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Biomedical subjects

A J Sutton

Publications and source records attributed to A J Sutton.

At least 37 records · Page 2Linked to original sources
PubMed2004

Abdominal aortic aneurysm repair in patients with chronic renal disease.

OBJECTIVES: To assess the outcome of AAA repair in patients with established renal failure (RF), including patients on dialysis. DESIGN: Retrospective case-control study in a teaching hospital. Methods. All patients with established RF undergoing AAA repair were identified during the last eight years. Data was collected from patient notes on operative difficulty, hospital mortality, survival time and future dialysis requirements. For comparison, 28 consecutive patients undergoing AAA repair without RF were studied prospectively. RESULTS: Thirteen RF patients were identified. Three were receiving Continuous Ambulatory Peritoneal Dialysis (CAPD), three were receiving Haemodialysis (HD) and seven had established RF, but were not receiving dialysis. Compared with the control patients, RF patients had a longer total hospital stay (p=0.03, 95% CI for median stay -24.3 to -4.0 days), more postoperative complications (p<0.01, 95% CI 26.4-73.7%) and had an increased in-hospital mortality (p=0.02, 95% CI 4.6-54.3%). Four of the six survivors who were non-dialysis-dependent required long-term dialysis postoperatively. CONCLUSIONS: AAA repair in RF patients is associated with increased postoperative morbidity and mortality. Previously non-dialysis-dependent patients have a high risk of subsequent long-term dialysis.

Aged↗
PubMed2004

Angiotensin receptor blockers as anti-hypertensive treatment for patients with diabetes mellitus: meta-analysis of controlled double-blind randomized trials.

AIMS: To assess the evidence for possible reduction of all-cause mortality, cardiovascular morbidity and mortality, and end-stage renal disease in diabetic patients treated with angiotensin II type 1 receptor blockers (ARBs) as an anti-hypertensive treatment. METHODS: Systematic review and meta-analysis of randomized, double-blind controlled trials of at least 1 year's duration. ARBs were used in the intervention group vs. placebo or standard anti-hypertensive treatment in the control group. The main outcome measures were all-cause mortality, cardiovascular morbidity and mortality, and end-stage renal disease. RESULTS: Three studies fulfilled the inclusion criteria. Separate analyses were conducted for comparisons of ARBs with groups given placebo and those given standard anti-hypertensive treatment. There was no significant difference in mortality between the ARBs and placebo groups, with an estimated odds ratio (OR) of 0.99 [95% confidence interval (CI) 0.81, 1.20]. There was a non-significant difference in patients treated with ARBs compared with standard anti-hypertensive treatment, with an OR of 0.78 (95% CI 0.45, 1.36). No statistically significant difference in cardiovascular morbidity and mortality between the intervention and placebo groups was found, with an OR of 0.91 (95% CI 0.77, 1.08). When ARBs were compared with standard treatment, the OR was estimated at 0.85 (0.54, 1.33). Data on end-stage renal disease were available for two studies comparing ARBs vs. placebo and showed a statistically significant advantage of ARBs, with an OR of 0.73 (95% CI 0.6, 0.89). As only one study compared end-stage renal disease outcome for ARBs vs. standard treatment, a meta-analysis was not possible. This study reported a considerable benefit of ARBs [OR = 0.73 (0.54, 1.01)] compared with the calcium channel blocker amlodipine. CONCLUSIONS: ARBs failed to show significant reduction in total mortality and cardiovascular morbidity and mortality in diabetic patients. The only statistical benefit was the reduction of end-stage renal disease compared with placebo. Therefore, at this time ARBs have not proved to be superior to standard anti-hypertensive treatment in diabetic patients.

Angiotensin II↗
PubMed2003

Reporting of prognostic markers: current problems and development of guidelines for evidence-based practice in the future.

