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Biomedical subjects

J Reeve

Publications and source records attributed to J Reeve.

At least 109 records · Page 6Linked to original sources
PubMed1997

Bone density variation and its effects on risk of vertebral deformity in men and women studied in thirteen European centers: the EVOS Study.

In Europe there is a 3-fold variation, according to geographical center, in risk of vertebral deformity in men and women over the age of 50. We investigated the relationship between bone density, as assessed by dual-energy X-ray absorptiometry (DEXA) of the spine and hip and prevalent vertebral deformities in 13 of the 36 centers participating in the European Vertebral Osteoporosis Study (EVOS). Each center recruited an age-stratified sample of men and women aged 50 years and over, and of those who agreed to densitometry, 288/2088 women and 233/1908 men were found to have one or more deformities of the vertebrae between T4 and L4 as assessed by the McCloskey algorithm. DEXA was in each case performed on L2-L4, the proximal femur, or both. Bone densitometry results were cross-calibrated between centers using the European Spine Phantom prototype and results expressed as bone mineral density (BMD, g/cm2). In both genders, subjects with deformities involving loss of anterior vertebral body height alone comprised over 20% of the total with deformities and these related poorly to BMD. Other classes of deformity were found by logistic regression to relate significantly to BMD in one or both genders, with odds ratios for the risk of any of these ranging from 1.67 to 2.11 for a 1 SD reduction in bone density at spine, femoral neck, or trochanter (p < 0.001). Adjusting for anthropometric variables and BMD did not remove the effect of age on risk which rose 1.67- to 1.78-fold per decade according to gender. The greater unadjusted rate of increase in deformity risk with age in women was attributable to their faster rate of bone loss with age; after adjusting for age, body mass index (BMI), and BMD at the trochanter in grams per square centimeter, men had a 2-fold higher risk of deformity than women. Analysis of the relationship between mean bone density and the prevalence of deformity in each center demonstrated no significant differences between centers in either gender, after adjusting for BMD, age, and BMI together with an a posteriori statistical adjustment for imperfect cross-calibration of densitometers. It is concluded that BMD is an important determinant of deformity risk in both genders. Together with age, BMD explains much of the differences in risk both between the sexes and between individual geographical centers in Europe.

Aged↗
PubMed1997

Cortical remodeling following suppression of endogenous estrogen with analogs of gonadotrophin releasing hormone.

The effects of estrogen suppression on osteonal remodeling in young women was investigated using transiliac biopsies (eight paired biopsies + four single pre; three single post biopsies) taken before and after treatment for endometriosis (6 months) with analogs of gonadotrophin releasing hormone (GnRH). Estrogen withdrawal increased the proportion of Haversian canals with an eroded surface (106%, p = 0.047), a double label (238%, p = 0.004), osteoid (71%, p = 0.002), and alkaline phosphatase (ALP) 116%, p = 0.043) but not those showing tartrate-resistant acid phosphatase (TRAP) activity (p = 0.25) or a single label (p = 0.30). Estrogen withdrawal increased TRAP activity in individual osteoclasts in canals with diameters greater than 50 microns (p = 0.0089) and also the number of osteons with diameters over 250 microns (p = 0.049). ALP activity in individual osteoblasts was increased but not significantly following treatment (p = 0.051). Wall thickness was significantly correlated with osteon diameter (p < 0.001). In a separate group of patients (four pairs + one post biopsy) on concurrent treatment with tibolone, there was no significant increase in the osteon density, cortical porosity, median canal diameter, or the markers of bone formation and resorption. Enzyme activities and numbers of active canals were also not increased with the concurrent treatment, but there was still an increase in the osteon diameter. As previously shown for cancellous bone, estrogen withdrawal increased cortical bone turnover. We have now shown that resorption depth within Haversian systems was also increased with treatment. The enhanced TRAP activity in individual osteoclasts supports the concept that osteoclasts are more active following estrogen withdrawal in agreement with theoretical arguments advanced previously. Understanding the cellular and biochemical mechanisms responsible for increased depth of osteoclast resorption when estrogen is withdrawn may allow the development of new strategies for preventing postmenopausal bone loss.

