retrospective cohort of adults in Ireland to examine the...

Physiological And Anthropometric Predictors Of Discrepancies Between Bioelectrical Impedance Analysis And Dual-energy X-ray Absorptiometry

Assessment methods such as dual-energy x-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) are commonly used to determine molecular-level body composition estimates in both healthy and clinical populations. Though discrepancies in body composition estimates between BIA and DXA have been previously reported, virtually no investigations have explored potential predictor variables that may explain the disagreement between these methods. PURPOSE: To explore the physiological and anthropometric predictors of discrepancies between DXA and BIA total body composition estimates. METHODS: During a single visit, 103 female participants (Mean ± SD; 33.4 ± 15.9 years; 65.6 ± 12.1 kg; 165.5 ± 6.3 cm; 32.2 ± 7.4 DXA body fat percentage [BF%]) and 76 male participants (33.8 ± 14.5 years; 83.9 ± 15.1 kg; 178.8 ± 6.6 cm; 22.9 ± 8.0 DXA BF%) underwent body composition assessment via DXA and 8-point single-frequency BIA. Potential predictors of the discrepancies between DXA and BIA body composition estimates were obtained during the same visit using air displacement plethysmography, bioimpedance spectroscopy, and 3-dimensional optical scanning. Select DXA variables were also utilized as predictors. Ordinary least squares regression was conducted to predict the differences in total fat mass (FM) and total lean soft tissue (LST) between DXA and BIA. Standardized model coefficients (β), p-values for coefficients, and R2 values were generated. RESULTS: For FM estimates, significant predictors (p ≤ 0.01) of the differences between DXA and BIA were hydration of LST (TBW:LST; β = -0.82), height (β = -0.78), percentage of TBW as extracellular fluid (%ECF; β = -0.36), and the male sex (β = 0.26). For LST, significant predictors of the errors between DXA and BIA were TBW:LST (β = 0.85), height (β = 0.77), %ECF (β = 0.40), the male sex (β = -0.22), and racial identification as Black (β = -0.09). The R2 values for regression models predicting differences between DXA and BIA were 0.80 to 0.86 for FM and 0.73 to 0.87 for LST. CONCLUSION: Hydration variables and height are primary predictors of discrepancies between DXA and BIA total body composition estimates.

Peripheral quantitative computed tomography (pQCT)-based finite element analysis provides enhanced diagnostic performance in identifying non-vertebral fracture patients compared with dual-energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry (DXA), the predominant clinical method for diagnosing osteoporosis, has limitations in identifying individuals with increased fracture risk. Peripheral quantitative computed tomography (pQCT) provides additional information and can be used to generate finite element (FE) models from which bone strength properties can be estimated. We investigated the ability of pQCT-FE properties to distinguish peripheral low-trauma fracture patients from healthy controls, by comparison with DXA and standard pQCT. One hundred and eight fracture patients (77 females aged 67.7 ± 7.9 years, 31 males aged 69.7 ± 8.9 years) were recruited from a hospital fracture liaison service. One hundred and twenty healthy community controls (85 females aged 69.8 ± 8.5 years, 35 males aged 68.9 ± 7.2 years) were recruited. Significant differences between groups were observed in pQCT-FE properties, especially at the 4% tibia site. Fracture odds increased most per standard deviation decrease in pQCT-FE at this location [shear stiffness estimate, kshear, in females, OR = 10.34, 95% CI (1.91, 43.98); bending stiffness estimate, kbend, in males, OR = 8.32, 95% CI (4.15, 33.84)]. Area under the receiver operating characteristics curve (AUROC) was observed to be highest with pQCT-FE properties at 4% the tibia site. In females, this was 0.83 for the pQCT-FE variable kshear, compared with 0.72 for DXA total hip bone density (TH aBMD) and 0.76 for pQCT tibia trabecular density (Trb vBMD); in males, this was 0.81 for the pQCT-FE variable kbend at the 4% tibia site, compared with 0.62 for TH aBMD and 0.71 for Trb vBMD. There were significant differences in AUROC between DXA and pQCT-FE variables in both females (p = 0.02) and males (p = 0.03), while no difference was observed in AUROC between primary pQCT and pQCT-FE variables. pQCT-FE modeling can provide enhanced diagnostic performance compared with DXA and, given its moderate cost, may be useful in clinical settings.

