A comparison of two mathematical models of the impact of mass drug administration on the transmission and control of schistosomiasis.

The predictions of two mathematical models describing the transmission dynamics of schistosome infection and the impact of mass drug administration are compared. The models differ in their description of the dynamics of the parasites within the host population and in their representation of the stages of the parasite lifecycle outside of the host. Key parameters are estimated from data collected in northern Mozambique from 2011 to 2015. This type of data set is valuable for model validation as treatment prior to the study was minimal. Predictions from both models are compared with each other and with epidemiological observations. Both models have difficulty matching both the intensity and prevalence of disease in the datasets and are only partially successful at predicting the impact of treatment. The models also differ from each other in their predictions, both quantitatively and qualitatively, of the long-term impact of 10 years' school-based mass drug administration. We trace the dynamical differences back to basic assumptions about worm aggregation, force of infection and the dynamics of the parasite in the snail population in the two models and suggest data which could discriminate between them. We also discuss limitations with the datasets used and ways in which data collection could be improved.

Soil-Transmitted Helminths: Mathematical Models of Transmission, the Impact of Mass Drug Administration and Transmission Elimination Criteria.

Infections caused by soil-transmitted helminthias (STHs) affect over a billion people worldwide, causing anaemia and having a large social and economic impact through poor educational outcomes. They are identified in the World Health Organization (WHO) 2020 goals for neglected tropical diseases as a target for renewed effort to ameliorate their global public health burden through mass drug administration (MDA) and water and hygiene improvement. In this chapter, we review the underlying biology and epidemiology of the three causative intestinal nematode species that are mostly considered under the STH umbrella term. We review efforts to model the transmission cycle of these helminths in populations and the effects of preventative chemotherapy on their control and elimination. Recent modelling shows that the different epidemiological characteristics of the parasitic nematode species that make up the STH group can lead to quite distinct responses to any given form of MDA. When connected with models of treatment cost-effectiveness, these models are potentially a powerful tool for informing public policy. A number of shortcomings are identified; lack of critical types of data and poor understanding of diagnostic sensitivities hamper efforts to test and hence improve models.

Studies of the Transmission Dynamics, Mathematical Model Development and the Control of Schistosome Parasites by Mass Drug Administration in Human Communities.

Schistosomiasis is global in extent within developing countries, but more than 90% of the at-risk population lives in sub-Saharan Africa. In total, 261 million people are estimated to require preventive treatment. However, with increasing drug availability through donation, the World Health Organization has set a goal of increasing coverage to 75% of at-risk children in endemic countries and elimination in some regions. In this chapter, we discuss key biological and epidemiological processes involved in the schistosome transmission cycle and review the history of modelling schistosomiasis and the impact of mass drug administration, including both deterministic and stochastic approaches. In particular, we look at the potential impact of the WHO 2020 schistosomiasis treatment goals.

What is required in terms of mass drug administration to interrupt the transmission of schistosome parasites in regions of endemic infection?

BACKGROUND: Schistosomiasis is endemic in 54 countries, but has one of the lowest coverages by mass drug administration of all helminth diseases. However, with increasing drug availability through donation, the World Health Organisation has set a goal of increasing coverage to 75 % of at-risk children in endemic countries and elimination in some regions. In this paper, we assess the impact on schistosomiasis of the WHO goals in terms of control and elimination. METHODS: We use an age-structured deterministic model of schistosome transmission in a human community and the effect of mass drug administration. The model is fitted to baseline data from a longitudinal re-infection study in Kenya and validated against the subsequent re-infection data. We examine the impact on host worm burden of the current treatment trend, extrapolated to meet the WHO goals, and its sensitivity to uncertainty in important parameters. We assess the feasibility of achieving elimination. RESULTS: Model results show that the current treatment trend, extrapolated to the WHO goals, is able to greatly reduce host worm burdens. If coverage is continued at the same level beyond 2020, elimination is possible for low to moderate transmission settings, where transmission intensity is defined by the basic reproduction number, R0. Low levels of adult coverage have a significant impact on worm burden in all settings. Model validation against the re-infection survey demonstrates that the age-structured model is able to match post-treatment data well in terms of egg output, but that some details of re-infection among school children and young adults are not currently well represented. CONCLUSIONS: Our work suggests that the current WHO treatment goals should be successful in bringing about a major reduction in schistosome infection in treated communities. If continued over a 15 year period, they are likely to result in elimination, at least in areas with lower transmission.

