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Biomedical subjects

B Reeves

Publications and source records attributed to B Reeves.

At least 37 records · Page 2Linked to original sources
PubMed1999

Evaluating the outcomes of low vision rehabilitation.

The requirement for those providing healthcare to measure outcomes raises the fundamental question of how these should be measured. Both the scale of the low vision population and the different models of care proposed make it a pressing need to determine outcomes using valid and reliable measures. In this study we describe the development and piloting of a questionnaire designed to meet this requirement. The questionnaire was piloted on 56 subjects with age-related macular degeneration (ARMD). Test-retest reliability of the questionnaire was estimated using a further sample of 28 subjects with ARMD. Pilot testing confirmed the feasibility of administering the questionnaire to an elderly population with ARMD. A total of 87% of the sample reported using an LVA (65% on a daily basis), predominantly for a reading task. The number of tasks an LVA was used for, its frequency of use, length of continuous use and ease of use are significantly associated with the rating of an LVA as important/less important (P < 0.0001), but the acuity achieved with the device is not significantly associated with rated importance (P = 0.11), reinforcing doubt about the validity of visual function outcomes. The limitations of this pilot study and earlier case series in describing the outcomes of low vision care are discussed and a randomised controlled trial using a broad range of outcomes is proposed in order to fully describe the effectiveness of low vision rehabilitation and inform the debate about models of care.

Aged↗
PubMed1999

Compliance with methodological standards when evaluating ophthalmic diagnostic tests.

PURPOSE: To draw attention to the importance of methodological standards when carrying out evaluations of ophthalmic diagnostic tests by reviewing the extent of compliance with these standards in reports of evaluations published within the ophthalmic literature. METHODS: Twenty published evaluations of ophthalmic screening/diagnostic tests or technologies were independently assessed by two reviewers for compliance with the following methodological standards: specification of the spectrum composition for populations used in the evaluation, analysis of pertinent subgroups, avoidance of work-up (verification) bias, avoidance of review bias, presentation of precision of results for test accuracy, presentation of indeterminate test results, and presentation of test reproducibility. RESULTS: Compliance ranged from just 10% (95%CI, 1%-32%) for presentation of test reproducibility data and avoidance of review bias to 70% (95%CI, 46%-88%) for avoidance of work-up bias and presentation of indeterminate test results. Only 5 of the 20 evaluations complied with four or more of the methodological standards and none with more than five of the standards. CONCLUSIONS: The evaluations of ophthalmic diagnostic tests discussed in this article show limited compliance with accepted methodological standards but are no worse than previously described for evaluations published in general medical journals. Adherence to these standards by researchers can improve the study design and reporting of evaluations of new diagnostic techniques. Limited compliance, combined with a lack of awareness of the standards among users of research evidence, may lead to the inappropriate adoption of new diagnostic technologies, with a consequent waste of health care resources.

Bias↗
PubMed1998

Point of care testing: randomised controlled trial of clinical outcome.

OBJECTIVES: To describe the proportion of patients attending an accident and emergency department for whom blood analysis at the point of care brought about a change in management; to measure the extent to which point of care testing resulted in differences in clinical outcome for these patients when compared with patients whose samples were tested by the hospital laboratory. DESIGN: Open, single centre, randomised controlled trial. Blood samples were randomly allocated to point of care testing or testing by the hospital's central laboratory. SETTING: The accident and emergency department of the Bristol Royal Infirmary, a large teaching hospital which cares for an inner city population. SUBJECTS: Representative sample of patients who attended the department between April 1996 and April 1997 and who required blood tests. Data collection was structured in 8 hour blocks so that all hours of the day and all days of the week were equally represented. MAIN OUTCOME MEASURES: The proportion of patients for whom point of care testing brought about a change in treatment in which timing was considered to be critical to clinical outcome. Mortality, the length of stay in hospital, admission rate, the amount of time spent waiting for results of blood tests, the amount of time taken to decide on management plans, and the amount of time patients spent in the department were compared between patients whose samples were tested at the point of care and those whose samples were sent to the laboratory. RESULTS: Samples were obtained from 1728 patients. Changes in management in which timing was considered to be critical occurred in 59 out of 859 (6.9%, 95% confidence interval 5.3% to 8.8%) patients in the point of care arm of the trial. Decisions were made 74 minutes earlier (68 min to 80 min, P < 0.0001) when point of care testing was used for haematological tests as compared to central laboratory testing, 86 minutes earlier (80 min to 92 min, P < 0.0001) for biochemical tests, and 21 minutes earlier (-3 min to 44 min, P = 0.09) for analyses of arterial blood gases. There were no differences between the groups in the amount of time spent in the department, length of stay in hospital, admission rates, or mortality. CONCLUSION: Point of care testing reduced the time taken to make decisions on patient management that were dependent on the results of blood tests. It also brought about faster changes in treatment for which timing was considered to be critical in about 7% of patients. These changes did not affect clinical outcome or the amount of time patients spent in the department.