Acid Phosphatase↗
PubMed1996

Low bone mineral content is common but osteoporotic fractures are rare in elderly rural Gambian women.

Osteoporosis is reported to be rare in Black Africa. The low fracture incidence among North American black women is explained by a high peak bone mass and preservation of bone mineral into old age. To assess whether this is the case among Black African women, we measured bone mineral content (BMC) and bone mineral density (BMD), using single- and dual-photon absorptiometry, in 195 rural Gambian women aged over 44 years and 391 white women of comparable age from three centers in the U.K. Measurements were made at the midshaft of the radius, distal radius, lumbar spine, and femoral neck. The influence of height, weight, and nationality on BMC and BMD was analyzed. BMC and BMD decreased with age at all sites. Age, decreasing weight, but not height were independently associated with lower BMC at all sites. BMC in Gambian women was lower than in British women by 31% at the lumbar spine and 16% at the midshaft of the radius. After adjustment for age, height, and weight, BMC among Gambian women remained 24% lower at the lumbar spine and 10% lower at the radius. In women aged over 64 years, BMC at the lumbar spine was 42% lower and BMD was 31% lower in The Gambia (for all comparisons, p < 0.005). We conclude that bone mineral mass is not preserved in elderly Gambian women. However, minimal trauma fractures are rare in this population. These results challenge the concept of BMC as a primary determinant of fracture risk.

Adult↗
PubMed1996

Radial cortical and trabecular bone densities of men and women standardized with the European Forearm Phantom.

We previously showed that it is possible to cross-calibrate peripheral bone densitometers using the European Spine Phantom (ESP). We have now performed a multinational study of cross-calibrated radius bone density based on normal subjects of both sexes in eight European centers. Six centers were equipped with machines made by Scanco or Stratec for determining distal radial trabecular bone density by quantitative computed tomography (QCT) and two were equipped with Lunar SP2 single photon absorptiometry (SPA) equipment for measuring midshaft cortical bone density. Subjects recruited ranged from 20 to over 80 years of age. Over one hundred and fifteen men were studied by QCT and a different cohort of 104 men were studied with SPA; the equivalent figures for women were 235 and 123. Reference ranges were derived for bone density against age for each of the four groups, and their applicability is discussed in relation to between-center differences in the results obtained. There were insignificant differences (P > 0.05 with Bonferroni correction) between centers in the values obtained by QCT in the different populations. However, there were considerably larger and highly statistically significant differences between midshaft cortical bone density values of about 10% of overall means between subjects from eastern Finland and central Belgium (P < 0.001), with higher Finnish values. Women had considerably lower radial trabecular bone density values than men at all ages, a result that differentiates the radius from the spine. This sex difference widened after menopause. These results have important implications for understanding the contribution of bone density to the differential risk of Colles' fracture in the two sexes and suggest that further work is needed to establish young normal reference ranges for radial bone density in Europe.

Absorptiometry, Photon↗
PubMed1996

Cortical and cancellous bone in the human femoral neck: evaluation of an interactive image analysis system.