Relationships Between Dual‐Energy X‐Ray Absorptiometry Bone Mineral Content and Bone Mineral Density and Standing and Sitting Bioimpedance Spectroscopy Variables in Healthy Men and Women

Bioimpedance spectroscopy (BIS) is an advanced bioimpedance method utilizing data collected over hundreds of frequencies to generate complex Cole models. Standard gel‐backed wet electrodes used on supine patients/subjects has been the accepted method for collecting BIS data which can be used to accurately calculate fluid volumes such as intra‐cellular fluid (ICF), extracellular fluid (ECF), and total body water (TBW) as well as can be used to calculate other tissues and masses. However, the use of metal electrodes used in a standing or sitting position is not well known and offers a more rapid means of performing BIS assessments. If this new method of BIS can predict variables related to bone health, it may have the potential to help track bone loss over time in clinical populations. The purpose of the study was to compare BIS measurements taken when subjects were standing and sitting using fixed metal electrodes and evaluate the relationships of raw and fluid volume data to dual‐energy X‐ray absorptiometry (DXA) data [total bone mineral content (BMC), total bone mineral density (BMD), right forearm BMD (RA_BMD), right femur BMD (RF_BMD), anterior‐posterior spine BMD (APS_BMD)] in healthy men and women. Fifty‐five healthy men and women (m = 22, f = 33, 24 +/− 8 years, 169.5 +/− 10.5 cm, 72.3 +/− 14.9 kg) participated in the study. Whole body right side BIS measurements were taken in both a sitting and standing position with both methods utilizing metal electrodes (SOZO, ImpediMed, Inc.). Whole body DXA scans were performed using a Lunar Prodigy Primo (GE Healthcare). Raw BIS data included R0, Rinf, resistance at 50 kHz (R50), reactance at 50 kHz (Xc50), and phase angle at 50 kHz (Phase50). Calculated fluid volumes from BIS included intra‐cellular fluid (ICF), extra‐cellular fluid (ECF), and total body water (TBW). DXA variables included BMC, BMD, RA_BMD, RF_BMD, and APS_BMD. All raw variables and fluid volumes from BIS were significantly related to all DXA bone variables (p &lt; 0.047) apart from Xc50 for all DXA variables (p &gt; 0.08) other than standing and total BMC (r = −0.269, p = 0.047). Total BMC and ECF resulted in the best relationship for both sitting (r = 0.889) and standing (r = 0.914). However, ICF and TBW were also highly correlated with total BMC (r &gt; 0.860) for both sitting and standing BIS measurements. The next best relationship was between ICF and total BMD (r = 0.815). All standing BIS variables had higher relationships to DXA BMC compared to sitting BIS variables with an average improvement of r = 0.018 (0.002 to 0.056) with the exception of Phase50 (sitting r = 0.629, standing r = 0.617). In conclusion, measurements from BIS in a sitting or standing position with metal electrodes were shown to be highly related to all DXA BMC and BMD measurements with the exception of Xc50. Total body and segmental BMC and BMD may be predicted from multiple BIS variables, yet more research is needed to identify which BIS variables are ideal for each specific bone variable and measurement site. Future research is also needed to identify which BIS variables are optimal for tracking changes in bone over time in both healthy and diseased populations.Support or Funding InformationSupport provided by ImpediMed, Inc. to Eastern Kentucky University. JRM is an employee and stockholder of ImpediMed, Inc.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Relationships Between Dual‐Energy X‐Ray Absorptiometry Fat and Lean Tissue Masses and Standing and Sitting Bioimpedance Spectroscopy Variables in Healthy Men and Women

