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Biomedical subjects

B Oldroyd

Publications and source records attributed to B Oldroyd.

At least 37 records · Page 2Linked to original sources
PubMed1997

The effect of arteriovenous fistulae in haemodialysis patients on whole body and segmental bioelectrical impedance.

BACKGROUND: Bioelectrical impedance (BIA) is a potentially useful method for measuring body water and soft-tissue composition in patients with chronic renal failure. The majority of whole body impedance is derived from the limbs with only a small contribution from the trunk, and thus abnormalities of the limbs could have an exaggerated effect on estimates of total body impedance. METHODS: This study investigated the effect of arteriovenous fistulae in the arm in haemodialysis patients on body composition measurement by whole body BIA. Body composition estimates from measurements on fistula and non-fistula sides of the body were compared and segmental impedance measurements of the arms were also performed. RESULTS: Whole body resistance was markedly lower on the fistula side of the body compared with the nonfistula side at 517.1 (124.3) omega compared with 561.5 (121.2) omega, P < 0.0005. This difference was accounted for by differences in the arm segments. This was attributed to swelling of the fistula arm which had a greater mid-arm circumference at 28.5 (2.1) cm compared with the contralateral side at 27.5 (2.0) cm, P < 0.05. This resulted in greater estimates for total body water from the fistula side at 38.6 (10.0) kg compared with 36.6 (8.6) kg from the non-fistula side, P < 0.05 and fat-free mass at 51.1 (11.8) kg from the fistula side compared with 49.1 (11.2) kg from the non-fistula side, P < 0.005. Estimates of body fat from the fistula side, 13.1 (6.9) kg, were less than the nonfistula side, 15.0 (6.0), P < 0.005. CONCLUSIONS: The presence of arteriovenous fistulae for vascular access in haemodialysis patients may have a significant effect on estimates of body composition by BIA.

Arm↗
PubMed1997

Assessment of renal osteodystrophy in dialysis patients: use of bone alkaline phosphatase, bone mineral density and parathyroid ultrasound in comparison with bone histology.

Bone biopsies were studied in 73 patients to determine if a two-site radioimmunometric assay for serum bone alkaline phosphatase (BAP), total serum alkaline phosphatase (ALP), serum intact parathyroid hormone (iPTH), hand X-rays, regional bone mineral density (BMD) measurements and parathyroid enlargement detected by ultrasonography could accurately predict renal osteodystrophy. In the patients studied 57 had hyperparathyroid bone disease, 4 mixed renal osteodystrophy, 3 adynamic bone disease, 1 osteomalacia and 8 normal histology. Serum BAP, ALP and iPTH correlated positively with mineral apposition rate, osteoblastic, osteoid and eroded surface. In the diagnosis of hyperparathyroid bone disease serum iPTH was the most sensitive investigation, detecting 81% of patients at a level > 100 pg/ml but with a specificity of only 66%. Serum BAP was more sensitive, 70% at a level of > 10 ng/ml, than serum total ALP, 30% at a level of 300 IU/l, with similar specificities, 92 and 100%, respectively. Ultrasound detection of an enlarged parathyroid gland had a sensitivity of 64% and a specificity of 100% for the diagnosis of hyperparathyroid bone disease. Hand X-rays had a poor sensitivity, 47%, but a high specificity, 92%, for the detection of hyperparathyroid bone disease. The majority of patients had regional BMD values within the normal reference range and this test was of poor discriminatory value. The non-invasive markers were unable to distinguish between patients with low turnover, mild hyperparathyroidism and patients with normal histology. In conclusion the measurement of serum iPTH is a useful screening tool for the detection of hyperparathyroid bone disease which can be confirmed by the finding of a raised serum BAP or parathyroid enlargement. For definitive diagnosis, however, the gold standard remains bone biopsy and at present one cannot recommend any non-invasive method as an adequate substitute.

Adult↗
PubMed1997

Measurement of total body water and urea kinetic modelling in peritoneal dialysis.