Adult↗
PubMed1998

Hemodynamic performance of the 21-mm St. Jude BioImplant prosthesis using dobutamine Doppler echocardiography.

This study examines the hemodynamic performance of small size St. Jude BioImplant aortic prostheses using dobutamine echocardiography. Eleven patients (3 women, mean age 75 years) who had undergone aortic valve replacement with a size 21-mm St. Jude BioImplant aortic prostheses at 10.8 +/- 5.1 months (SD) previously were studied. Dobutamine infusion was started at a rate of 5 microg/kg/min and increased to 10 microg/kg/min, and subsequently to 20 microg/kg/min at 15-minute intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area, mean gradient, and the performance index across each prosthesis were calculated and cardiac output was determined by Doppler measurement of flow in the left ventricular outflow tract. Stress dobutamine increased heart rate and cardiac output by 51% and 56%, respectively (both p <0.0001), and the mean transvalvular gradient increased from 30.1 +/- 7.5 mm Hg at rest to 49.3 +/- 11.5 mm Hg at maximum stress (p <0.0005). The performance index increased progressively from 0.29 +/- 0.05 at rest to 0.40 +/- 0.10 at maximum stress (p <0.0005). Regression modeling analyses demonstrated that the maximum stress gradient was independent of all variables except the resting gradient (p = 0.03). Body surface area had no effect on the changes in cardiac output, effective orifice area, or transprosthetic gradient at maximum stress. Thus, these data demonstrate that the size 21-mm St. Jude BioImplant prosthesis exhibits suboptimal hemodynamic performance with transvalvular gradients consistent with mild to moderate aortic stenosis, both at rest and under stress conditions.

Adrenergic beta-Agonists↗
PubMed1997

Dynamic evaluation of the 21-mm Medtronic Intact aortic bioprosthesis by dobutamine echocardiography.

BACKGROUND: High residual transvalvular gradients have been reported with the use of small Medtronic Intact aortic valve prostheses. The aim of this study was to evaluate the hemodynamic performance of 21-mm prostheses using dobutamine Doppler echocardiography. METHODS: Ten patients (7 women; mean age, 79 years) who had undergone aortic valve replacement with 21-mm Medtronic Intact prostheses 19.1 +/- 9.9 (standard deviation) months previously were studied. Dobutamine infusion was started at a rate of 5 microg x kg(-1) x min(-1) and increased to 10 and 20 microg x kg(-1) x min(-1) at 15-minute intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area, performance index, and discharge coefficient of each valve were calculated, and peak and mean velocity and pressure drop across the prostheses were measured. Cardiac output was determined by Doppler measurement of flow in the left ventricular outflow tract. RESULTS: Dobutamine stress increased heart rate and cardiac output by 68% and 65%, respectively (both p < 0.005), and mean transvalvular gradient increased from 19.1 +/- 5.1 mm Hg at rest to 33.2 +/- 7.7 mm Hg at maximum stress (p < 0.0001). Regression analyses demonstrated that maximum-stress gradient was independent of all variables except resting gradients (p < 0.004). Body surface area had no effect on the changes in cardiac output, effective orifice area, or transprosthetic gradient at maximum stress. CONCLUSIONS: These data show that the 21-mm Medtronic Intact aortic prosthesis exhibits acceptable hemodynamic performance. Transvalvular gradients remained within a clinically acceptable range, both at rest and at maximum stress. Moreover, overall hemodynamic performance suggests that patient-prosthesis mismatch is unlikely to be a problem of clinical importance when this prosthesis is used.