Prognostic markers help to stratify patients for treatment by identifying patients with different risks of outcome (e.g. recurrence of disease), and are important tools in the management of cancer and many other diseases. Systematic review and meta-analytical approaches to identifying the most valuable prognostic markers are needed because (sometimes conflicting) evidence relating to markers is often published across a number of studies. To investigate the practicality of this approach, an empirical investigation of a systematic review of tumour markers for neuroblastoma was performed; 260 studies of prognostic markers were identified, which considered 130 different markers. The reporting of these studies was often inadequate, in terms of both statistical analysis and presentation, and there was considerable heterogeneity for many important clinical/statistical factors. These problems restricted both the extraction of data and the meta-analysis of results from the primary studies, limiting feasibility of the evidence-based approach.Guidelines for reporting the results of primary prognostic marker studies in cancer, and other diseases, are given in order to facilitate both the interpretation of individual studies and the undertaking of systematic reviews, meta-analysis and, ultimately, evidence-based practice. General availability of full individual patient data is a necessary step forward and would overcome the majority of problems encountered, including poorly reported summary statistics and variability in cutoff level, outcome assessed and adjustment factors used. It would also limit the problem of reporting bias, although publication bias will remain a concern until studies are prospectively registered. Such changes in practice would help important evidence-based reviews to be conducted in order to establish the most appropriate prognostic markers for clinical use, which should ultimately improve patient care.

Biomarkers, Tumor↗
PubMed2003

A systematic review of molecular and biological markers in tumours of the Ewing's sarcoma family.

The aims of this study were to perform the first systematic review of molecular and biological tumour markers in tumours of the Ewing's sarcoma family (ESFT), and evaluate the current evidence for their clinical use. A well-defined, reproducible search strategy was used to identify the relevant literature from 1966 to February 2000. Papers were independently assessed for tumour markers used in the screening, diagnosis, prognosis or monitoring of patients with ESFT. Eighty-four papers studying the use of 70 different tumour markers in ESFT's were identified. Low-quality, inconsistent reporting limited meta-analysis to that of prognostic data for 28 markers. Patients with tumours lacking S-100 protein expression have a better overall survival (OS) (hazard ratio (HR)=0.41, 95% confidence interval (CI) 0.19, 0.89) than those with expression; patients with high levels of serum LDH had a worse OS and disease-free survival (DFS) (OS: HR=2.92, CI 2.16, 3.94, DFS: HR=3.38, 95% CI 2.28, 4.99); patients with localised disease and tumours expressing type 1 EWS-FLI1 fusion transcripts had an improved DFS compared with those with other fusion transcript types (HR=0.17, 95% CI 0.079, 0.37). The knowledge base formed should facilitate more informative future research. Improved statistical reporting and large, multicentre prospective studies are advocated.

Biomarkers, Tumor↗
PubMed2003

Suppression of TSH in congenital hypothyroidism is significantly related to serum levels and dosage of thyroxine.

AIM: To assess thyrotropin (thyroid-stimulating hormone; TSH) suppression and serum thyroxine (T(4)) concentrations in infants with congenital hypothyroidism in relation to T(4) dose and pretreatment parameters. METHOD: A retrospective study of all cases treated in a single centre since neonatal screening began was performed. RESULTS: In 54 infants treated with a mean daily T(4) dose of 9.8 microg/kg, the TSH concentration was suppressed (<6 mU/l) in 65% of the cases by 6 months with the serum T(4) level at the upper end of the infant reference range. Infants who suppressed their TSH later did not differ in pretreatment serum TSH or T(4) concentration. T(4) dose and serum T(4) level were lower in infants whose TSH was not suppressed. CONCLUSIONS: TSH suppression in congenital hypothyroidism is significantly related to serum levels and dosage of T(4). We suggest that a delay in TSH suppression is mainly due to undertreatment.

Aging↗
PubMed2002

A comparison of summary patient-level covariates in meta-regression with individual patient data meta-analysis.