What impact will the achievement of the current World Health Organisation targets for anthelmintic treatment coverage in children have on the intensity of soil transmitted helminth infections?

BACKGROUND: It is the aim of the World Health Organisation to eliminate soil-transmitted helminths (STH) as a health problem in children. To this end, the goal is to increase anthelmintic treatment coverage for soil transmitted helminths to reach 75 % in pre-school aged and school aged children by 2020 in endemic countries. In this paper, we use mathematical models to investigate the impact of achieving this goal on the burdens of Ascaris lumbricoides, Trichuris trichuria and hookworm. METHODS: We employ a deterministic fully age-structured model of STH transmission and mass drug administration to examine the changes in worm burden in response to the known and projected coverage trends in children up to 2020 and beyond. Parameters are estimated from worm expulsion data and age intensity profiles before treatment using maximum likelihood methods. Model validation is performed using reinfection studies for Ascaris and analyses are conducted to assess the sensitivity of the predicted outcomes to variation in parameter estimates including transmission intensity (R0), children's contributions to the pool of infective stages and drug coverage levels. RESULTS: The impact of the required increase in coverage trends are quite different across the three species. Ascaris burdens are reduced dramatically by 2020 with elimination predicted within studied the setting a further 10 years. For Trichuris and hookworm, however, impact is more limited, due to issues of drug efficacy (Trichuris) and distribution of worms in the population (hookworm). Sensitivity analysis indicates that results are largely robust. However, validation against Ascaris data indicates that assumptions concerning re-infection among children may have to be revised. CONCLUSIONS: The 2020 coverage target is predicted to have a major impact on Ascaris levels by 2020. However, there is evidence from model validation that Ascaris in children is more resilient to treatment than currently assumed in the model. Broader coverage across all age classes is required to break transmission for hookworm and alternative dual drug treatment approaches are needed for Trichuris.

In vivo precision of the GE Lunar iDXA densitometer for the measurement of total body composition and fat distribution in adults.

In vivo precision for body composition measurements using dual energy X-ray absorptiometry (DXA; GE Lunar iDXA, GE Healthcare, Bucks, UK) was evaluated in 52 men and women, aged 34.8 (s.d. 8.4; range 20.1-50.5) years, body mass index (25.8 kg/m(2); range 16.7-42.7 kg/m(2)). Two consecutive total body scans (with re-positioning) were conducted. Precision was excellent for all measurements, particularly for total body bone mineral content and lean tissue mass (root mean square 0.015 and 0.244 kg; coefficients of variation (CV) 0.6 and 0.5%, respectively). Precision error was CV 0.82% for total fat mass and 0.86% for percentage fat. Precision was better for gynoid (root mean square 0.397 kg; CV 0.96%) than for android fat distribution (root mean square 0.780 kg, CV 2.32%). There was good agreement between consecutive measurements for all measurements (slope (s.e.) 0.993-1.002; all R(2) = 0.99). The Lunar iDXA provided excellent precision for total body composition measurements. Research into the effect of body size on the precision of DXA body fat distribution measurements is required.

Transmission dynamics and mechanisms of endemicity of scrapie in the UK sheep population.