Studies of the effect of Kt/V (urea) on prediction of outcome in patients on peritoneal dialysis have shown conflicting results. We performed this study to examine the effects of the measurement of V by varying techniques on the calculation of Kt/V, using body water estimated by deuterium oxide dilution (D2O dilution) as the criterion method for estimation of V. Studies were performed in 20 peritoneal dialysis patients. Kt was calculated from 24-hour dialysate and urine collections and V estimated by D2O dilution, Watson formulae, 58% of body weight, bioelectrical impedance (BIA) and 73% of fat-free mass estimated by DEXA. V was also measured in 35 healthy controls. Hydration, expressed as body water by D2O dilution as a percentage of fat-free mass estimated by DEXA did not differ between peritoneal dialysis patients 71.0 (4.9)% and a healthy control group 71.1 (5.0)%. Mean Kt/V using D2O dilution was 2.14 (0.36). The other techniques resulted in a significantly lower Kt/V; Watson equations 2.01 (0.35), p < 0.005, BIA 1.93 (0.31), p < 0.0001, DEXA 2.06 (0.28), p < 0.05, 58% body weight 1.83 (0.38), p < 0.0001. Limits of agreement of Kt/V by the simpler techniques compared with D2O dilution [mean difference of (other techniques -D2O dilution) as % of mean values +/- 95% limits of agreement] were Watson equation -5.9 +/- 15.3%, BIA -10.1 +/- 15.5%, DEXA -3.4 +/- 13.5% and 58% body weight -9.9 +/- 23.5%. Differences in Kt/V from estimates using D2O dilution were significantly negatively correlated with body fat for 58% body weight (r = -0.80, p < 0.0001) and the Watson formulae (r = -0.49, p < 0.05) but not for BIA or DEXA. We conclude that clinically significant variation in Kt/V may occur due to the estimation of V and may account for the uncertainty of the value of Kt/V as a predictor of outcome in peritoneal dialysis patients. Estimating V by BIA and DEXA did not have any benefit over the Watson formulae in terms of agreement with D2O dilution, though did avoid systematic errors related to body fat. Estimation of V as a fixed proportion of body weight is clearly inferior to the other techniques.

Absorptiometry, Photon↗
PubMed1996

Segmental bioelectrical impedance in patients with chronic renal failure.

We studied changes in hydration by whole body and segmental (arm, leg and trunk)bioelectrical impedance analysis (BIN in patients with chronic renal failure (CRF) undergoing haemodialysis and continuous ambulatory peritoneal dialysis (CAPD). Mean (SD) fluid removal by haemodialysis of 1.38 (0.81) kg was overestimated by whole body BIA at 1.83 (1.13) I, P < 0.005. Peritoneal fluid drained from the CAPD patients of 1.88 (0.36) kg was underestimated by whole body BIA at 0.59 (0.35) I, P < 0.0001. Resistance and reactance significantly increased for the whole body and all segments (except trunk reactance) after haemodialysis. Drainage of CAPD fluid resulted in smaller increases in trunk resistance and whole body resistance. The increase in trunk resistance was less in CAPD than haemodialysis patients, even though the volume of fluid drained from the peritoneum in CAPD patients exceeded that removed from the whole body during haemodialysis. We conclude that whole body BIA does not estimate changes in body fluid with sufficient accuracy to be of use in clinical practice. Segmental impedance may be a potentially useful method for investigation of regional changes in body fluid, though is insensitive to changes within the peritoneal cavity.

Journal Article↗
PubMed1996

Four-component model of body composition in chronic renal failure comprising dual-energy X-ray absorptiometry and measurement of total body water by deuterium oxide dilution.