Historically, for the assessment of fluid volumes, bioimpedance spectroscopy (BIS) measurements have been performed on the right side of the body, in a supine position, using gel‐backed wet electrodes. Most bioimpedance devices utilize a standing position and metal electrodes while utilizing multiple frequencies (typically &lt; 30) and are not capable of measuring resistance at hundreds of frequencies needed for BIS calculations. BIS requires data collected over hundreds of frequencies to generate complex Cole models. From the Cole models resistances at a frequency of zero kHz (R0) and infinite kHz (Rinf) can be determined. R0 and Rinf allow for the calculation of extracellular and intracellular resistance and can be used to calculate fluid volumes without population‐based algorithms. The purpose of the study was to compare BIS measurements taken when subjects were standing and sitting using fixed metal electrodes and evaluate the relationships of raw and fluid volume data to dual‐energy X‐ray absorptiometry (DXA) data (lean soft tissue and fat tissue) in healthy men and women. Fifty‐five healthy men and women (m = 22, f = 33, 24 +/− 8 years, 169.5 +/− 10.5 cm, 72.3 +/− 14.9 kg) participated in the study. Whole body right side BIS measurements were taken in both a sitting and standing position with both methods utilizing metal electrodes (SOZO, ImpediMed, Inc.). Whole body DXA scans were performed using a Lunar Prodigy Primo (GE Healthcare). Raw BIS data included R0, Rinf, resistance at 50 kHz (R50), reactance at 50 kHz (Xc50), and phase angle at 50 kHz (Phase50). Calculated fluid volumes from BIS included intra‐cellular fluid (ICF), extra‐cellular fluid (ECF), and total body water (TBW). DXA variables included lean soft tissue (LST) and fat tissue (FT). All raw variables and fluid volumes from BIS were significantly related to DXA LST (p &lt; 0.035) with fluid volumes having the highest correlation (r &gt; 0.94) for both sitting and standing BIS measurements. All standing BIS variables had higher relationships to DXA LST compared to sitting BIS variables with an average improvement of r = 0.019 (0.009 to 0.032). Fat tissue from DXA was only significantly related to Xc50 (r = −0.315, p = 0.019) in the sitting position. In conclusion, measurements from BIS in a sitting or standing position with metal electrodes were shown to be highly related to DXA LST (highest r = 0.973). Due to the high correlation with TBW, ICF, and ECF to LST, a simple, single variable equation could be implemented using any one of the aforementioned variables to calculate LST or muscle using the current BIS method in healthy men and women. Future research should identify which of the above three variables is ideal for tracking changes in LST/muscle mass over time in both healthy and diseased populations.Support or Funding InformationSupport provided by ImpediMed, Inc. to Eastern Kentucky University. JRM is an employee and stockholder of ImpediMed, Inc.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Peripheral Quantitative Computed Tomography (pQCT) Measures Contribute to the Understanding of Bone Fragility in Older Patients With Low-trauma Fracture

Dual-energy X-ray absorptiometry (DXA) as currently used has limitations in identifying patients with osteoporosis and predicting occurrence of fracture. We aimed to express peripheral quantitative computed tomography (pQCT) variables of patients with low-trauma fracture as T-scores by using T-score scales obtained from healthy young women, and to evaluate the potential clinical utility of pQCT for the assessment of bone fragility. Fracture patients were recruited from a fracture liaison service at the Royal Melbourne Hospital. Reference pQCT data were obtained from studies on women's health conducted by our group. A study visit was arranged with fracture patients, during which DXA and pQCT were applied to measure their bone strength. A total of 59 fracture patients were recruited, and reference data were obtained from 78 healthy young females. All DXA variables and most pQCT variables were significantly different between healthy young females and fracture patients (p < 0.05), except polar stress-strain index (p = 0.34) and cortical bone density (p = 0.19). Fracture patients were divided into osteoporosis and non-osteoporosis groups according to their DXA T-scores. Significant differences were observed in most pQCT variables (p < 0.05), except trabecular area and cortical density (p > 0.9 and p = 0.5, respectively). By applying pQCT T-scores, 11 (27%) of patients who were classified as having low or medium risk of osteoporosis on DXA T-scores alone were reclassified as high risk. Results of logistic regression suggested trabecular bone density as an independent predictor of osteoporosis status. More patients can be identified with osteoporosis by applying pQCT T-score variables in older people with low-trauma fracture. Peripheral QCT T-scores contribute to the understanding of bone fragility in this population.

Discriminative ability of calcaneal quantitative ultrasound compared with dual-energy X-ray absorptiometry in men with hip or distal forearm fractures