Aged↗
PubMed1997

Cardiac troponin T and troponin I release during coronary artery surgery using cold crystalloid and cold blood cardioplegia.

OBJECTIVE: To evaluate and compare myocardial protection using cold crystalloid and blood cardioplegia by measuring release of cardiac Troponin T and Troponin I during coronary artery surgery. METHODS: Forty two patients undergoing myocardial revascularization were prospectively randomised into two groups in whom myocardial protection was achieved with either antegrade cold (4 degrees C) crystalloid (CCP) (n = 21) St. Thomas' I cardioplegic solution. Serial venous blood samples were collected for measurement of cardiac Troponin T and Troponin I, prior to induction of anesthesia and at 4, 12, 24 and 48 h after removal of the aortic cross clamp. RESULTS: There were no hospital deaths in the two groups and one patient in each group suffered a perioperative myocardial infarction. Rising levels of Troponin T and Troponin I were found in all patients. Serum concentrations increased as early as 4 h after removal of the aortic cross clamp, and reached a peak at 12 h postoperatively in both groups. These levels subsequently declined, but remained higher than preoperative values at 48 h. There were no differences between the two groups with respect to serum Troponin T and I release at 4, 12, 24 and 48 h, area under the respective curves, and peak Troponin T and I release. Serum Troponin levels were significantly higher in patients with unstable angina and in two patients who suffered a perioperative myocardial infarction. CONCLUSION: Serum release of cardiac Troponin T and Troponin I is significantly raised in low risk patients undergoing myocardial revascularization. This release is similar when either cold crystalloid or cold blood cardioplegia are used. This may imply that both methods offer identical protection to the myocardium in a low risk group of patients.

Aged↗
PubMed1997

Cytogenetics and prognosis in childhood lymphoblastic leukaemia: results of MRC UKALL X. Medical Research Council Working Party in Childhood Leukaemia.

We have analysed the prognostic influence of cytogenetic findings at diagnosis in a group of 502 children with acute lymphoblastic leukaemia (ALL), treated on MRC UKALL X, in whom clonal cytogenetic abnormalities were detected at diagnosis. Despite the overall improvement in outcome in children treated on this protocol compared with previous trials, some cytogenetically-defined groups were still associated with a poor outcome and ploidy retained some prognostic significance. Patients with high hyperdiploid ALL (39% of those with clonal abnormalities) had a favourable outcome with event free survival of 71% at 5 years. Those with near haploidy (1%), hypodiploidy (9%) and low hyperdiploidy (16.5%) had a relatively poor prognosis with event-free survival at 5 years of 17%, 42% and 49% respectively. Only two of 12 children with Ph-positive leukaemia are alive in remission and abnormalities of chromosome 11q23 were also associated with a high risk of treatment failure. In contrast, the t(1;19) was associated with improved event-free survival of 87.5% at 5 years. A number of other non-random abnormalities were identified with no clear prognostic significance. We conclude that identification of certain genetic changes remains important in the management of acute lymphoblastic leukaemia, although whether molecular diagnosis of clinically relevant abnormalities can now supplant cytogenetics in the clinical trials context remains to be determined.

Child↗
PubMed1997

Hemodynamics of St. Jude Medical prostheses in the small aortic root: in vivo studies using dobutamine Doppler echocardiography.

BACKGROUND AND AIMS OF THE STUDY: The well known correlation between prosthetic valve orifice area and transvalvular pressure drop has raised concerns about the presence of significant residual gradients when only a small-sized prosthesis can be implanted, particularly in patients with a large body surface area. The aim of this study was to study the hemodynamic performance of small-size St. Jude Medical aortic prostheses using dobutamine echocardiography. METHODS: Fifteen patients (14 females, one male, of mean age 67 years) who had undergone aortic valve replacement with size 19 mm St. Jude Medical prostheses at a mean of 19 +/- 8 (SD) months previously were studied. Dobutamine infusion was started at a rate of 5 micrograms/kg/min and increased to 10 and subsequently to 20 micrograms/kg/min at 15-min intervals. Pulsed and continuous-wave Doppler studies were performed at rest and at the end of each stage. Effective orifice area (EOA) and mean gradient across each prosthesis were calculated, and cardiac output (CO) was determined by Doppler measurement of flow in the left ventricular outflow tract. RESULTS: Dobutamine-stress increased heart rate and cardiac output by 57% and 86% respectively (both p < 0.0005), and mean transvalvular gradient increased from 22.0 +/- 4.9 mmHg at rest to 41.9 +/- 9 mmHg at maximum stress (p < 0.0001). Regression modeling analyses demonstrated that maximum stress gradient was independent of all variables except resting gradient (p = 0.0068). Body surface areas had no effect on the changes in cardiac output, effective orifice area or transprosthetic gradient at maximum stress. CONCLUSIONS: These data demonstrate that the size 19 mm St. Jude Medical prosthesis exhibits favorable hemodynamic performance. Transvalvular gradients remained within a clinically acceptable range, both at rest and under stress conditions. Moreover, in the patient population studied, overall hemodynamic performance indicates that with St. Jude Medical aortic valves, patient-prosthesis mismatch is unlikely to be a problem of clinical importance.