1. Assessment of nutrition in patients with chronic renal failure by body composition measurement techniques may be affected by variable hydration. 2. This study aimed to derive a four-component model of body composition (consisting of fat, protein, total body water and body mineral) from a combination of dual-energy X-ray absorptiometry and total body water measured by deuterium oxide dilution, allowing assessment of body protein stores without the effect of variation in hydration. Patients with chronic renal failure on haemodialysis, peritoneal dialysis and conservative treatment and a control group were studied. Patients with chronic renal failure were at an 'ideal' state of hydration on clinical assessment. 3. Hydration was defined by total body water as a percentage of fat-free mass measured by dual-energy X-ray absorptiometry, and no differences were found between chronic renal failure subgroups and control subjects (except in the female undialysed chronic renal failure subgroup). Hydration was significantly correlated with percentage total body fat in the control groups but not in patients with chronic renal failure. 4. Lean tissue measured by dual-energy X-ray absorptiometry was significantly reduced in three of the six chronic renal failure groups compared with control subjects (male and female patients on haemodialysis and female patients on peritoneal dialysis). Protein estimated from the four-component model failed to detect these abnormalities. 5. Lean tissue measured by dual-energy X-ray absorptiometry in normal subjects strongly correlated with fat-free mass measured by total body potassium in normal subjects (male r = 0.91; female r = 0.89, both P < 0.0001). The correlation of protein estimated from the four-component model with fat-free mass measured by total body potassium was far weaker in male control subjects (r = 0.51, P < 0.05) and not significant in female control subjects (r = 0.38, P not significant). In the normal subjects protein estimated from the four-component model showed a much greater variation from protein estimated by total body potassium than did protein estimated simply as 27% of dual-energy X-ray absorptiometry fat-free mass minus total body mineral. 6. Hydration in patients with chronic renal failure in whom fluid balance is believed to be normal on clinical criteria does not differ from that in normal subjects. The combined model of dual-energy X-ray absorptiometry and total body water is not a useful method for the measurement of body protein.

Absorptiometry, Photon↗
PubMed1996

Influence of changes in peritoneal fluid on body-composition measurements by dual-energy X-ray absorptiometry in patients receiving continuous ambulatory peritoneal dialysis.

The effect of the presence of intraabdominal fluid on measurement of body composition by dual-energy X-ray absorptiometry (DXA) was determined by scanning 14 patients who were receiving continuous ambulatory peritoneal dialysis (CAPD) before and after the drainage of peritoneal dialysate, resulting in a mean (+/- SD) weight loss of 1.81 +/- 0.34 kg. DXA showed changes in whole-body soft tissue, which were correctly localized to the trunk region on regional analysis. Changes in DXA estimates of mean total lean tissue, 1.78 +/- 0.94 kg, and trunk lean tissue, 1.87 +/- 0.84 kg, were very similar to the actual change in body weight. However, the DXA estimate of change in total soft tissue, 2.11 +/- 0.44 kg, was significantly greater than the change in body weight by 0.3 kg (P < 0.005); the difference was accounted for by a tendency for a reduction in the estimate of body fat affecting the trunk region after drainage of dialysate. DXA was also less good at detecting changes in individual subjects. Estimates of total and regional bone mineral content and bone mineral density were not affected by the drainage of the dialysis fluid.

Absorptiometry, Photon↗
PubMed1996

Measurement of body composition in chronic renal failure: comparison of skinfold anthropometry and bioelectrical impedance with dual energy X-ray absorptiometry.

OBJECTIVE: To compare the validity of skinfold anthropometry (SFA) and bioelectrical impedance (BIA) for the measurement of body composition in patients with chronic renal failure (CRF). DESIGN: We compared measurement of % total body fat (%TBF) and fat-free mass (FFM) by BIA and SFA, with dual energy X-ray absorptiometry (DEXA) as the criterion method to determine their value in groups of patients with CRF and a group of normal controls. SETTING: Renal Unit, Leeds General Infirmary and Centre for Bone and Body Composition Research, University of Leeds, UK. RESULTS: 95% levels of agreement of BIA and SFA with DEXA (using the method of Bland & Altman) showed considerable variation, which was greater for both techniques in CRF patients than in a normal control group. In normal subjects, BIA derived values for % TBF and FFM showed a closer agreement with DEXA than did SFA (% TBF BIA-DEXA -8.2 to +3.8%; %TBF SFA-DEXA -4.6 to +12.1%; FFM BIA-DEXA -2.5 to +5.8kg; FFM SFA-DEXA -7.9 to +3.8 kg). However, in CRF patients no differences in the 95% levels of agreement were observed for % TBF or FFM derived from BIA or SFA compared with DEXA (%TBF BIA-DEXA -13.7 to +8.3%; %TBF SFA-DEXA -13.0 to +9.4%; FFM BIA-DEXA -5.1 to +9.6 kg; FFM SFA-DEXA -5.6 to +9.1 kg). CONCLUSIONS: In CRF, errors of both BIA and SFA in comparison with DEXA are greater than in normal subjects. The magnitude of the limits of intermethod difference are relatively much greater for measurement of % TBF than FFM for both BIA and SFA in CRF patients and control subjects.