SUMMARYScrapie is a fatal neurological disease of sheep which is endemic in the United Kingdom. It is one of the family of transmissible spongiform encephalopathies (TSEs) that includes BSE. In this paper, we developed a micro-simulation model for scrapie in the UK sheep population, incorporating the genetic and structural diversity of the population and infectious contact between flocks through trading. The simulation was fitted to epidemiological data from a range of sources. We found a detection/reporting probability of 16% (95% CI 12-17) for animals dying of scrapie. Prevalence of infected animals in the population was about 0.15%. Infected individuals were found in 9% of flocks overall, rising to 60% in Shetland and 75% in Swaledale flocks. Mean values of R0 for flocks varied with breed from 2.43 (Shetland) to 0.21 (Suffolk). We also examined the possible long-term persistence of scrapie in the UK flock in the absence of any intervention.

Control of scrapie in the UK sheep population.

Scrapie is a fatal transmissible spongiform encephalopathy (TSE) of sheep, endemic in the UK for centuries. Interest in the disease has been heightened over the last decade by the possibility of the related BSE being transmissible to and between sheep and a range of control interventions has been proposed and implemented. In this paper, we examined the effect of these policies and their components on observed case rate, susceptible allele frequency and R0 within the framework of a large simulation model of the British sheep population and its breeding and trading structure. We compared interventions with the natural fade-out of scrapie in the population through loss of susceptible genotypes in the absence of control. We compare the results of interventions with the natural course of the scrapie epidemic. Our model suggested that scrapie will persist in the national flock for 300-400 years with the impact on gene frequencies confined largely to high case-rate breeds, such as Shetland and Swaledale. We found the National Scrapie Plan (NSP) to be the most effective in terms of the removal of both susceptible genotypes and scrapie from the population. Complete eradication of scrapie can be achieved within 32 years (95% CI 23-43 years). The Compulsory Scrapie Flock Scheme (CSFS) is as effective as the NSP in reducing the observed case rate but has a limited impact on the frequencies of susceptible genotypes in the population overall. In combination with the NSP, eradication of scrapie is achieved >10 years faster. Of the components of the CSFS, the breeding and culling aspects are each almost as effective as the full policy, with trading restrictions contributing little. We have speculated on the impact of control measures on the possibility BSE infection within the national flock by examining their effect on flock R0 for BSE across different breeds.

Validity of foot-to-foot bio-electrical impedance analysis body composition estimates in overweight and obese children.

OBJECTIVES: To examine the validity of body composition estimates obtained using foot-to-foot bio-electrical impedance analysis (BIA) in overweight and obese children by comparison to a reference four-compartment model (4-CM). SUBJECTS/METHODS: 38 males: age (mean +/- sd) 13.6 +/- 1.3 years, body mass index 30.3 +/- 6.0 kg.m(-2) and 14 females: age 14.7 +/- 2.2 years, body mass index 32.4 +/- 5.7 kg.m(-2) participated in the study. Estimates of fat-free mass (FFM), fat mass (FM) and percentage body fat (PBF) obtained using a Tanita model TBF-310 and a 4-CM (derived from body mass, body volume, total body water and total body bone mineral measurements) were compared using bias and 95% limits of agreement (Tanita minus 4-CM estimates). RESULTS: Body composition estimates obtained with the Tanita TBF-310 were not significantly different from 4-CM assessments: for all subjects combined the bias was -0.7kg for FM, 0.7kg for FFM and -1.3% for PBF. However, the 95% limits of agreement were substantial for individual children: males, up to +/-9.3kg for FFM and FM and +/-11.0% for PBF; females, up to +/-5.5kg for FFM and FM and +/-6.5% for PBF. CONCLUSIONS: The Tanita TBF-310 foot-to-foot BIA body composition analyser with the manufacturer's prediction equations is not recommended for application to individual children who are overweight and obese although it may be of use for obtaining group mean values.

Exercise during childhood and adolescence: a prophylaxis against cystic fibrosis-related low bone mineral density? Exercise for bone health in children with cystic fibrosis.