OBJECTIVES: To compare meta-analysis of summary study level data with the equivalent individual patient data (IPD) analysis when interest lies in identification of binary patient characteristics related to treatment efficacy. DESIGN: A simulation study comparing meta-regression with IPD analyses of randomized controlled trials. METHODS: Twenty-seven different meta-analysis situations were simulated with 1000 repetitions in each case. The following parameters were varied: (1) the treatment effect magnitude for different patient risk groups; (2) sample sizes of individual studies; and (3) number of studies. The meta-regression and IPD results were then compared for each situation. RESULTS: The statistical power of meta-regression was dramatically and consistently lower than that of IPD analysis, with little agreement between the parameter estimates obtained from the two methods. Only in meta-analyses of large numbers of large trials, did meta-regression detect differential treatment effects between risk groups with any consistency. CONCLUSIONS: Meta-analysis of summary data may be adequate when estimating a single pooled treatment effect or investigating study level characteristics. However, when interest lies in investigating whether patient characteristics are related to treatment, IPD analysis will generally be necessary to discover any such relationships. In these situations practitioners should try to obtain individual-level data.

Humans↗
PubMed2002

A meta-analysis of 50 years of ruptured abdominal aortic aneurysm repair.

BACKGROUND: Operative repair of ruptured abdominal aortic aneurysm (RAAA) is associated with a high mortality rate but reported figures vary widely. The aim of this study was to estimate the operative mortality of RAAA repair and determine how it has changed over time. METHODS: A meta-analysis of all English language literature quoting figures for operative mortality of RAAA repair. RESULTS: The pooled estimate for the overall operative mortality rate of RAAA repair from 1955 to 1998 was 48 (95 per cent confidence interval 46 to 50) per cent. Meta-regression analysis of operative mortality over time demonstrated a constant reduction of approximately 3.5 per cent per decade (1954-1997) with an operative mortality rate estimate for the year 2000 of 41 per cent. Seventy-seven studies reported intraoperative mortality but, while this appears to have remained constant over time, there was evidence of the presence of publication bias in the subgroup of papers reporting this outcome. There was no evidence of publication bias for the overall operative mortality outcome. CONCLUSION: Contrary to the conclusion of recent studies, this paper demonstrates a gradual reduction with time in the operative mortality rate of RAAA repair.

Aged↗
PubMed2002

Decision analytical economic modelling within a Bayesian framework: application to prophylactic antibiotics use for caesarean section.

Economic evaluation of health care interventions based on decision analytic modelling can generate valuable information for health policy decision makers. However, the usefulness of the results obtained depends on the quality of the data input into the model; that is, the accuracy of the estimates for the costs, effectiveness, and transition probabilities between the different health states of the model. The aim of this paper is to review the use of Bayesian decision models in economic evaluation and to demonstrate how the individual components required for decision analytical modelling (i.e., systematic review incorporating meta-analyses, estimation of transition probabilities, evaluation of the model, and sensitivity analysis) may be addressed simultaneously in one coherent Bayesian model evaluated using Markov Chain Monte Carlo simulation implemented in the specialist Bayesian statistics software WinBUGS. To illustrate the method described, a simple probabilistic decision model is developed to evaluate the cost implications of using prophylactic antibiotics in caesarean section to reduce the incidence of wound infection. The advantages of using the Bayesian statistical approach outlined compared to the conventional classical approaches to decision analysis include the ability to: (i) perform all necessary analyses, including all intermediate analyses (e.g., meta-analyses) required to derive model parameters, in a single coherent model; (ii) incorporate expert opinion either directly or regarding the relative credibility of different data sources; (iii) use the actual posterior distributions for parameters of interest (opposed to making distributional assumptions necessary for the classical formulation); and (iv) incorporate uncertainty for all model parameters.

Antibiotic Prophylaxis↗
PubMed2001

An illustrated guide to the methods of meta-analysis.

