Literature Search Strategy
Use the following keywords: “Homeobox Protein Nkx 2.5”, “Nkx-2.5, Homeobox Protein”, “NK2 Homeobox 5 Protein”, “Homeobox Transcription Factor Csx-Nkx2-5”, “Homeobox Transcription Factor Csx Nkx2 5”, “Homeobox Protein Csx-Nkx2.5”, “Csx-Nkx2.5, Homeobox Protein”, “Homeobox Protein Csx Nkx2.5”, “Cardiac-Specific Homeobox Protein”, “Cardiac Specific Homeobox Protein”, “Homeobox Protein, Cardiac-Specific”, “Transcription Factor Nkx-2.5”, “Nkx-2.5, Transcription Factor”, “Transcription Factor Nkx 2.5”, “Nucleotide Polymorphism, Single”, “Nucleotide Polymorphisms, Single”, “Polymorphisms, Single Nucleotide”, “Single Nucleotide Polymorphisms”, “SNPs”, “Single Nucleotide Polymorphism” to carry out an unlimited search of electronic databases of PubMed, MEDLINE, EMBASE, Web of science, Coherane, China National Knowledge Infrastructure (CNKI), Wanfang DATA, VIP database. The initial search was conducted in Sep 1, 2021, identified relevant articles published as of Aug 31, 2021. We conducted the meta-analysis and report the results based on the preferred reporting items stated by System Review and Meta-Analysis (PRISMA).
The inclusion criteria for this study were formulated before the literature search. Eligible studies met the following conditions: (1) Articles that have been published electronically; (2) Case-control studies of unrelated CHD patients and healthy controls; (3) Evaluation of the correlation between NKX2.5 606G> C polymorphism (rs3729753) and the risk of CHD ; (4) Provided sufficient genotype data to calculate odds ratios (ORs), corresponding 95% confidence intervals (CIs) and could be able to establish various genetic models (5) All texts are available in English or Chinese; (6) Histological or pathological confirmation Of non-syndromic CHD; All clinical types, such as atrial septal defect (ASD) and ventricular septal defect (VSD), were included in this meta-analysis. Pedigree studies, case reports, case series, reviews, editorials, the meta-analysis, animal studies, expert opinions, and studies that consider CHD as part of any known genetic disease or multiple congenital abnormalities syndrome were excluded.
Data Extraction
The two reviewers independently extracted the following information from the included studies: first author, year of publication, country, type of study design, types of CHD, genotype and gene frequency in patients with CHD and control group, and whether the NKX2.5 gene polymorphism was in accordance with Hardy-Weinberg equilibrium (HWE) in the control group. Using the classic assessment tool, the Newcastle-Ottawa Quality Assessment Scale (NOS), to evaluate the quality of non-randomized studies from the perspectives of selection, comparability, exposure, and evaluate the effectiveness of all case-control studies. Two reviewers (HC and XW) independently performed data extraction and quality evaluation. When necessary, the reviewer wrote to the author to obtain additional information or original data.
Statistical Analysis
All data were analyzed by Stata software version 16.0(Stata Corp LP, TX, USA). If the P-value <0.05, the difference was considered statistically significant. Chi-square test was used to calculate the P value of the control group HWE. The association between SNP 606G> C and susceptibility to CHD was estimated by combined odds ratios (ORs) and 95% confidence intervals (CIs) under different genetic models. Cochran ’s Q statistical test was used to assess heterogeneity between studies. If the probability value (P-value) was less than 0.1 or I2 is greater than 50%, the random effect model was used because of the significant heterogeneity; otherwise, the fixed-effect model was applied. Then the subgroup analysis based on the type of CHD was performed. Sensitivity analysis was performed to assess the impact of each individual study on the overall estimate. Begg and Egger's tests were used to assess potential publication bias.