An interactive image analysis package was developed to examine whole cross-sections from the femoral neck. The package quantifies cortical width (Ct.Wi), cortical porosity (Ct.Po), and proportions of cortical, cancellous bone as a percentage of bone plus marrow area. Segmental analysis was used to quantify circumferential variations in bone distribution within the femoral cross-section. To evaluate reproducibility of data four independent operators analyzed previously prepared femoral neck sections from a 2000 BC population. Differences in total and circumferential distributions of cortical and cancellous bone with respect to gender and age of samples were demonstrated. Reproducibility was assessed using coefficients of variation (CV). Analysis of sections using a variable magnification, giving largest possible image size, rather than a set magnification reduced variation between operators for all measurements. Use of a calculated threshold significantly decreased variation between operators for the proportions of cortical and cancellous bone (p < or = 0.026). Dividing the image into 8 rather than 16 segments also improved reproducibility. There was little agreement between operators in the determination of cortical porosity. The mean CV for the other quantitative indices such as cortical width and proportions of cortical and cancellous bone ranged from 4.87% to 13.52%. The genders showed similar patterns in circumferential distribution of bone. Cortical width was significantly greater in the inferior region compared to the other areas, whereas percent cortical bone was lowest at the superior region. The center of mass (COM) for the younger age group was located anteriorly, whereas in the older samples the COM was located posteriorly of the center of area (p = 0.041). Basic data relating to cortical and cancellous bone of acceptable reproducibility in comparison with current standards in iliac histomorphometry can now be provided at modest cost in operator time and resources.

Adult↗
PubMed1996

Transcutaneous electrical nerve stimulation (TENS): a technology assessment.

The scientific evidence for clinical effectiveness of transcutaneous electrical nerve stimulation (TENS) for treatment of acute, chronic, and labor and delivery pain is assessed in this paper, and it is concluded that there is little evidence for other than a limited use of TENS. The utilization of TENS in Canadian hospitals and payments for TENS services are addressed. Some practicalities regarding the use and assessment of health technologies are discussed.

Analgesia, Obstetrical↗
PubMed1996

The development of a European questionnaire for quality of life in patients with vertebral osteoporosis.

The complaints of vertebral osteoporosis usually result from wedge or crush fractures and biconcave deformities. These are caused by a decrease of bone mass and deterioration of bone structure leading to loss of strength. Treatment of osteoporosis should result in an increase of bone mass, and the incidence of new vertebral fractures should diminish. However, new vertebral fractures are not always accompanied by pain, and disability does not well correlate with the number of vertebral fractures. Patients with osteoporosis often have other problems e.g. with taking a shower, preparing meals, gardening, walking stairs, visiting friends and attending social activities. In addition, pain and disability may influence mood and lead to depression. The assessment of quality of life should be a primary endpoint in clinical trials in patients with osteoporosis and in individual patients care. Recently, the European Foundation for Osteoporosis (EFFO) has decided a develop a questionnaire for patients with vertebral osteoporosis, i.e. patients with vertebral deformities. The questionnaire is meant for use in clinical trials. A questionnaire was made including 48 questions and 6 visual analogue scales. The questions concern the following domains: pain, activities of daily living, jobs around the house, moving, leisure and social activities, general health perception and mood. The questionnaire ("Qualeffo") has now entered the validation phase. The first study in 8 centres concerns the within-subject reproducibility, the internal coherence, and the specificity by comparing osteoporotic patients with a control group not suffering from osteoporosis or backpain.

Humans↗
PubMed1995

Determinants in Canadian health care workers of the decision to withdraw life support from the critically ill. Canadian Critical Care Trials Group.

OBJECTIVE: To examine the attitudes of health care workers regarding the withdrawal of life support. DESIGN: Cross-sectional survey. PARTICIPANTS: Attending staff, house staff, and intensive care unit (ICU) nurses in 37 Canadian university-affiliated hospitals. MAIN OUTCOME MEASURES: Health care workers' ratings of the importance of 17 factors considered in the decision to withdraw life support, and their ratings of five levels of care ranging from comfort measures to intensive care in two of 12 different clinical scenarios. RESULTS: We surveyed 1361 respondents (149 of 167 potentially eligible ICU attending staff, 142 of 173 ICU house staff, and 1070 of 1455 ICU nurses, with response rates of 89%, 82% and 74%, respectively). The most important factors were likelihood of surviving the current episode, likelihood of long-term survival, premorbid cognitive function, and age of the patient. In choosing the level of care for the patient scenarios, the same option was chosen by more than 50% of respondents in only one of 12 scenarios; opposite extremes of care were chosen by more than 10% of the respondents in eight of 12 scenarios. Respondent characteristics affecting choices included the number of years since graduation, the city and province in which they worked, the number of beds in their ICU, and their assessment of the likelihood that they would withdraw life support in comparison with their colleagues (P < .001 for all comparisons). CONCLUSIONS: While ICU health care workers consistently identify a number of patient factors as important in decisions to withdraw care, there is extreme variability, which may be explained in part by the values of individual health care providers.