ObjectivesThe aim of this case–control study was to compare the discriminatory ability of bone mineral density (BMD) measurements and calcaneal quantitative ultrasound (QUS) parameters for fractures and to determine fracture thresholds for each variable in men with hip or distal forearm fractures. Patients and methodsA total of 20 men with hip and 18 men with distal forearm fractures and 38 age-matched controls were included in this study. Dual-energy X-ray absorptiometry (DXA) BMD (spine and hip) and calcaneal QUS measurements were made. Area under the curves (AUCs) were calculated to assess fracture discriminatory power of DXA and QUS variables. ResultsQuantitative Ultrasound Index (QUI) T-score and Speed of Sound (SOS) were found to be the best parameters for the identification of hip and distal forearm fractures, respectively, with AUCs greater than those of DXA BMD and other QUS parameters. While a QUI T-score of ≤−1.18 could identify and rule out hip fracture cases with approximately 80% sensitivity and specificity, a SOS value of ≤1529.75 reached to almost 90% for ruling in and out distal forearm fractures. ConclusionThe discriminatory performance of calcaneal QUS variables between fractured and non-fractured men was as good as those of the DXA BMD and even better. Since men appear to sustain fractures at closer QUS variable levels than those of the DXA BMD regardless of the fracture type, it may be speculated that calcaneal QUS may be more helpful in predicting the risk of fractures when BMD alone does not demonstrate impaired bones.Level of Evidence: Level III, Study of Diagnostic Test

Assessment of regional adipose tissue depots: A DXA and CT comparison in cadavers of elderly persons

ObjectiveSince dual energy X-ray absorptiometry (DXA) cannot distinguish between different adipose tissue (AT) deposits, it remains unclear how DXA-derived body composition variables relate to anatomical tissue (sub)compartments. The aim of the present study was to compare and relate regional DXA variables with absolute tissue masses obtained by computer tomography (CT) scanning of the lower limbs in elderly persons. MethodsEleven well-preserved white Caucasian adults (seven male and four female cadavers) with a median age of 79.0years (ranging from 68 to 96years) were fully scanned with DXA and CT. Separate densities of skin tissue, AT, muscle tissue and bone were obtained by hydrostatic weighing. ResultsThe leg DXA-variables were significantly related (rho-values between 0.60 and 0.98, P<0.01) to CT-derived tissue counterparts, but showed significant systematic differences except for subcutaneous AT mass (P=0.773). After controlling for other AT depots, fat as measured by DXA (fatDXA) related only to intermuscular AT (rho=0.82, P<0.01) in males and to subcutaneous AT (rho=0.84, P<0.05) in females. ConclusionAlthough significantly interrelated, DXA and CT variables should not be used interchangeably since they have different quantitative and physiological significance. Our results suggest that fatDXA represents different parts of AT depots in elderly men and women. Since DXA is not appropriate for assessing tissue variability cautious clinical interpretation is warranted.

Use of magnetic resonance imaging to predict the body composition of pigs in vivo

The objective of the study was to evaluate whether magnetic resonance imaging (MRI) offers the opportunity to reliably analyze body composition of pigs in vivo. Therefore, the relation between areas of loin eye muscle and its back fat based on MRI images were used to predict body composition values measured by dual energy X-ray absorptiometry (DXA). During the study, a total of 77 pigs were studied by MRI and DXA, with a BW ranging between 42 and 102 kg. The pigs originated from different extensive or conventional breeds or crossbreds such as Cerdo Iberico, Duroc, German Landrace, German Large White, Hampshire and Pietrain. A Siemens Magnetom Open was used for MRI in the thorax region between 13th and 14th vertebrae in order to measure the loin eye area (MRI-LA) and the above back fat area (MRI-FA) of both body sides, whereas a whole body scan was performed by DXA with a GE Lunar DPX-IQ in order to measure the amount and percentage of fat tissue (DXA-FM; DXA-%FM) and lean tissue mass (DXA-LM; DXA-%LM). A linear single regression analysis was performed to quantify the linear relationships between MRI- and DXA-derived traits. In addition, a stepwise regression procedure was carried out to calculate (multiple) regression equations between MRI and DXA variables (including BW). Single regression analyses showed high relationships between DXA-%FM and MRI-FA (R2 = 0.89, √MSE = 2.39%), DXA-FM and MRI-FA (R2 = 0.82, √MSE = 2757 g) and DXA-LM and MRI-LA (R2 = 0.82, √MSE = 4018 g). Only DXA-%LM and MRI-LA did not show any relationship (R2 = 0). As a result of the multiple regression analysis, DXA-LM and DXA-FM were both highly related to MRI-LA, MRI-FA and BW (R2 = 0.96; √MSE = 1784 g, and R2 = 0.95, √MSE = 1496 g). Therefore, it can be concluded that the use of MRI-derived images provides exact information about important ‘carcass-traits’ in pigs and may be used to reliably predict the body composition in vivo.

