PubMed · 14726254
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P Mason. 2004. Update on statins.. https://doi.org/10.1016/j.iccn.2003.10.006
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In many ways, adjustment for publication bias in meta-analysis parallels adjustment for ascertainment bias in genetic studies. We investigate a previously published simulation-based method for dealing with complex ascertainment bias and show that it can be modified for use in meta-analysis when publication bias is suspected. The method involves simulating sets of pseudo-data under the assumed model using guesses for the unknown parameters. The pseudo-data are subjected to the same selection criteria as are believed to have operated on the original data. A conditional likelihood is then used to estimate the adjusted values of the unknown parameters. This method is used to re-analyse a published meta-analysis of the effect of the MTHFR gene on homocysteine levels. Simulation studies show that the pseudo-data method is unbiased; they give an indication of the number of pseudo-data values required and suggest that a two-stage adjustment produces less variable estimates. This method can be thought of as an example of the selection model approach to publication bias correction. As the selection mechanism must be assumed, it is important to investigate the sensitivity of any conclusions to this assumption.
Low density lipoproteins (LDL) do not show in humans a normal distribution and comprise two different main fractions: large, buoyant (phenotype pattern A) and small, dense (phenotype pattern B) particles, that differ not only in size and density but also in physicochemical composition, metabolic behaviour and atherogenicity. The prevalence of small, dense LDL changes with age (30-35% in adult men, 5-10% in men <20 years and in pre-menopausal women, 15-25% in postmenopausal women) and is genetically influenced, with a heritability ranging from 35% to 45%. Small, dense LDL correlate negatively with plasma HDL levels and positively with plasma triglyceride levels and are associated with the metabolic syndrome and with increased risk for cardiovascular disease and diabetes mellitus. LDL size seems also to be an important predictor of cardiovascular events and progression of coronary artery disease and the predominance of small dense LDL has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III. In addition, patients with acute myocardial infarction show an early reduction of LDL size, which persists during hospitalization and seems to precede all other plasma lipoprotein modifications. However, it is still on debate whether to measure the LDL size routinely and in which categories of patients. Since the therapeutic modulation of small, dense LDL particles is of great benefit in reducing the atherosclerotic risk, the LDL size measurement should be extended to patients at high risk of coronary artery disease as much as possible.
This paper reviews the current status of cloning and stem cell research and its application to treating various diseases, particularly cardiovascular disease. Recently new techniques have been developed to isolate embryonic stem cells from preimplantation embryos. These cells are undifferentiated and are therefore able to develop into the cells of whichever organ it is in contact with. These cells would be especially beneficial for the treatment of ischemia and various other cardiovascular diseases. There are a variety of various issues that need to be discussed before this technology can be applied safely, including government regulations to ensure the clinical safety and effectiveness of the procedures, as well as the prevention of improper handling or the use of contaminated tissues.