Adult↗
PubMed1995

Dual X-ray absorptiometry of the proximal femur: normal European values standardized with the European Spine Phantom.

Measurements of the proximal femur by dual X-ray absorptiometry (DXA) are assuming increasing importance in clinical and epidemiological studies. However, different DXA manufacturers have adopted varying approaches to measuring the femoral neck and trochanter regions with the result that there is as yet no agreement on normal ranges and how to cross-calibrate between different machines. In this Concerted Action (of the EU's 2nd Framework Programme), 12 clinical centers in eight countries recruited a total of 855 female and 517 male Caucasian subjects who were judged to be free of conditions known to cause secondary osteoporosis and who had not been treated with drugs known to affect bone mass. The DXA machines used were made by Hologic, Lunar, and Norland. Each machine was cross-calibrated with the European Spine Phantom prototype designed by Kalender. All femoral neck and trochanter results were expressed as standardized values and were first examined for possible bias due to between-brand differences in choice of areas for measurement. On average, trochanter areas were similar between brands but Norland chose a narrower neck region for analysis. Bone mineral density (BMA or BMD g/cm2) was log-normally distributed for all groups at the femoral neck but normally distributed at the trochanter in men and postmenopausal women. There were substantial between-center differences after cross-calibration in age-adjusted mean values at both sites and also in the rates of apparent bone loss with age and the amounts of scatter within populations about mean age-adjusted values. With the proviso that locally derived normal ranges would allow more accurate comparisons for clinical purposes, European normal ranges were derived for both neck and trochanter. Data obtained with the three individual brands of machine fitted these overall ranges well. Bone loss was apparent in premenopausal women at the femoral neck but not the trochanter. Postmenopausal women's data was somewhat better fitted by reference to years since menopause than to chronological age. This work provides a basis for conducting future epidemiological and clinical studies with more than one brand of machine as long as each individual subject, if measured consecutively, is measured on the same machine throughout.

Absorptiometry, Photon↗
PubMed1995

Evolution of spinal bone loss and biochemical markers of bone remodeling after menopause in normal women.

The main objective of this study was to describe longitudinal patterns of spinal bone loss in normal women who undergo a natural menopause. The second objective was to determine if a proportion of women suffer excessively rapid postmenopausal bone loss from the spine. If this was the case it was the aim to devise a means of predicting the woman at excess risk; but if all women lost bone at similar rates, the aim was to document changing loss rates over the first 5-8 postmenopausal years. Responding women in six suburban general practices recalled for cervical smears who had their last menstrual period 9- 36 months previously were invited to participate in a longitudinal study of bone loss and the biochemical markers plasma osteocalcin and urinary hydroxyproline. Sixty-four subjects agreed to participate, a response rate of 80%. In the ensuing 5 years, six received hormone replacement therapy and are not reported on. The main outcome measures were rates of spinal bone loss over 5 years, measured by dual photon absorptiometry, and radial bone loss over the first 2 years measured to quantitative computed tomography. Spinal bone loss was similar between individuals, with 94% of the variability in the data being accounted for by a statistical model that assumed parallel rates of bone loss. A less restrictive model allowing women to have different rates of spinal bone loss accounted for 12% more of the remaining variance in the data than the previous model. However, rates of radial bone loss were more dissimilar between women than rates of spinal loss. The results of the biochemical data collected serially showed that the plasma osteocalcin rose slowly to a plateau at 5 years postmenopause; in contrast, the hydroxyproline fell progressively with time over the whole period of study. These results were interpreted as being consistent with diminishing rates of bone destruction which gradually reequilibrated with bone formation as time passed after menopause.