Inadequate bone mineral accrual during growth and accelerated bone demineralisation in adulthood are recognised as additional and serious complications for patients with cystic fibrosis (CF). However, little attention has been given to preventative strategies for this population. Inadequate bone accrual during childhood and adolescence, and premature bone loss, lead to a failure to attain an optimal peak bone mass, osteoporosis and fracture in patients with CF. Pharmaceutical treatments may assist in the improvement of bone in patients with CF, but these are usually not preferable for use in children. Evidence indicates that regular, weight-bearing exercise significantly enhances bone accrual in healthy children. This paper reviews the literature concerning the potential for weight-bearing exercise to improve bone mineral accrual in children with CF. All relevant literature since 1979 was obtained and reviewed from the Medline, PubMed, Cochrane and PEDro data base. Evidence concerning the efficacy of exercise for bone health in CF is lacking. There have been no controlled trials investigating the value of weight-bearing exercise for bone accrual in children with CF. As exercise may offer an effective and enjoyable strategy to improve the bone development in children who have CF, exercise should be a high priority for randomised controlled trials in this population.

Can ultrasound propagate in the joint space of a human knee?

A large body of evidence supports the principle that the use of low-intensity pulsed ultrasound with a frequency of 1.5 MHz can reduce fracture healing time. It is hypothesized that similar therapeutic benefits may be achieved in damaged articular cartilage. This study looks specifically at a 22-mm circular ultrasound transducer delivering ultrasound with a frequency of 1.5 MHz. A human cadaver knee was imaged using CT, the resulting images were used to help map a number of hydrophone positions in the joint from which measurements were taken. The experimental results suggest that at best there is a 30-mm window in which to place the ultrasound transducer for ultrasound to propagate through the joint space. In terms of a clinical device delivering an I(SATA) of 30 mW cm(-2) to anterior regions of the joint, the I(SATA) in posterior regions will at best be in the region of 10 mW cm(-2). The clinical implications of this are not known and require further investigation.

Low lumbar spine bone mineral density in both male and female endurance runners.

There have been many reports of low bone mineral density (BMD) in female endurance runners. Although there have been several reports of low BMD in male runners, it is unclear how comparable the problem is to that in females. We compared BMD between male and female endurance runners and with a reference population. One hundred and nine endurance runners (65 females, 44 males) aged 19-50 years participated and had been training regularly for at least 3 years (32-187.2 km week(-1)) in events from 3 km to the marathon. BMD was measured at the lumbar spine (L2-L4) and hip by DXA. A questionnaire assessed training and menstrual status. Lumbar spine T scores were similar in male and female runners (-0.8 (0.8) versus -0.8 (0.7); f = 0.015; P = 0.904) as were total hip T scores (0.6 (7.9) versus 0.5 (9.2); f = 0.192; P = 0.662). The proportion of male runners with low lumbar spine BMD (<-1.0) (n = 16 from 44) compared to that of females (n = 27 from 65) (P = 0.675). Males had lower spine T scores than eumenorrhoeic females (-0.8 (0.7) versus -0.4 (0.7); f = 5.169; P = 0.03). There were moderate negative correlations between weekly running distance and lumbar spine BMD in males and females (r(2) = 0.267; 0.189; P < 0.001), independent of menstrual status in females (r(2) = 0.192; P < 0.001). Lumbar spine but not hip T scores were greater in runners who participated in resistance training at least twice-a-week (male: -0.4 versus -1.1; female: -0.5 versus -1.1; P < 0.01). Using multiple regression, running distance (-) and BMI (+) together best predicted lumbar spine T scores (r(2) = 0.402; P < 0.01) in females. Although weak, BMI (+) best predicted hip T scores (r(2) = 0.167; P < 0.05). In males, running distance and training years (-) together best predicted lumbar spine T scores (r(2) = 0.400; P < 0.01). Training years (-) best predicted hip T scores (r(2) = 0.361; P < 0.01). To conclude, our findings suggest that male runners face the same bone threat at the spine, as female runners. Further research in male athletes is required. Incorporation of regular resistance training into an athlete's training programme may be a useful preventative strategy.