Adult↗
PubMed1996

Influence of external stent size on early medial and neointimal thickening in a pig model of saphenous vein bypass grafting.

BACKGROUND: Late saphenous vein graft failure results from intimal and medial thickening due to migration and proliferation of vascular smooth muscle cells and superimposed atheroma. These changes may represent an adaptation by the vein to its insertion into the arterial system. Using a porcine model of arteriovenous bypass grafting, we recently demonstrated that supporting the graft with a nonrestrictive external Dacron velour stent significantly reduced intimal hyperplasia and total wall thickness. In the present study, we investigated the influence of different external stent sizes on graft wall dimensions and cell proliferation. METHODS AND RESULTS: Three stent sizes were tested: mildly restrictive, nonrestrictive, and oversized (5, 6, and 8 mm in diameter, respectively). Four weeks after grafting, total wall thickness was decreased 40% by 5-mm stents (P = .02), 66% by 6-mm stents (P = .0004), and 81% by 8-mm stents (P = .02 versus unstented grafts). Neointimal thickness was reduced almost 62% by 6-mm and 72% by 8-mm stents (both P = .01) but not by 5-mm stents. As a result, the encroachment of the intima into the lumen was reduced approximately 70% by 6- or 8-mm stents (P = .02 and P = .01 versus unstented grafts, respectively). Both neointimal and medial cell proliferation were significantly reduced by all three stents compared with unstented grafts. CONCLUSIONS: External stenting of saphenous vein bypass grafts reduces early intimal and medial hyperplasia. Oversized stents give equally profound suppression of intimal thickening, obviating the need for precise size matching with the graft and greatly simplifying the surgical procedure.

Animals↗
PubMed1994

The effectiveness of vision screening by school nurses in secondary school.

Vision screening of 13 and 15 year old children by school nurses in Oxfordshire has declined in recent years due to the pressure of other commitments. A study was carried out to evaluate the likely consequences of failing to provide vision screening for secondary schoolchildren, in order to make a decision about the future of the service. Parents were also asked to complete a questionnaire about their children's past eye histories. Eight schools that had had no vision screening for at least three years participated in the study. Overall, 3.8% of children between 13 and 15 years old had a visual acuity of worse than 6/12 in one or both eyes, that is they failed vision screening; there was no evidence that this percentage increased significantly across this age range. Less than 1% of children were prescribed and wore spectacles as a consequence of failing vision screening and no new cases of eye pathology were detected. Questionnaire responses suggested that about 50% of children who did not wear spectacles had had an eye examination in the previous two years. The results indicate that vision screening is not the best way to meet the eye/vision needs of secondary schoolchildren. Strategies for targeting the school nursing resource more appropriately are being considered.

Adolescent↗
PubMed1994

Acute angle closure glaucoma: relative failure of YAG iridotomy in affected eyes and factors influencing outcome.

The treatment of acute angle closure glaucoma has been influenced by the development of the YAG laser and its ability to perform iridotomies as an outpatient procedure. In this retrospective study the results of YAG iridotomy were compared with surgical peripheral iridectomy. When compared with surgical peripheral iridectomy patients, YAG iridotomy patients were at greater risk of proceeding to further surgery, with this risk being significantly associated with increasing duration of attack. The authors suggest that in selected cases, surgical iridectomy should be given consideration as a primary procedure.

Acute Disease↗
PubMed1993

Ocular and vision defects in preschool children.