Absorptiometry, Photon↗
PubMed1996

Whole body and regional body composition in patients with chronic renal failure.

BACKGROUND: Nutritional state is a powerful prognostic factor in chronic renal failure (CRF). Techniques for the assessment of nutrition have limitations which are often most marked in the presence of renal disease. We have used techniques of body composition analysis to assess the nutritional state of groups of patients with CRF. METHODS: Body composition was measured in groups of patients with advanced CRF on conservative treatment, peritoneal dialysis, and haemodialysis and the results compared with a healthy control group. The selection criteria for the CRF patients ensured that they were "stable' with no recent intercurrent illness, and dialysis adequacy was satisfactory according to currently accepted targets. RESULTS: Whole body dual energy X-ray absorptiometry (DEXA) found significant reduction in lean tissue in haemodialysis patients and female peritoneal dialysis patients. Regional analysis with DEXA showed reduction in limb (especially arm), lean tissue in CRF patients, with arm lean tissue being reduced in all three CRF groups for females and both dialysis groups for males. Limb/trunk lean tissue ratios were significantly reduced for all CRF groups. Bioelectrical impedance showed reductions of fat-free mass in the same groups who had reduced whole body lean tissue with DEXA, but skinfold anthropometry failed to detect any significant reduction in fat-free mass. CONCLUSIONS: We conclude that even in "healthy' groups of CRF patients receiving adequate dialytic and dietary management, lean tissue depletion is a common problem. Regional analysis by DEXA, with measurement of limb lean tissue mass is a more sensitive method for the detection of lean tissue depletion than measurement of whole body lean tissue in patients with CRF.

Absorptiometry, Photon↗
PubMed1996

Measurement of total body water by bioelectrical impedance in chronic renal failure.

OBJECTIVE: Abnormalities of body hydration are common in patients with advanced chronic renal failure (CRF) and may be associated with important adverse clinical effects, even in the absence of clinical features of fluid retention or depletion. Bioelectrical impedance analysis (BIA) is a simple, non-invasive method of measuring body water content and thus could be of use in the management and study of patients with CRF. This study was performed to assess the ability of BIA to measure total body water (TBW) in patients with CRF. DESIGN: TBW was measured by two different impedance systems, with comparison of the results with TBW determined by deuterium oxide dilution (D2O). SETTING: Renal Unit, Leeds General Infirmary and Centre for Bone and Body Composition Research, University of Leeds, UK. RESULTS: The range of the 95% limits of method agreement between BIA and D2O expressed as a percentage of the mean for the group was +/- 13.4% for the RJL 101A system and +/- 15.6% for the Holtain system in controls. For the whole CRF group the limits were moderately greater than controls at +/- 17.3% (RJL) and +/- 21.9% (Holtain). Analysis of subgroups of the CRF patients showed the smallest limits in those receiving peritoneal dialysis (+/- 15.5% RJL and 18.2% Holtain). Limits were greater for patients on haemodialysis (+/- 16.0% RJL and +/- 23.8% Holtain) and undialysed patients (+/- 20.1% and +/- 23.0%). CONCLUSIONS: BIA is less accurate for the measurement of TBW in patients with CRF than in healthy subjects, though in some groups of patients the effect of CRF on the validity of this technique may be only mild. Abnormalities of reactance suggest that abnormal variability in the distribution of fluid between intra- and extracellular compartments is the major cause of reduced accuracy of TBW calculated by BIA in CRF patients.