Meta-analysis is now accepted as a necessary tool for the evaluation of health care. Such analyses have been carried out in virtually every area of medicine to evaluate a wide spectrum of health care interventions and policies. This paper has three broad aims: (1) to describe the basic principles of meta-analysis, using a meta-analysis of interventions intended to reduce hospital re-admission rates for illustration; (2) to consider threats to the internal validity of meta-analysis, and the measures which can be taken to minimize their impact; and (3) to present an overview of more specialist and developing methods for synthesizing data, with the intention of outlining the directions meta-analysis may take in the future. The methods used to synthesize studies, which take 'weighted averages' of effect sizes have been refined to a high degree, while the methods for dealing with threats to the validity of meta-analyses such as publication bias, and variations in quality of the primary studies, are at a less advanced stage. However, many consider this standard 'weighted average' approach to meta-analysis not to be 'state of the art' in at least some situations, where the use of more sophisticated methods, generally to explain variation in estimates from different studies and synthesize a broader base of evidence, would be advantageous. Currently, approaches which attempt to do this are mainly still in the experimental stage and, unfortunately, ideas which sound natural and appealing are often difficult to implement in practice. Clearly, it will be some time before they are used routinely, but significant steps have been made.

Bayes Theorem↗
PubMed2001

Discoloration of a titanium alloy removable partial denture: a clinical report.

With recent advances in dental technology, titanium is currently used for fabrication of crowns, fixed partial dentures, implant frameworks, and removable partial denture frameworks. The use of titanium-aluminum-vanadium (Ti-6Al-4V) alloy assumes that it imparts similar anti-corrosion characteristics to the commercially pure titanium. This clinical report describes a patient who experienced discoloration of a Ti-6Al-4V alloy removable partial denture.

Alloys↗
PubMed2001

A case-control study to investigate the relation between low and moderate levels of physical activity and osteoarthritis of the knee using data collected as part of the Allied Dunbar National Fitness Survey.

BACKGROUND: Physical activity is being recommended as an intervention for seemingly almost universal improvements to health. A potential concern with this recommendation for increased exercise is that some believe increased levels of activity may lead to increased incidence of osteoarthritis of the knee (knee OA), as a result of accelerated "wear and tear" of the major joints. OBJECTIVE: To investigate the hypothesis that the occurrence of knee OA may be related to the duration of participation in some forms of sport and active recreation. METHODS: The relation between habitual exercise, reported by a cross section of people surveyed in England, and self reported knee OA was investigated. Data were derived from the Allied Dunbar National Fitness Survey (1990-91). A matched retrospective case-control design was used and a new exposure classification system which categorised different grades of activities for different time periods for each subject's lifetime participation in regular physical activities was developed. Additional data on knee injuries sustained and bodily composition were also included in a multivariate analysis. RESULTS: From 4316 people originally interviewed, 216 eligible cases (66 men, 150 women) were identified (mean age 57.1). Each case was matched to four controls. When habitual sport/exercise participation were examined during a subject's life, only exposure to regular long walks and being physically active between the ages of 20 and 24 suggested any association with developing knee OA later in life. The only strong association found was a greatly increased risk of knee OA having previously sustained a knee injury (p<0.01, odds ratio 8.0 (95% confidence interval 2.0 to 32.0)). CONCLUSIONS: There was little evidence to suggest that increased levels of regular physical activity throughout life lead to an increased risk of knee OA later in life. Previous knee injury was associated with an increased risk of knee OA. Additionally, most injuries were caused through participation in physical activities. Hence, when deciding on participation in activities, it is worth taking the likelihood of joint injury into consideration, as the chance of injury is greater in some activities than others.

Adolescent↗
PubMed2001

Methods for exploring heterogeneity in meta-analysis.

In meta-analysis, when the difference in results between studies is greater than would be expected by chance, one needs to investigate whether the observed variation in results across studies is associated with clinical and/or methodological differences between studies. This article reviews methods used in meta-analysis for exploring heterogeneity, including statistical tests for homogeneity, methods for visually displaying results of primary studies, methods for reducing heterogeneity, methods for investigating sources of heterogeneity, and identification of moderator variables or effect modifiers. The investigation of sources of heterogeneity in meta-analysis is by nature exploratory, and therefore its results should always be interpreted with caution. However, careful investigation of heterogeneity may provide an important second level of evidence that can be useful in suggesting direction of future research. Sometimes, it may provide clinically important results by indicating who might benefit more or less from a treatment or how an intervention should be applied.