Pediatric in vivo cross-calibration between the GE Lunar Prodigy and DPX-L bone densitometers.

Dual energy x-ray absorptiometry (DXA) machine cross-calibration is an important consideration when upgrading from old to new technology. In a recent cross-calibration study using adult subjects, close agreement between GE Lunar DPX-L and GE Lunar Prodigy scanners was reported. The aim of this work was to cross-calibrate the two machines for bone and body composition parameters for pediatrics from age 5 years onwards. One-hundred ten healthy volunteers aged 5-20 years had total body and lumbar spine densitometry performed on DPX-L and Prodigy densitometers. Cross-calibration was achieved using linear regression and Bland-Altman analysis. There was close agreement between the machines, with r2 ranging from 0.85 to 0.99 for bone and body composition parameters. Paired t-tests demonstrated significant differences between machines that were dependent on scan acquisition mode, with the greatest differences reported for the smallest children. At the lumbar spine, Prodigy bone mineral density (BMD) values were on average 1.6% higher compared with DPX-L. For the total body, there were no significant differences in BMD; however, there were significant differences in bone mineral content (BMC) and bone area. For small children, the Prodigy measured lower BMC (9.4%) and bone area (5.8%), whereas for larger children the Prodigy measured both higher BMC (3.1%) and bone area (3.0%). A similar contrasting pattern was also observed for the body composition parameters. Prodigy values for lean body mass were higher (3.0%) for small children and lower (0.5%) for larger children, while fat body mass was lower (16.4%) for small children and higher (2.0%) for large children. Cross-calibration coefficients ranged from 0.84 to 1.12 and were significantly different from 1 (p<0.0001) for BMC and bone area. Bland-Altman plots showed that within the same scan acquisition modes, the magnitude of the difference increased with body weight. The results from this study suggest that the differences between machines are mainly due to differences in bone detection algorithms and that they vary with body weight and scan mode. In general, for population studies the differences are not clinically significant. However, for individual children being measured longitudinally, cross-over scanning may be required.

Effect of oral bisphosphonates on bone mineral density and body composition in adult patients with cystic fibrosis: a pilot study.

BACKGROUND: Approximately two thirds of adult patients with cystic fibrosis have reduced bone mineral density and up to one quarter have osteoporosis at one or more sites. Any bone mineral deficits are likely to be exacerbated in patients following lung transplantation by their immunosuppressive regimen. Vertebral collapse and rib fractures will impair the ability to cough and the efficacy of physiotherapy treatments. METHODS: Patients attending the Leeds Regional Adult Cystic Fibrosis Unit with either osteopenia or osteoporosis on dual energy x ray absorptiometry (DXA) scanning were offered treatment with oral bisphosphonates after exclusion of abnormal vitamin D, calcium, or phosphate levels, abnormal thyroid function, or hypogonadism. Those declining treatment or patients with a normal initial DXA scan formed the control group. A second DXA scan was performed after a mean of 2.4 years in the treatment group and 2.9 years in the non-treatment group. Patients in the active group were asked to complete a short questionnaire detailing their adherence to treatment. RESULTS: The medians of the differences in annual changes in bone parameters between treatment and control groups showed significant differences in bone mineralisation in favour of the treatment group at the lumbar spine (L2-L4), the femoral neck, and for total body measurements. There were no significant differences in weight, height, or body composition in either patient group. Most treated patients stated that they adhered to treatment most of the time. CONCLUSION: Treatment with oral bisphosphonates may improve bone mineralisation in adult patients with cystic fibrosis. The results of this pilot study need to be further explored in a randomised controlled trial.

Rising obesity and expanding waistlines in schoolchildren: a cohort study.

A cohort of schoolchildren was followed up over 6 years from 1996 to 2001. In the final year, 315 of 500 targeted children were measured. Body mass index (BMI) increased substantially over time (p<0.001), indicating a further rise in obesity into the secondary school years. Two new indicators of obesity were also measured. Waist circumference scores rose as substantially as BMI (p<0.001), and may be of particular significance given the association between abdominal girth in adults and cardiovascular morbidity. International Obesity Task Force measures were found to be more stringent than previous criteria, with no significant change noted over the time period.