Aged↗
PubMed1994

Comparison of changes in bone mineral in idiopathic and secondary osteoporosis following therapy with cyclical disodium etidronate and high dose calcium supplementation.

OBJECTIVE: Our clinical practice has been to offer treatment with cyclical disodium etidronate and high dose calcium supplements (1500-1600 mg/day) to all female patients with osteoporosis who are unable or unwilling to take hormone replacement therapy (HRT), and male osteoporotics. In a retrospective study we compared the effect of this treatment on measures of bone mineral over a 12-month period in women with post-menopausal and secondary osteoporosis. We also assessed its effects in 10 male osteoporotics. DESIGN: A retrospective analysis of 83 consecutive patients with osteoporosis who completed 12 months of treatment with disodium etidronate and calcium and who had a dual energy X-ray absorptiometry (DEXA) scan at baseline and following 12 months of therapy. PATIENTS: The study included 73 women (45 post-menopausal and 28 secondary osteoporotics) and 10 men with established osteoporosis as shown by spinal and femoral bone mineral densities (BMD) > 2 standard deviations (SD) below young normals, and radiological evidence of osteoporosis. MEASUREMENTS: Each patient had routine biochemistry at baseline, an X-ray of thoracic and lumbar spine and a DEXA scan of lumbar spine (L2-L4) and femoral neck. The DEXA scan was repeated following 12 months of therapy. RESULTS: There was no difference between increase in spinal BMD in the post-menopausal (5.7%) versus secondary osteoporotic group (6.7%). There was a significant increase in spinal BMD at 12 months in the 10 male osteoporotics (9.0%, P < 0.01). No overall change in femoral neck BMD was noted. CONCLUSIONS: Cyclical disodium etidronate given with high dose calcium supplements is equally effective in increasing spinal bone mineral density in post-menopausal and secondary osteoporosis. It also results in a significant rise in spinal bone mineral density in male osteoporotics. Whether this produces a reduction in fracture rates is unknown.

Bone Density↗
PubMed1993

Body composition analysis in liver cirrhosis. The measurement of body fat by dual energy X-ray absorptiometry in comparison to skinfold anthropometry, bioelectrical impedance and total body potassium.

In this cross-sectional study of methods to determine total body fat in patients with abnormal body composition secondary to chronic liver disease, we have demonstrated that TBFDXA by four-site skinfold anthropometry was highly correlated to TBFDXA, with small SEE and no bias in patients with ascites, but a small and significant bias in patients without ascites. TBFBIA showed no bias but a weaker correlation with a large SEE. In the presence of fluid retention the correlation coefficient decreased. TBFTBK showed a highly significant bias, and the correlation was not as good as SFA, and decreased in the presence of fluid retention.

Absorptiometry, Photon↗
PubMed1993

Variation in lumbar spine and femoral neck bone mineral measured by dual energy X-ray absorption: a study of 329 normal women.

Reference ranges used in dual energy X-ray absorptiometry (DXA) have previously used piecewise linear fits to the whole data set for spine or femur bone mineral density (BMD) as a function of age. In a study of 329 Caucasian normal women we present a refinement to the normal range by fitting straight lines between quinquennial mean values of BMD for each site measured (lumbar spine, femoral neck and Ward's triangle). From the age of 40 years onwards the premenopausal women demonstrated minimal loss of BMD whereas postmenopausal women showed a rapid loss amounting to 27% in the lumbar spine, 27% in the femoral neck and 38% in the Ward's triangle region in the age range under examination. Comparison of quinquennial means for pre and postmenopausal women in age bands 45-49 years and 50-54 years shows that at these ages postmenopausal BMD is significantly lower than premenopausal BMD (P < 0.05). This finding suggests that separate normal ranges should be used for pre and postmenopausal women. As reduction in the production of oestrogen is a major factor in postmenopausal bone loss and oestrogen function is related to years since menopause (YSM), a more logical way of displaying postmenopausal normal BMD ranges would be in terms of YSM rather than chronological age. Such data are given in this paper.

