ObjectiveTo evaluate the association between tumor necrosis factor alpha (TNF-α) gene -308G/A polymorphism and the risk of endometriosis (EM). MethodsDatabases including PubMed, EMbase, CBM, CNKI, VIP, and WanFang Data were searched to collect case-control studies about the association between TNF-α gene -308G/A polymorphism and the risk of EM from inception to October 2014. Two reviewers independently screened literature, extracted data, and assessed the risk of bias of included studies. Then Meta-analysis was performed by using Stata 12.0 software. ResultsA total of seven case-control studies were included, which involved 687 patients and 877 controls. The results of meta-analysis showed that, AA genotype carriers presented 2.06-fold (OR=2.06, 95%CI 1.10 to 3.83, P=0.02) and 1.94-fold (OR=1.94, 95%CI 1.18 to 3.18, P<0.01) higher risk of EM than GG genotype carriers and AG+GG genotype carriers, respectively; but sensitivity analysis showed that the robustness of these results was unstable. No statistical significance was found in the allele model, co-dominant model, and dominant model (A vs. G: OR=1.37, 95%CI 0.87 to 2.17, P=0.18; AG vs. GG: OR=1.09, 95%CI 0.77 to 1.53, P=0.63; AA+AG vs. GG: OR=1.29, 95%CI 0.95 to 1.77, P=0.11). While excluding studies that controls were not in HWE, no significant association was observed in these five genetic models; and no significant association was found in the results of subgroup analysis by ethnicity. ConclusionThe AA genotype of TNF-α gene -308G/A polymorphism might contribute to the risk of EM, but the association between other genotypes and EM susceptibility is unclear. In addition, due to the limited quantity and quality of included studies, more high quality studies are needed to verify the above conclusion.
ObjectiveTo evaluate the relationship between tumor necrosis factor-α (TNF-α) gene promoter-308 G/A polymorphism and ankylosing spondylitis (AS) in Chinese population by meta-analysis. MethodsThe casecontrol studies about the correlation between TNF-α gene polymorphism and AS in Chinese population were retrieved from PubMed, EMbase, CNKI, CBM, WanFang Data and VIP database by two researchers. The retrieval time was from their establishment to December, 2015. After the paper screening, data extraction, and assessment of bias risk, the metaanalysis was conducted by Stata 12.0 software. ResultsA total of 11 case-control studies involving 1 154 AS patients and 1 458 controls were included. The results of meta-analysis showed that, for Chinese population, there was no significant association between TNF-α-308 G/A polymorphism and AS susceptibility (A vs. G: OR=0.96, 95% CI 0.63 to 1.47, P=0.86; AA vs. AG: OR=0.97, 95% CI 0.51 to 1.84, P=0.93; AA vs. GG: OR=0.92, 95% CI 0.32 to 2.61, P=0.87; AA+AG vs. GG; OR=1.04, 95% CI 0.60 to 1.80, P=0.89; AA vs. AG+GG: OR=1.03, 95% CI 0.58 to 1.82, P=0.92). ConclusionTo date, it has not found the relationship between TNF-α gene promoter-308 G/A polymorphism and AS in Chinese population. For the quantity and quality limitation of the included studies, the conclusion has to be verified by more large-scale highquality studies.
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.