Chronic low back pain is associated with reduced vertebral bone mineral measures in community-dwelling adults

BackgroundChronic low back pain (CLBP) experienced in middle-age may have important implications for vertebral bone health, although this issue has not been investigated as a primary aim previously. This study investigated the associations between CLBP and dual energy X-ray absorptiometry (DXA)-derived vertebral bone mineral measures acquired from postero-anterior and lateral-projections, among community-dwelling, middle-aged adults.MethodsTwenty-nine adults with CLBP (11 male, 18 female) and 42 adults with no history of LBP in the preceding year (17 male, 25 female) were evaluated. Self-reported demographic and clinical data were collected via questionnaires. Areal bone mineral density (aBMD) was measured in the lumbar spine by DXA. Apparent volumetric (ap.v) BMD in the lumbar spine was also calculated. Multiple linear regression models were used to examine associations between study group (CLBP and control) and vertebral DXA variables by gender, adjusting for height, mass and age.ResultsThere was no difference between groups by gender in anthropometrics or clinical characteristics. In the CLBP group, the mean (SD) duration of CLBP was 13.3 (10.4) years in males and 11.6 (9.9) years in females, with Oswestry Disability Index scores of 16.2 (8.7)% and 15.4 (9.1)%, respectively. Males with CLBP had significantly lower adjusted lateral-projection aBMD and lateral-projection ap.vBMD than controls at L3 with mean differences (standard error) of 0.09 (0.04) g/cm2 (p = 0.03) and 0.02 (0.01) g/cm3 (p = 0.04). These multivariate models accounted for 55% and 53% of the variance in lateral-projection L3 aBMD and lateral-projection L3 ap.vBMD.ConclusionsCLBP in males is associated with some lumbar vertebral BMD measures, raising important questions about the mechanism and potential clinical impact of this association.

Bioelectrical Impedance and Dual-Energy X-Ray Absorptiometry Assessments of Changes in Body Composition Following Exercise in Patients with Type 2 Diabetes Mellitus

We aimed to compare the level of agreement between leg-to-leg bioelectrical impedance analysis (LBIA) and dual-energy X-ray absorptiometry (DXA) for assessing changes in body composition following exercise intervention among individuals with Type 2 diabetes mellitus (T2DM). Forty-four adults with T2DM, age 53.2 ± 9.1 years; BMI 30.8 ± 5.9 kg/m2 participated in a 6-month exercise program with pre and post intervention assessments of body composition. Fat free mass (FFM), % body fat (%FM) and fat mass (FM) were measured by LBIA (TBF-300A) and DXA. LBIA assessments of changes in %FM and FM post intervention showed good relative agreements with DXA variables (P < 0.001). However, Bland-Altman plot(s) indicated that there were systematic errors in the assessment of the changes in body composition using LBIA compared to DXA such that, the greater the changes in participant body composition, the greater the disparity in body composition data obtained via LBIA versus DXA data (FFM, P = 0.013; %FM, P < 0.001; FM, P < 0.001). In conclusion, assessment of pre and post intervention body composition implies that LBIA is a good tool for assessment qualitative change in body composition (gain or loss) among people with T2DM but is not sufficiently sensitive to track quantitative changes in an individual's body composition.

Increased central adiposity in morbidly obese patients with obstructive sleep apnoea

With the growing epidemic of obesity, few data are available regarding adipose distribution and the severity of sleep apnoea. Our aim was to measure precisely adipose distribution with dual-energy X-ray absorptiometry (DXA) in a morbidly obese population with and without obstructive sleep apnoea (OSA). Morbidly obese female subjects without a history of OSA underwent overnight polysomnography and DXA analysis. Subject demographics, DXA variables, serum laboratory markers and physical exam characteristics were compared between individuals with and without OSA. For the study population (n= 26), mean body mass index (BMI) was 45.9 ± 7.8 kg/m(2); mean age was 47.5 ± 10.2 years and all were female. The central adiposity ratio (CAR) was higher in individuals with OSA (apnoea-hypopnoea index > 5) than those without OSA (1.1 ± 0.05 vs 1.0 ± 0.04; P = 0.004). No difference was observed in Epworth Sleepiness Scale scores, body mass index (BMI) or neck circumference between groups. OSA is associated with increased central adipose deposition in patients with a BMI of >40 kg/m(2). These data may be helpful in designing future studies regarding the pathophysiology of OSA, and potential treatment options.