Absorptiometry, Photon↗
PubMed1992

Bone ultrasonic attenuation in women: reproducibility, normal variation and comparison with photon absorptiometry.

The reproducibility of two methods of measuring broadband ultrasonic attenuation (BUA) in the calcaneus have been studied. An improvement in reproducibility in vivo from 9.6% to 2.8% between old and new techniques has been observed. Measurements of the calcaneus using BUA were correlated with measurements of bone mineral density measured by dual energy x-ray absorptiometry in the lumbar spine, femur and total body and bone mineral content in the distal and proximal forearm measured by single photon absorptiometry. For the older BUA technique the correlation coefficients ranged between r = 0.27 and r = 0.34. For the newer BUA technique the correlation coefficients ranged between r = 0.49 and r = 0.62 and were all significant (P less than 0.001).

Absorptiometry, Photon↗
PubMed1992

Comparison of measures of body composition in a trial of low dose growth hormone replacement therapy.

OBJECTIVE: We assessed the effects of the administration of low dose growth hormone in growth hormone deficient adults on body composition and physical performance. We compared the validity of different measures of body composition in GH treated adults. DESIGN: An uncontrolled longitudinal study of eight patients with GH deficiency who were treated with 4 units of biosynthetic growth hormone (Norditropin), three times a week. Subjects were studied for 8 weeks. PATIENTS: Eight patients with acquired growth hormone deficiency as defined by < 5 mU/l GH following standard provocative investigations in whom other hormone replacement was optimized. MEASUREMENTS: IGF-I was measured on day 1 and after 4 and 8 weeks of treatment with recombinant human growth hormone. Body composition was estimated by dual energy X-ray absorptiometry, bioelectrical impedance, skinfold anthropometry, total body potassium measurement and by computerized tomography of a representative cross-sectional area of thigh on day 1 and following 8 weeks of treatment. Exercise capacity was measured on an electromechanical bicycle and palmar grip strength was measured using a Jamar dynamometer on day 1 and after 8 weeks. RESULTS: IGF-I increased significantly. Exercise capacity and maximum heart rate achieved on the electromechanical bicycle increased significantly. Grip strength did not change. There was a significant increase in fat-free mass and a decline in fat mass as shown by dual energy X-ray absorptiometry and bioelectrical impedance. However, this was not confirmed by other methods. No side-effects were noted. CONCLUSIONS: This study shows that a low dose of biosynthetic growth hormone can elevate IGF-I levels and have a pronounced physical impact in the growth hormone deficient adult without the side-effects seen at higher dosage schedules. Over a 2 month period the increase in fat-free mass may be due to an increase in total body water; however, the decline in fat mass is a genuine effect.

Absorptiometry, Photon↗
PubMed1992

The application of microdosimetry in clinical bone densitometry using a dual-photon absorptiometer.

Experimental microdosimetric methods have been used to determine absorbed dose values for a scanning dual-photon absorptiometer. Absorbed doses within the scanned field have been obtained for three different scanning speeds. For the normal speed setting used clinically, measurements have also been carried out in a water-filled phantom in order to estimate typical patient entrance, exit and midline doses. The results agree well with values obtained using thermoluminescence dosimetry and support the claims of the manufacturers with regard to upper limits placed on patient dose levels. The microdosimetric method enables changes in radiation quality to be followed and comparisons to be made with other low-energy photon fields used in medical diagnosis.

Absorptiometry, Photon↗
PubMed1989

Examination of errors caused by random summing in in vivo prompt gamma ray analysis.

A technique is described for examining the mode of operation of radiation detectors and estimating the losses and gains caused by random summing effects in spectra acquired at high counting rates. The technique is applied to estimating the errors caused by random summing when measuring the amounts of carbon and nitrogen in the human body by the prompt gamma ray neutron activation analysis system installed in Leeds, UK. Our examination shows that the counting rate would have to increase to more than twice the value used at the method's calibration, before an error of greater than 10% is caused in the estimation of carbon by random summing effects, whilst for nitrogen a change of only 18% in the counting rate will cause a 10% error in its estimation.

Activation Analysis↗