Diabetes Mellitus and Keratoconus: A Systematic Review and Meta-Analysis.

PURPOSE: Although previous studies have assessed the relationship between diabetes and keratoconus, the findings were controversial and warranted further clarifications. The objective of this study was to investigate the association between diabetes and keratoconus by conducting a systematic review and meta-analysis. METHODS: A comprehensive literature search was performed to identify eligible studies reporting the association of diabetes with keratoconus from their inception to April 2021 through PubMed, Embase, and Web of Science. The quality of included studies was assessed using the Newcastle-Ottawa scale. Combined odds ratios (ORs) and 95% confidence intervals were calculated using a random-effects model. RESULTS: In all, 8 case-control studies and 3 cohort studies reporting the association between diabetes and keratoconus were included in the meta-analysis. Diabetes was not associated with keratoconus in the overall analysis (combined OR = 0.85, 95% confidence interval: 0.66-1.10). The associations were found to be nonsignificant in subgroup analysis when stratified by study quality, design, source, types, and population. No publication bias was detected from either the Egger test (P = 0.46) or Begg test (P = 0.16). Sensitivity analysis revealed that differences between groups were not statistically significant. CONCLUSIONS: This meta-analysis indicates that current literature does not support a significant association between diabetes and keratoconus. Further studies with more definite control for confounders and well-designed cohorts or interventions are warranted.

Utility of GDF-15 as a diagnostic biomarker in gastric cancer: an investigation combining GEO, TCGA and meta-analysis.

It was recently suggested that growth differentiation factor-15 (GDF-15) is associated with gastric cancer (GC) carcinogenesis. However, the diagnostic potential of GDF-15 for GC remains unclear. To address this issue, we obtained RNA sequencing and microarray data from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases, and searched PubMed, Google Scholar and Web of Science for relevant literature. We then used STATA to perform a meta-analysis. In total, reports of 253 GC patients and 112 healthy controls who contributed peripheral blood samples were taken from the four literature sources, while information on 754 GC tumor and 263 gastric normal tissues was drawn from TCGA and seven GEO datasets. The expression level of GDF-15 mRNA was significantly higher in tumor tissues than in normal tissues, with a standard mean difference (SMD) of 0.79% and a 95% confidence interval (95% CI) of 0.63-0.95. Consistently, the GDF-15 protein in blood was significantly increased in GC patients as compared to controls (SMD  = 3.74, 95% CI = 1.81-5.68). In addition, based on information from TCGA and GEO datasets, the expression level of GDF-15 mRNA may be of use for the diagnosis of GC, with a combined sensitivity, specificity and odds ratio of 0.69 (95% CI = 0.58-0.79), 0.90 (95% CI = 0.84-0.93) and 6.32 (95% CI = 4.22-9.49), respectively. The summary receiver operating characteristic curve demonstrated that the area under the curve was 0.90 (95% CI = 0.87-0.93). The results suggest higher levels of GDF-15 may be associated with GC tumorigenesis and may have the potential to be a diagnostic biomarker of GC.