Dose-response meta-analysis, as a subset of meta-analysis, plays an important role in dealing with the relationship between exposure level and risk of diseases. Traditional models limited in linear regression between the independent variables and the dependent variable. With the development of methodology and functional model, Nonlinear regression method was applied to dose-response meta-analysis, such as restricted cubic spline regression, quadratic B-spline regression. However, in these methods, the term and order of the independent variables have been assigned that may not suit for any trend distribution and it may lead to over fitting. Flexible fraction polynomial regression is a good method to solve this problem, which modelling a flexible fraction polynomial and choosing the best fitting model by using the likelihood-ratio test for a more accurate evaluation. In this article, we will discuss how to conduct a dose-response meta-analysis by flexible fraction polynomial.
when we conducted a meta-analysis, it is often an annoying thing to deal with the data of discrete exposure and multiple outcomes. Conventional "high VS low" approach abandoned the information of middle category, and led to the loss of statistical power. In this paper, we introduced a method and software to combine the groups of discrete exposure and multiple outcomes in the meta-analysis of epidemiological studies. Firstly, we introduced the transforming and combination theory and method, and then, we conducted the combination using EXCEL macro software. The result was consistent with the results of the original data in the combination of discrete exposure and multiple outcome data. Therefore, in the case of the original research data cannot be acquired, EXCEL macro software can be a good solution.
The key for performing meta-analysis using WinBUGS software is to construct a model of Bayesian statistics. The hand-written code model and Doodle model are two major methods for constructing it. The approach of hand-written code is flexible and convenient, but the language programming is fallibility. The Doodle is complicated, but it is benefit to understand the structure of hand-written code model and prevent error. This article briefly describes how to construct the Doodle model for binary and continuous data of head to head meta-analysis, indirect comparison and network meta-analysis, and ordinal variables meta-analysis.
ITC (Indirect Treatment Comparison) software and indirect procedure of Stata software are especially used for indirect comparison nowadays, both of which possess the characteristics of friendly concise interface and support for menu operation. ITC software needs the application of other software to yield effect estimation and its confidence interval of direct comparison firstly; while Stata-indirect procedure can complete direct comparison internally and also operate using commands, which simplifies complicated process of indirect comparison. However, both of them only perform "single-pathway" of data transferring and pooling, which is a common deficiency. From the results, their results are of high-degree similarity.
ObjectiveTo explore the effectiveness of thoracoscopic surgery for treating late-presenting congenital diaphragmatic hernias and summarize the experience. MethodsBetween October 2012 and February 2015, 21 children with late-presenting congenital diaphragmatic hernias underwent thoracoscopic surgery. Of the 21 cases, 12 were girls and 9 were boys with a median age of 1 year and 3 months (range, 2 months to 8 years). Eight patients had obvious symptom in the initial stage:shortness of breath and dyspnea; 13 cases were found occasionally through chest radiography. Of 21 cases, 17 had left diaphragmatic hernias and 4 had right diaphragmatic hernias. The emergency surgery was performed in 5 cases because oppressed obviously and selective operation in 16 cases. Hernial sac existed in 5 cases; there were 19 cases of Bochdalek's hernia and 2 cases of Morgagni's hernia. The size of diaphragmatic defect ranged from 3 cm×2 cm to 5 cm×5 cm. ResultsThe operation time was 35-80 minutes (mean, 50 minutes), and intraoperative blood loss was 3-5 mL (mean, 3.8 mL). Primary healing of incision was obtained. Postoperative abdominal distension and pneumothorax occurred in 12 and 2 cases respectively. The follow-up time was 1-3 years (mean, 20 months). All the cases had a good recovery and satisfactory appearance of the thoracic incision. The symptoms and signs of shortness of breath and dyspnea disappeared. There was no recurrence and chest infection. ConclusionUnder the conditions of mastering operative indications strictly, thoracoscopic repair for late-presenting congenital diaphragmatic hernia is safe and feasible. It can facilitate the procedure and decrease the recurrence rate relying on intraoperative application of hernia repair needle, knot pusher-assistant, and reasonable processing defect periphery.
Does-response meta-analysis, which has being developed for more than 30 years, is a type of regression function and can be both linear and non-linear model. It plays an important role in investigating the relationship between dependent and independent variable. With its special advantages, dose-response meta-analysis has been widely used in evidence-based practice and decision. Currently there are several models can be used to perform dose-response metaanalysis with various advantages and disadvantages. It is vital to choose best model to perform dose-response metaanalysis in evidence-based practice. In this paper, we briefly introduce and summarize the methodology of dose-response meta-analysis.
Restricted cubic spline function is an ideal model in trend approximation, which is widely used in doseresponse meta-analysis. The spline function, based on parameter technique, is a smoothly joined piecewise polynomial of each knot, with a cubic polynomial in each sub-interval of the slope which fits well in the non-linear trend by changing the number and (or) the sites of the knots. We have introduced the methodology of linear and non-linear slope model in dose-response meta-analysis in the previous article, and in this one, we will give a more detailed discussion on restricted cubic spline function mainly in the following aspects: model building, parameters pooling and knots selecting.
Dose-response meta-analysis, an important tool in investigating the relationship between a certain exposure and risk of disease, has been increasingly applied. Traditionally, the dose-response meta-analysis was only modelled as linearity. However, since the proposal of more powerful function models, which contains both linear, quadratic, cubic or more higher order term within the regression model, the non-linearity model of dose-response relationship is also available. The packages suit for R are available now. In this article, we introduced how to conduct a dose-response meta-analysis using dosresmeta and mvmeta packages in R.
When investing the relationship between independent and dependent variables in dose-response meta-analysis, the common method is to fit a regression function. A well-established model should take both linear and non-linear relationship into consideration. Traditional linear dose-response meta-analysis model showed poor applicability since it was based on simple linear function. We introduced a piecewise linear function into dose-response meta-analysis model which overcame this problem. In this paper, we will give a detailed discussion on traditional linear and piecewise linear regression model in dose-response meta-analysis.
Structural equation modeling (SEM) is a frequently used multivariate technique in social, psychology, educational, behavioral science. Meta-analytic structural equation modeling (MASEM) combines the ideas of metaanalysis and structural equation modeling for the purpose of synthesizing correlation or covariance matrices and fitting structural equation models on the pooled correlation or covariance matrix. A two-stage structural equation modeling (TSSEM) approach to conducting MASEM that was based on a fixed-effects model will be introduced. To introduce the operation of metaSEM package for multivariate meta-analyst, we are adopt the fixed-effects model, assumes that the population correlation matrices based on TSSEM, to analyze the instance data.