Trial registration and adherence to reporting guidelines in cardiovascular journals.

OBJECTIVE: This study investigated the policies of cardiac and cardiovascular system journals concerning clinical trial registration and guideline adoption to understand how frequently journals use these mechanisms to improve transparency, trial reporting and overall study quality. METHODS: We selected the top 20 (by impact factor) journals cited in the subcategory 'Cardiac and Cardiovascular Systems' of the Expanded Science Citation Index of the 2014 Journal Citation Reports to extract journal policies concerning the 17 guidelines we identified. In addition, trial and systematic review registration adherence statements were extracted. 300 randomised controlled trials published in 2016 in the top 20 journals were searched for clinical trial registry numbers and CONSORT diagrams. RESULTS: Of the 19 cardiac and cardiovascular system journals included in our analysis, eight journals (42%) did not require or recommend trial or review registration. Seven (37%) did not recommend or require a single guideline within their instructions to authors. Consolidated Standards for Reporting Trials guidelines (10/19, 53%) were recommended or required most often. Of the trials surveyed, 122/285 (42.8%) published a CONSORT diagram in their manuscript, while 236/292 (80.8%) published a trial registry number. DISCUSSION: Cardiac and cardiovascular system journals infrequently require, recommend or enforce the use of reporting guidelines. Furthermore, too few require or enforce the use of clinical trial registration. Cardiology journal editors should consider guideline adoption due to their potential to limit bias and increase transparency.

The association of the mitochondrial DNA OriB variant (16184-16193 polycytosine tract) with type 2 diabetes in Europid populations.

AIMS/HYPOTHESIS: The association between the mitochondrial DNA 16181-16193 polycytosine variant (known as the OriB variant as it maps to the OriB origin of replication) and type 2 diabetes has not been reliably characterised, with studies reporting conflicting results. We report a systematic review of published literature in Europid populations, new data from the Norfolk Diabetes Case-Control Study and a meta-analysis to help quantify this association. METHODS: We performed a systematic review identifying all the studies of the OriB variant and type 2 diabetes in Europid populations published before January 2013. We typed the OriB variant by pyrosequencing and sequencing in the Norfolk Diabetes Case-Control Study, which comprised 5,574 type 2 diabetes cases and 6,950 population-based controls. RESULTS: Overall, the meta-analysis included eight published studies plus the current new results, with a total of 11,794 type 2 diabetes cases and 14,465 controls. In the Norfolk Diabetes Case-Control Study, the OR for type 2 diabetes for the OriB variant was 1.09 (95% CI 0.96, 1.24). In a combined analysis, the relative risk for type 2 diabetes for the OriB variant in Europid populations was 1.10 (95% CI 1.01, 1.20; p = 0.03) CONCLUSIONS/INTERPRETATION: Results from this systematic review and meta-analysis suggest that the mitochondrial DNA OriB variant is modestly associated with an increased risk of type 2 diabetes in Europid populations, with an effect size comparable with that of recently identified variants from genome-wide association studies.

Sources of pre-analytical variations in yield of DNA extracted from blood samples: analysis of 50,000 DNA samples in EPIC.

The European Prospective Investigation into Cancer and nutrition (EPIC) is a long-term, multi-centric prospective study in Europe investigating the relationships between cancer and nutrition. This study has served as a basis for a number of Genome-Wide Association Studies (GWAS) and other types of genetic analyses. Over a period of 5 years, 52,256 EPIC DNA samples have been extracted using an automated DNA extraction platform. Here we have evaluated the pre-analytical factors affecting DNA yield, including anthropometric, epidemiological and technical factors such as center of subject recruitment, age, gender, body-mass index, disease case or control status, tobacco consumption, number of aliquots of buffy coat used for DNA extraction, extraction machine or procedure, DNA quantification method, degree of haemolysis and variations in the timing of sample processing. We show that the largest significant variations in DNA yield were observed with degree of haemolysis and with center of subject recruitment. Age, gender, body-mass index, cancer case or control status and tobacco consumption also significantly impacted DNA yield. Feedback from laboratories which have analyzed DNA with different SNP genotyping technologies demonstrate that the vast majority of samples (approximately 88%) performed adequately in different types of assays. To our knowledge this study is the largest to date to evaluate the sources of pre-analytical variations in DNA extracted from peripheral leucocytes. The results provide a strong evidence-based rationale for standardized recommendations on blood collection and processing protocols for large-scale genetic studies.