Bone density, body composition and menstrual history of sedentary female former gymnasts, aged 20-32 years.

Few studies have examined the effects of retirement from sports involving regular, high impact and weight bearing activity on bone mass. This cross-sectional study compared total body and regional areal bone mineral density (aBMD, g/cm(2)) within female former gymnasts and women who had never participated in structured sport or exercise, and explored relations between aBMD of these former gymnasts and their duration of retirement. Eighteen sedentary female former gymnasts (GYM) and 18 sedentary controls (CON) were recruited. GYM displayed a broad range of duration of retirement (3-12 years) and a wide age range (20-32 years). GYM and CON were paired individually to match for age, body mass and stature. GYM had commenced training at least 3 years pre-menarche and had trained post-menarche for 2 or more years. They had trained continuously for 5-12 years and had retired between age 14 and 22 years. Measurements of aBMD and body composition were made using dual energy X-ray absorptiometry (DXA). Group mean values of physical and skeletal characteristics were compared using paired t-tests. Linear regression was used to explore possible relations of aBMD within GYM to duration of retirement. GYM displayed a higher aBMD than CON at all measurement sites, which ranged in magnitude from 6% for the total body ( P=0.004), to 11% for the total femur ( P=0.006). Elevations of aBMD within GYM equated to T-scores ranging from +0.8 (arms) to +1.7 (legs). There were no differences in body composition or age of menarche between groups, although 11 of 18 GYM reported a history of irregular menses. There was no significant decline of aBMD with increasing duration of retirement in GYM. The results suggested that an elevated bone mass in female former gymnasts was retained during early adulthood, in spite of a cessation of training for up to 12 years.

Comparison of body composition methods in overweight and obese children.

The objective of the present study was to investigate the accuracy of percent body fat (%fat) estimates from dual-energy X-ray absorptiometry, air-displacement plethysmography (ADP), and total body water (TBW) against a criterion four-compartment (4C) model in overweight and obese children. A volunteer sample of 30 children (18 male and 12 female), age of (mean +/- SD) 14.10 +/- 1.83 yr, body mass index of 31.6 +/- 5.5 kg/m, and %fat (4C model) of 41.2 +/- 8.2%, was assessed. Body density measurements were converted to %fat estimates by using the general equation of Siri (ADPSiri) (Siri WE. Techniques for Measuring Body Composition. 1961) and the age- and gender-specific constants of Lohman (ADPLoh) (Lohman TG. Exercise and Sport Sciences Reviews. 1986). TBW measurements were converted to %fat estimates by assuming that water accounts for 73% of fat-free mass (TBW73) and by utilizing the age- and gender-specific water contents of Lohman (TBWLoh). All estimates of %fat were highly correlated with those of the 4C model (r > or = 0.95, P < 0.001; SE < or = 2.14). For %fat, the total error and mean difference +/- 95% limits of agreement compared with the 4C model were 2.50, 1.8 +/- 3.5 (ADPSiri); 1.82, -0.04 +/- 3.6 (ADPLoh); 2.86, -2.0 +/- 4.1 (TBW73); 1.90, -0.3 +/- 3.8 (TBWLoh); and 2.74, 1.9 +/- 4.0 DXA (dual-energy X-ray absorptiometry), respectively. In conclusion, in overweight and obese children, ADPLoh and TBWLoh were the most accurate methods of measuring %fat compared with a 4C model. However, all methods under consideration produced similar limits of agreement.

Estimates of percentage body fat in young adolescents: a comparison of dual-energy X-ray absorptiometry and air displacement plethysmography.

