Biomedical subjects
Publications and source records attributed to A J Sutton.
Several conditions necessitate surgical or prosthetic ear reconstruction. If an auricular prosthesis is planned, accurate impressions of both the affected and unaffected ears are essential. This article describes a technique that uses a wax-customized, rigid impression tray and irreversible hydrocolloid to minimize distortion during the procedure.
Improved fit is one advantage of a custom ocular prosthesis. Numerous methods exist to gain intimate tissue adaptation. This article reviews the literature concerning such methods and presents an improved technique for fabrication of a custom ocular impression tray.
Meta-analysis is now a widely used technique for summarizing evidence from multiple studies. Publication bias, the bias induced by the fact that research with statistically significant results is potentially more likely to be submitted and published than work with null or non-significant results, poses a threat to the validity of such analyses. The implication of this is that combining only the identified published studies uncritically may lead to an incorrect, usually over optimistic, conclusion. How publication bias should be addressed when carrying out a meta-analysis is currently a hotly debated subject. While statistical methods to test for its presence are starting be used, they do not address the problem of how to proceed if publication bias is suspected. This paper provides a review of methods, which can be employed as a sensitivity analysis to assess the likely impact of publication bias on a meta-analysis. It is hoped that this will raise awareness of such methods, and promote their use and development, as well as provide an agenda for future research.
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OBJECTIVE: To systematically review methods for systematic review/meta-analysis in order to identify the different methodological and statistical methods that have been proposed. A summary of the main findings is presented here, with emphasis given to health services research topics. METHODS: A thorough systematic search for methodological papers was carried out using a variety of methods, including the use of electronic databases. Approximately 1000 potentially relevant references were identified, a number of them from education, psychology and sociology. RESULTS: After briefly reviewing the procedural methods required to carry out a review, and the basic statistical methods used to combine study estimates, less established methods are discussed. These include methods for dealing with publication bias, meta-regression, meta-analysis of individual patient data, the synthesis of non-randomized evidence alone and in combination with randomized studies. Bayesian modelling and economic evaluation through meta-analysis. Recommendations for meta-analytical practice are given; these are either distilled from previous guidelines, or constructed where there appears to be a broad consensus across the literature. CONCLUSIONS: It is hoped that this review will provide a consistent and comprehensive, but concise, description of the methods available for synthesizing evidence, that it will promote better quality reviews of the results of health services research and identify specific areas which require methodological development.
The nematode Caenorhabditis elegans responds to overcrowding and scarcity of food by arresting development as a dauer larva, a nonfeeding, long-lived, stress-resistant, alternative third-larval stage. Previous work has shown that mutations in the genes daf-2 (encoding a member of the insulin receptor family) and age-1 (encoding a PI 3-kinase) result in constitutive formation of dauer larvae (Daf-c), increased adult longevity (Age), and increased intrinsic thermotolerance (Itt). Some daf-2 mutants have additional developmental, behavioral, and reproductive defects. We have characterized in detail 15 temperature-sensitive and 1 nonconditional daf-2 allele to investigate the extent of daf-2 mutant defects and to examine whether specific mutant traits correlate with each other. The greatest longevity seen in daf-2 mutant adults was approximately three times that of wild type. The temperature-sensitive daf-2 mutants fell into two overlapping classes, including eight class 1 mutants, which are Daf-c, Age, and Itt, and exhibit low levels of L1 arrest at 25.5 degrees. Seven class 2 mutants also exhibit the class 1 defects as well as some or all of the following: reduced adult motility, abnormal adult body and gonad morphology, high levels of embryonic and L1 arrest, production of progeny late in life, and reduced brood size. The strengths of the Daf-c, Age, and Itt phenotypes largely correlated with each other but not with the strength of class 2-specific defects. This suggests that the DAF-2 receptor is bifunctional. Examination of the null phenotype revealed a maternally rescued egg, L1 lethal component, and a nonconditional Daf-c component. With respect to the Daf-c phenotype, the dauer-defective (Daf-d) mutation daf-12(m20) was epistatic to daf-2 class 1 alleles but not the severe class 2 alleles tested. All daf-2 mutant defects were suppressed by the daf-d mutation daf-16(m26). Our findings suggest a new model for daf-2, age-1, daf-12, and daf-16 interactions.
OBJECTIVE: To investigate the effect of smoking on the development of systemic lupus erythematosus (SLE), and the association between alcohol consumption and the disease. METHODS: 450 subjects (150 SLE patients and 300 controls) from Nottingham, UK were interviewed in a case-control study. Controls were matched to cases for age and sex. All patients met at least four of the American Rheumatology Association criteria for SLE. Controls were randomly selected from the Nottingham Family Health Services Authority register. Information was collected by interview administered questionnaire concerning demographic variables, smoking histories, and drinking habits. RESULTS: Analysis of the data by conditional logistic regression revealed current smokers to have a significantly increased risk of development of SLE compared with never smokers (odds ratio (OR) 1.95, 95% confidence intervals (CI) 1.14, 3.31), although ex-smokers were not at increased risk. There was also suggestion of a marked, highly significant negative association between SLE and alcohol consumption, the magnitude of which increased with units consumed. CONCLUSIONS: This study suggests that current smokers are at increased risk of developing SLE compared with non-smokers and ex-smokers. In contrast, alcohol consumption seems to be negatively associated with the disease.
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An epigastric impedance technique was used to measure gastric emptying in nonpregnant women, women in the third trimester of pregnancy, and women within 60 min of delivery. The basis of the technique is the increase in epigastric impedance after the ingestion of a nonionic fluid. The subsequent decline in impedance is used as a measure of gastric emptying. The impedance epigastrograph used consisted of a four-electrode array (two source, two detector) that was applied over the epigastrium. The method was sufficiently sensitive to measure the effects of pregnancy, labor, and narcotics on gastric emptying. There was no difference in the rate of gastric emptying between pregnant and nonpregnant females. Labor appeared to cause a significant delay in gastric emptying; the mean +/- SEM time taken for the gastric volume to decrease to 50% (T0.5) was 7.2 +/- 0.6 min during pregnancy and 13.0 +/- 1.9 min in the immediate postpartum period. However, the principal factor associated with the delay in gastric emptying in the group studied within 60 min of delivery was probably the use of meperidine and promethazine, because there was a significant difference (P less than 0.05) between subjects who received meperidine and promethazine during labor and those in another group who had received either no analgesia or extradural analgesia, the T0.5 values for the two groups being 18.2 +/- 4.0 and 10.3 +/- 1.4 min, respectively.
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A comparative review of important classic and Bayesian approaches to fixed-effects and random-effects meta-analysis of binormal ROC curves and areas underneath them is presented. The ROC analyses results of seven evaluation studies concerning the dexamethasone suppression test provide the basis for a worked example. Particular attention is given to fully Bayesian inference, a novelty in the ROC context, based on Gibbs samples from posterior distributions of hierarchical model parameters and related quantities. Fully Bayesian meta-analysis may properly account for the uncertainty associated with the model parameters, possibly incorporating prior knowledge and beliefs, and allows clinically intuitive predictions of unobserved study effects via calculation of posterior predictive densities. The effects of various different prior specifications (six noninformative as well as one informative) on the posterior estimates are investigated (sensitivity-analysis). Recommendations and suggestions for further research are made. Computer code for the more advanced methods may either be downloaded via the Internet or be found elsewhere.