Data Interpretation, Statistical↗
PubMed2001

Bayesian methods in meta-analysis and evidence synthesis.

This paper reviews the use of Bayesian methods in meta-analysis. Whilst there has been an explosion in the use of meta-analysis over the last few years, driven mainly by the move towards evidence-based healthcare, so too Bayesian methods are being used increasingly within medical statistics. Whilst in many meta-analysis settings the Bayesian models used mirror those previously adopted in a frequentist formulation, there are a number of specific advantages conferred by the Bayesian approach. These include: full allowance for all parameter uncertainty in the model, the ability to include other pertinent information that would otherwise be excluded, and the ability to extend the models to accommodate more complex, but frequently occurring, scenarios. The Bayesian methods discussed are illustrated by means of a meta-analysis examining the evidence relating to electronic fetal heart rate monitoring and perinatal mortality in which evidence is available from a variety of sources.

Bayes Theorem↗
PubMed2000

Systematic review of water fluoridation.

OBJECTIVE: To review the safety and efficacy of fluoridation of drinking water. DESIGN: Search of 25 electronic databases and world wide web. Relevant journals hand searched; further information requested from authors. Inclusion criteria were a predefined hierarchy of evidence and objectives. Study validity was assessed with checklists. Two reviewers independently screened sources, extracted data, and assessed validity. MAIN OUTCOME MEASURES: Decayed, missing, and filled primary/permanent teeth. Proportion of children without caries. Measure of effect was the difference in change in prevalence of caries from baseline to final examination in fluoridated compared with control areas. For potential adverse effects, all outcomes reported were used. RESULTS: 214 studies were included. The quality of studies was low to moderate. Water fluoridation was associated with an increased proportion of children without caries and a reduction in the number of teeth affected by caries. The range (median) of mean differences in the proportion of children without caries was -5.0% to 64% (14.6%). The range (median) of mean change in decayed, missing, and filled primary/permanent teeth was 0.5 to 4.4 (2.25) teeth. A dose-dependent increase in dental fluorosis was found. At a fluoride level of 1 ppm an estimated 12.5% (95% confidence interval 7.0% to 21.5%) of exposed people would have fluorosis that they would find aesthetically concerning. CONCLUSIONS: The evidence of a beneficial reduction in caries should be considered together with the increased prevalence of dental fluorosis. There was no clear evidence of other potential adverse effects.

Child↗
PubMed2000

Empirical assessment of effect of publication bias on meta-analyses.

OBJECTIVE: To assess the effect of publication bias on the results and conclusions of systematic reviews and meta-analyses. DESIGN: Analysis of published meta-analyses by trim and fill method. STUDIES: 48 reviews in Cochrane Database of Systematic Reviews that considered a binary endpoint and contained 10 or more individual studies. MAIN OUTCOME MEASURES: Number of reviews with missing studies and effect on conclusions of meta-analyses. RESULTS: The trim and fill fixed effects analysis method estimated that 26 (54%) of reviews had missing studies and in 10 the number missing was significant. The corresponding figures with a random effects model were 23 (48%) and eight. In four cases, statistical inferences regarding the effect of the intervention were changed after the overall estimate for publication bias was adjusted for. CONCLUSIONS: Publication or related biases were common within the sample of meta-analyses assessed. In most cases these biases did not affect the conclusions. Nevertheless, researchers should check routinely whether conclusions of systematic reviews are robust to possible non-random selection mechanisms.

Clinical Trials as Topic↗
PubMed2000

Custom retainer for the Blom-Singer adjustable tracheostoma valve.

This article presents a procedure that allows the laryngectomy patient to be fitted with a well-sealed custom device. The custom device provides near-normal speech during a variety of activities. The custom retainer for the Blom-Singer adjustable tracheostoma valve can be fabricated with medical grade silicone using routine prosthodontic techniques.

Biocompatible Materials↗