Absorptiometry, Photon↗
PubMed1995

Gastrointestinal calcium absorption and dietary calcium load: relationships with bone remodelling in vertebral osteoporosis.

Patients with vertebral osteoporosis have a wide range of bone loss rates, bone remodelling rates and capacities for gastrointestinal (GI) calcium absorption. To test the hypothesis that variations in GI absorptive capacity determine rates of bone loss or remodelling, we have sought relationships between calcium absorption or vitamin D metabolite levels on the one hand and rates of cancellous and cortical bone loss (measured by serial quantitative computed tomography in the radius; n = 25) or indices of bone remodelling in tetracycline-prelabelled transiliac biopsies (n = 41) on the other, in a sequential untreated group. Calcium absorption (net and true) was measured in 18-day balances and by a two-isotope deconvolution method (fractional absorption and maximum absorption rate, MAR). There was no significant seasonal effect on any of these four measures of calcium absorption (variance ratio, F = 0.52-1.61, p > 0.1) or on 1,25-dihydroxyvitamin D levels (F = 0.13, p > 0.1; range 11-69 pg/ml), notwithstanding the expected seasonal effect on 25-hydroxyvitamin D levels (mean 18.7 ng/ml, zenith mid July, semi-amplitude 7.5 ng/ml; F = 6.82, p < 0.01). Neither this metabolite nor 1,25-dihydroxyvitamin D correlated with any index of calcium absorption (p > 0.1). No measure of calcium absorption (or intake) had a significant relationship with radial cortical or cancellous bone loss (p all > 0.1) but cancellous bone loss was associated with the rate of endogenous calcium excretion (r = 0.50, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1995

European semi-anthropomorphic spine phantom for the calibration of bone densitometers: assessment of precision, stability and accuracy. The European Quantitation of Osteoporosis Study Group.

Up to now it has not been possible to reliably cross-calibrate dual-energy X-ray absorptiometry (DXA) densitometry equipment made by different manufacturers so that a measurement made on an individual subject can be expressed in the units used with a different type of machine. Manufacturers have adopted various procedures for edge detection and calibration, producing various normal ranges which are specific to each individual manufacturer's brand of machine. In this study we have used the recently described European Spine Phantom (ESP, prototype version), which contains three semi-anthropomorphic "vertebrae" of different densities made of stimulated cortical and trabecular bone, to calibrate a range of DXA densitometers and quantitative computed tomography (QCT) equipment used in the measurement of trabecular bone density of the lumbar vertebrae. Three brands of QCT equipment and three brands of DXA equipment were assessed. Repeat measurements were made to assess machine stability. With the large majority of machines which proved stable, mean values were obtained for the measured low, medium and high density vertebrae respectively. In the case of the QCT equipment these means were for the trabecular bone density, and in the case of the DXA equipment for vertebral body bone density in the posteroanterior projection. All DXA machines overestimated the projected area of the vertebral bodies by incorporating variable amounts of transverse process. In general, the QCT equipment gave measured values which were close to the specified values for trabecular density, but there were substantial differences from the specified values in the results provided by the three DXA brands. For the QCT and Norland DXA machines (posteroanterior view), the relationships between specified densities and observed densities were found to be linear, whereas for the other DXA equipment (posteroanterior view), slightly curvilinear, exponential fits were found to be necessary to fit the plots of observed versus specified densities. From these plots, individual calibration equations were derived for each machine studied. For optimal cross-calibration, it was found to be necessary to use an individual calibration equation for each machine. This study has shown that it is possible to cross-calibrate DXA as well as QCT equipment for the measurement of axial bone density. This will be of considerable benefit for large-scale epidemiological studies as well as for multi-site clinical studies depending on bone densitometry.

Absorptiometry, Photon↗