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Biomedical subjects

S Cowen

Publications and source records attributed to S Cowen.

8 recordsLinked to original sources
PubMed1997

Body composition at the bedside.

OBJECTIVE: To evaluate the use of an inexpensive hand-held bioelectric impedance analysis machine which measures lean body mass, by technical comparisons against standard instruments and techniques (an in-house bioelectric impedance machine and dual energy X-ray absorptiometry), and by performing body composition analyses in groups of potentially malnourished patients. DESIGN: Prospective simultaneous comparison of measurements made by the hand-held and in-house bioelectric analysis machines and dual energy x-ray absorptiometry. SETTING: Medical Physics Department and Gastrointestinal Unit in a university teaching hospital. SUBJECTS/METHODS: One hundred and sixty subjects were recruited into the study. Data from 58 adolescent and 14 adult volunteers and from 42 adult patients were used for technical comparisons (n = 114). Body composition information was evaluated (n = 102) for 60 adult volunteers and 42 patients (17 with eating disorders, 7 with chronic alcoholic pancreatitis and 18 with inflammatory bowel disease). OUTCOME MEASURES: Estimation of bias, limits of agreement and correlations on data from the three machines. Relationships between percentage body mass as lean, absolute weights and body mass index, in the adult subjects. RESULTS: Both resistance and calculated impedance measured by the hand-held machine significantly correlated with the impedance measured by the in-house machine (r = 0.996; P < 0.0001). An estimation of the level of agreement in percentage lean measurement between dual energy x-ray absorptiometry and hand-held bioelectrical impedance analysis machine by the Bland and Altman method showed a bias of -0.07% and satisfactory limits of agreement from -7.97% to 7.76%. Body mass index was similar in the groups of healthy men and women, but proportion of weight as lean was significantly higher in men than women. In underweight patients with eating disorders, the ratio of lean to fat varied widely; in inflammatory bowel disease patients, proportions of lean and fat were similar to controls; however patients with alcoholic pancreatitis had values for body mass index similar to controls, but had significantly lower proportion of their body weight as lean (P < 0.05). CONCLUSION: In non-obese and thin adults, an accurate two-compartment (lean, fat) measurement of body composition can be made in 10 min by using an inexpensive, hand-held, bioelectric impedance analysis machine.

Absorptiometry, Photon↗
PubMed1997

Anomalies in the measurement of changes in total-body bone mineral by dual-energy X-ray absorptiometry during weight change.

For an eating disorder study over a period of 1 year, we measured total-body bone mineral using a Hologic QDR 1000 W in a total of 157 subjects and observed anomalies that questioned the accuracy of such measurements. Using the recommended Enhanced software, a change in total bone mineral content (delta BMC) correlated positively with a change in weight (delta W; r = 0.66), but a loss of weight was associated with an increase in bone mineral areal density (BMD; r = 0.58), arising from a reduction in bone area (AREA). Both regressions were highly significant. The dominant factor in this relationship was a strong correlation between delta AREA and delta BMC, for all parts of the skeleton, r > 0.9, with a slope close to 1. This is implausible because bone area would not be expected to change. When Standard software was used, the slope of the delta BMC/delta W correlation was steeper, but the delta BMD/delta W regression became positive. An artefact of dual-energy X-ray absorptiometry processing was suspected, and phantom measurements were made. The phantom consisted of tissue-equivalent hardboard cut and stacked to form cylinders corresponding to the head, trunk, arms, and legs of a standard man. The skeleton was constructed from layers of aluminium sheet as an approximation of the average shape, BMD, BMC, and AREA in each region. When aluminium thickness was varied, BMD thresholds were found, approximately 0.4 g/cm2 for the legs and 0.2 g/cm2 for the arms. Above these, bone area rose fairly rapidly toward a plateau. At higher skeletal densities, the relationships between measured and true BMDs were close to linear, but slopes were less than unity, so that changes would be underestimated by 10-30%. Increases of thickness of the soft tissue of the phantom lowered AREA slightly. Uniform fat proportion increases led to decreases in BMC and AREA, but lard wrapped in an annulus around the limbs led to spurious increases in BMC and AREA of a similar magnitude to those observed in vivo, while BMD fell slightly, although there had been no true change of bone variables. Similar results were obtained with lard around the limbs of a volunteer. Reanalysis of phantom scans using Standard software confirmed the software differences noted in vivo. The phantom measurements offer an explanation of the anomaly in vivo and demonstrate that, under different circumstances, change in both BMC and BMD can be wrongly recorded. We believe that no valid conclusions can be drawn from measurements by the Holgic QDR 1000 W of bone changes during weight change.

Absorptiometry, Photon↗
PubMed1994

Low bone mineral density in Crohn's disease, but not in ulcerative colitis, at diagnosis.