Multiple imputation of missing dual‐energy X‐ray absorptiometry data in the National Health and Nutrition Examination Survey

In 1999, dual-energy x-ray absorptiometry (DXA) scans were added to the National Health and Nutrition Examination Survey (NHANES) to provide information on soft tissue composition and bone mineral content. However, in 1999-2004, DXA data were missing in whole or in part for about 21 per cent of the NHANES participants eligible for the DXA examination; and the missingness is associated with important characteristics such as body mass index and age. To handle this missing-data problem, multiple imputation of the missing DXA data was performed. Several features made the project interesting and challenging statistically, including the relationship between missingness on the DXA measures and the values of other variables; the highly multivariate nature of the variables being imputed; the need to transform the DXA variables during the imputation process; the desire to use a large number of non-DXA predictors, many of which had small amounts of missing data themselves, in the imputation models; the use of lower bounds in the imputation procedure; and relationships between the DXA variables and other variables, which helped both in creating and evaluating the imputations. This paper describes the imputation models, methods, and evaluations for this publicly available data resource and demonstrates properties of the imputations via examples of analyses of the data. The analyses suggest that imputation helps to correct biases that occur in estimates based on the data without imputation, and that it helps to increase the precision of estimates as well. Moreover, multiple imputation usually yields larger estimated standard errors than those obtained with single imputation.

In vivo discrimination of hip fracture with quantitative computed tomography: Results from the prospective European Femur Fracture Study (EFFECT)

In assessing osteoporotic fractures of the proximal femur, the main objective of this in vivo case-control study was to evaluate the performance of quantitative computed tomography (QCT) and a dedicated 3D image analysis tool [Medical Image Analysis Framework--Femur option (MIAF-Femur)] in differentiating hip fracture and non-hip fracture subjects. One-hundred and seven women were recruited in the study, 47 women (mean age 81.6 years) with low-energy hip fractures and 60 female non-hip fracture control subjects (mean age 73.4 years). Bone mineral density (BMD) and geometric variables of cortical and trabecular bone in the femoral head and neck, trochanteric, and intertrochanteric regions and proximal shaft were assessed using QCT and MIAF-Femur. Areal BMD (aBMD) was assessed using dual-energy X-ray absorptiometry (DXA) in 96 (37 hip fracture and 59 non-hip fracture subjects) of the 107 patients. Logistic regressions were computed to extract the best discriminates of hip fracture, and area under the receiver characteristic operating curve (AUC) was calculated. Three logistic models that discriminated the occurrence of hip fracture with QCT variables were obtained (AUC = 0.84). All three models combined one densitometric variable--a trabecular BMD (measured in the femoral head or in the trochanteric region)--and one geometric variable--a cortical thickness value (measured in the femoral neck or proximal shaft). The best discriminant using DXA variables was obtained with total femur aBMD (AUC = 0.80, p = .003). Results highlight a synergistic contribution of trabecular and cortical components in hip fracture risk and the utility of assessing QCT BMD of the femoral head for improved understanding and possible insights into prevention of hip fractures.

Dual energy x-ray absorptiometry analysis contributes to the prediction of hip osteoarthritis progression

IntroductionTo determine if structural bone parameters obtained from dual energy X-ray absorptiometry (DXA) contribute to the prediction of progression of hip osteoarthritis (OA) and to test if the difference between the most affected (OA) hip and the contralateral hip adds to this prediction.MethodsThe study group involves a prospective cohort of 189 patients that met the American College of Rheumatology (ARC) classification criteria for hip osteoarthritis. Progression was defined as 20% joint space narrowing or total hip replacement within a two years follow up. Software was developed to calculate geometrical aspects and bone mineral density (BMD) in different regions of interest of the proximal femur. Logistic regression was used to test if Kellgren and Lawrence (K-L) scores and DXA parameters can predict progression of OA. Models were compared using -2log likelihood tests, R2 Nagelkerke and areas under the Receiver Operator Characteristic curves, assessed using 10-fold cross validation.ResultsThe model that included the DXA variables was significantly better in predicting hip OA progression than the model with K-L score of the affected side alone (P < 0.01). The addition of the differences in DXA parameters between the most affected and contralateral hip in the superior part of the femoral head, trochanteric and intertrochanteric area further improved the prediction of progression (P < 0.05). K-L score of the affected side was still the most significant single variable in the models.ConclusionsDXA parameters can significantly contribute to the prediction of progression in patients with hip osteoarthritis. The analysis of the DXA differences between the hips of the patient represents a small but significant contribution to this prediction. These analyses show the importance of bone density changes in the etiology of OA.