Ocular and/or vision defects are one of the commonest reasons for the referral of young children to hospital. In a survey of a birth cohort in one health district, 7.1% of children were diagnosed as having such defects by their fifth birthday; 2.1% were detected before the age of 2 years, and 5.1% between 2 and 5 years. Up to the age of 2 years, low birthweight children and those who require postnatal special care had a higher risk of having an ocular or vision defect diagnosed and were more likely to have serious visual impairment than other children. In contrast, between the ages of 2 and 5 years of age these high risk children showed no continuing increased risk of having a defect diagnosed, nor did they show any differences in the severity or type of vision defects compared with other children. Averaged over the years studied, the incidence of defects presenting to specialist eye clinics among all 2-5 year olds was 1.7%, higher than the 1.1% found for 0-2 year olds. This increase consisted primarily of children with refractive errors only.

Child, Preschool↗
PubMed1992

Chromosome 11q23 translocations in both infant and adult acute leukemias are detected by in situ hybridization with a yeast artificial chromosome.

The yeast artificial chromosome (YAC-13HH4), which spans a 440-kb region of DNA just distal to the CD3 locus on chromosome 11 at band q23, has been used to characterize a range of chromosomal translocations in acute leukemias from both adults and infants. In situ hybridization was performed on metaphase cells from bone marrow of 17 leukemias and two cell lines with a variety of chromosome 11q23 abnormalities. It was established that in infant leukemias the translocations t(11;19), t(4;11), and t(5;11) had occurred in the region defined by YAC 13HH4. Additionally, the translocations t(4;11), t(6;11), t(9;11), t(X;11), and t(10;11) in other leukemias were found to disrupt the same region of chromosome 11q23, although an exception was found in one t(6;11) translocation for which the breakpoint was distal to the YAC. One patient had a t(9;11) translocation in a therapy-related leukemia, suggesting that this class of etoposide-related malignancy has similar breakpoints to those occurring in de novo leukemias. An example of a lymphoma-derived translocation t(4;11) was shown to involve a deletion of the region defined by YAC 13HH4. A leukemia with a deletion on chromosome 11 (q23-q25) was also studied and it was shown that the YAC sequence was unaffected. It was concluded that, with a few exceptions, the translocations at 11q23 in a wide range of acute infant and adult leukemias occur in a common region and may result from a common underlying mechanism.

Acute Disease↗
PubMed1992

Possible evidence for genomic imprinting in childhood acute myeloblastic leukaemia associated with monosomy for chromosome 7.

Monosomy or deletion of chromosome 7 is a frequent finding in both de novo and secondary acute myeloid leukaemia (AML) and myelodysplastic syndromes (MDS). Based on analysis of deletions of chromosome 7 in such patients, it has been suggested that there is a critical region of the chromosome lying within bands q21-q31. We have examined bone marrow and peripheral blood samples from 10 patients with MDS, AML and biphenotypic acute leukaemia who had monosomy for or rearrangement of chromosome 7, seeking evidence of non-random allele loss that might suggest the presence of imprinted genes on the chromosome. Bone marrow cells from one patient with the infant monosomy 7 syndrome had loss of maternal alleles as did two patients with biphenotypic leukaemia. Five out of five patients with MDS and both patients with de novo AML had loss of paternal alleles. One of the latter patients had a del(7) (q31q36) rather than monosomy 7. These findings suggest that imprinting of a gene(s) on chromosome 7, within the bands q31-q36, may be of importance in MDS and AML. Despite the reported increased incidence of AML amongst relatives of patients with cystic fibrosis (CF) the gene for which lies in chromosome region 7q31, none of the patients nor parents studied here appeared to be carriers of the most common gene mutation seen in patients with CF, the delta F508.

Acute Disease↗
PubMed1992

Orthoptists reduce false-positive hospital referrals.

This paper describes changes in the pattern of new referrals of children from birth to 2 years-of-age to the Hospital Eye Service in Oxford, following the implementation of a community-based orthoptic secondary vision-screening programme. The findings show that the number of false positive referrals was reduced by a half following the introduction of the service; false-positive referrals were also discharged sooner. This paper reports the findings of this survey and the results demonstrate the cost-effectiveness of the programme compared to outpatient attendance.

Community Health Services↗