BACKGROUND/AIMS: The pathogenesis of low bone mineral density in patients with inflammatory bowel disease is unclear, and the relevance of secondary osteopenic influences is controversial. Our aim was to study bone mineral density in newly diagnosed patients. METHODS: Bone mineral density and biochemical parameters of bone metabolism were measured in 15 patients with Crohn's disease and 15 patients with ulcerative colitis, all of whom were newly diagnosed. Lumbar and forearm bone mineral densities were measured by dual energy x-ray absorptiometry, and Z scores were obtained by comparison with age- and sex-matched normal values. Twenty-three patients had repeat measurements 1 year later, and 20 had received systemic steroids. RESULTS: At diagnosis, the mean Z score for patients with Crohn's disease (spine, -1.06 +/- 0.86; forearm, -1.04 +/- 0.86) was significantly lower than that for patients with ulcerative colitis (spine, -0.03 +/- 1.16; forearm, 0.11 +/- 1.24). Inflammatory activity, disease localization, body mass index, smoking habits, sex, physical activity, or biochemical parameters did not account for this difference. Spine and forearm Z scores were significantly correlated. Mean Z scores after 1 year were not significantly different from initial Z scores. CONCLUSIONS: At diagnosis, low bone mineralization is a feature of Crohn's disease but not ulcerative colitis. Treatment with corticosteroids did not result in further bone loss in 1 year.

Adolescent↗
PubMed1993

Osteoporosis and normal weight bulimia nervosa--which patients are at risk?

This study assesses the degree of bone mineral loss in women with active DSM IIIR bulimia nervosa. The subjects in this study were 20 GP-referred female patients of normal weight who met criteria for bulimia nervosa and 16 healthy age, sex and weight matched controls. Dual energy X-ray densitometry of lumbar L1-L4 vertebrae was performed on all subjects. The patients with bulimia nervosa had a significantly lower mean lumbar bone mineral density (0.964 g/cm2) than the control group (1.043 g/cm2, p < 0.01). Within the patient group only subjects with a past history of anorexia nervosa had a significantly lower mean bone mineral density (BMD) than the controls. Small sample sizes limit the power of the study, however significant correlations were found between duration of amenorrhoea, low BMI and lumbar BMD. Bulimic patients do suffer from osteoporosis. Risk factors for this may be; a past history of anorexia nervosa, prolonged secondary amenorrhoea, and a persistently low body mass index.

Adolescent↗
PubMed1990

Calibration of a prompt neutron activation analysis facility for the measurement of total body protein.

Prompt neutron activation analysis with 252Cf has been used to measure total body protein. Since simultaneous irradiation and detection generated a high count rate at the detectors the nucleonic system was optimised to reduce distortions in the gamma ray energy spectrum. Tissue-equivalent phantoms were used to calibrate the apparatus. A total of 53 studies was performed on 39 normal subjects. Ratios of total body protein to fat-free mass agreed well with those from other centres and with cadaver studies. Duplicate measurements of 14 subjects gave a coefficient of variation of +/- 2.9% for a measurement of total body protein, which is close to that calculated from the known errors of the technique of +/- 2.7%. The whole body dose equivalent was 0.17 mSv.

Activation Analysis↗
PubMed1990

Evaluation of bioelectrical impedance analysis for body composition measurements in anorexia nervosa.

Many established methods of measuring body composition are time consuming and require complex equipment which is not generally available. Bioelectrical impedance analysis is a technique which utilises the difference in conductivity between fat and lean tissues at radiofrequencies. It uses inexpensive equipment which is simple to use and does not involve the use of ionising radiation. We have evaluated this technique in 44 studies on 38 anorexic females with a wide range of body mass index. Fat free mass was obtained from the mean of three established methods. The initial calibration was derived from 21 studies on 19 anorexics. Fat free mass was regressed against impedance and body habitus parameters to establish the prediction equation with the smallest standard error (1.12 kg). Values of fat free mass derived using this prediction equation were then compared with the other methods in a prospective study. The error of the bioelectrical impedance technique compares favourably with the established methods, even in anorexic patients with very low body mass index.

Adult↗
PubMed1989

Nationwide survey of postsecondary education services for students with learning disabilities.

Postsecondary services for students with learning disabilities vary a great deal from campus to campus, and published guides to postsecondary education services are often inaccurate and incomplete. A nationwide survey was conducted to investigate student service provisions in 2-year colleges and 4-year colleges and universities. The purpose of the study was to identify and catalog postsecondary education service goals and options for students with learning disabilities, and to determine differences between the goals service providers have for these students and services actually provided. The findings and their implications for service providers at both high school and college levels are discussed.

Data Collection↗