OBJECTIVE: To evaluate the accuracy of percentage body fat (%fat) estimates from air displacement plethysmography (ADP) against an increasingly recognised criterion method, dual-energy X-ray absorptiometry (DXA), in young adolescents. DESIGN: Cross-sectional evaluation. SETTING: Leeds General Infirmary, Centre for Bone and Body Composition Research, Leeds, UK. SUBJECTS: In all, 28 adolescents (12 males and 16 females), age (mean+/-s.d.) 14.9+/-0.5 y, body mass index 21.2+/-2.9 kg/m(2) and body fat (DXA) 24.2+/-10.2% were assessed. RESULTS: ADP estimates of %fat were highly correlated with those of DXA in both male and female subjects (r=0.84-0.95, all P<0.001; s.e.e.=3.42-3.89%). Mean %fat estimated by ADP using the Siri (1961) equation (ADP(Siri)) produced a nonsignificant overestimation in males (0.67%), and a nonsignificant underestimation in females (1.26%). Mean %fat estimated by ADP using the Lohman (1986) equations (ADP(Loh)) produced a nonsignificant underestimation in males (0.90%) and a significant underestimation in females (3.29%; P<0.01). Agreement between ADP and DXA methods was examined using the total error (TE) and methods of Bland and Altman (1986). Males produced a smaller TE (ADP(Siri) 3.28%; ADP(Loh) 3.49%) than females (ADP(Siri) 3.81%; ADP(Loh) 4.98%). The 95% limits of agreement were relatively similar for all %fat estimates, ranging from +/-6.57 to +/-7.58%. Residual plot analyses, of the individual differences between ADP and DXA, revealed a significant bias associated with increased %fat (DXA), only in girls (P<0.01). CONCLUSIONS: We conclude that ADP, at present, has unacceptably high limits of agreement compared to a criterion DXA measure. The ease of use, suitability for various populations and cost of ADP warrant further investigation of this method to establish biological variables that may influence the validity of body fat estimates.

Cross-calibration of GE/Lunar pencil and fan-beam dual energy densitometers--bone mineral density and body composition studies.

OBJECTIVE: In vitro and in vivo comparisons of bone mineral density (BMD) and body composition between GE/Lunar pencil (DPXL) and fan-beam (PRODIGY) absorptiometers. DESIGN: Comparison of BMD, bone mineral content (BMC) and area of lumbar spine (L2-L4), femoral neck and total body. Total body composition compartments tissue (TBTissue), fat (TBF), lean tissue (TBLean) and %TBF were also compared. SETTING: Centre for Bone and Body Composition Research, University of Leeds. PHANTOMS/SUBJECTS: A range of spine phantoms, a variable composition phantom (VCP) and total body phantom. A total of 72 subjects were included for the in vivo study. RESULTS: In vitro: A small significant underestimation of BMD by the Prodigy compared to the DPXL ranging from 0.7 to 2% (p<0.05-0.001) for the spine phantoms. The Prodigy underestimated the VCP %Fat. Although the Prodigy underestimated phantom TBBMD by 1.1+/-1.0%, TBBMC and area were reduced by 8.2+/-1.4 and 7.3+/-1.0%, respectively. The Prodigy overestimated TBTissue 1508 g (2.2%), TBLean 588 g (1.2%), TBF 919 g (4.8%) and %TBF (0.8%). In vivo: BMD cross-calibration was only required in the femoral neck, DPXL(BMD)=0.08+0.906*PRODIGY(BMD). The Prodigy had higher estimates for TBTissue 1360 g (2.3%), TBLean 840 g (2.0%), TBF 519 g (3.4%), TBBMC 32.8 g (1.3%) and %TBF (0.3%). Cross-calibration equations were required for TBTissue(DPXL)=-1158+0.997*TBTissue(PRODIGY) and TBBMC(DPXL)= 89.7+0.949*TBBMC(PRODIGY). CONCLUSIONS: Small differences between the two absorptiometers for both BMD and body composition can be made compatible by use of cross-calibration equations and factors. The discrepancy in body composition compartments requires further research.