@article {943, title = {Collaborative meta-analysis of individual participant data from observational studies of Lp-PLA2 and cardiovascular diseases.}, journal = {Eur J Cardiovasc Prev Rehabil}, volume = {14}, year = {2007}, month = {2007 Feb}, pages = {3-11}, abstract = {

BACKGROUND: A large number of observational epidemiological studies have reported generally positive associations between circulating mass and activity levels of lipoprotein-associated phospholipase A2 (Lp-PLA2) and the risk of cardiovascular diseases. Few studies have been large enough to provide reliable estimates in different circumstances, such as in different subgroups (e.g., by age group, sex, or smoking status) or at different Lp-PLA2 levels. Moreover, most published studies have related disease risk only to baseline values of Lp-PLA2 markers (which can lead to substantial underestimation of any risk relationships because of within-person variability over time) and have used different approaches to adjustment for possible confounding factors.

OBJECTIVES: By combination of data from individual participants from all relevant observational studies in a systematic {\textquoteright}meta-analysis{\textquoteright}, with correction for regression dilution (using available data on serial measurements of Lp-PLA2), the Lp-PLA2 Studies Collaboration will aim to characterize more precisely than has previously been possible the strength and shape of the age and sex-specific associations of plasma Lp-PLA2 with coronary heart disease (and, where data are sufficient, with other vascular diseases, such as ischaemic stroke). It will also help to determine to what extent such associations are independent of possible confounding factors and to explore potential sources of heterogeneity among studies, such as those related to assay methods and study design. It is anticipated that the present collaboration will serve as a framework to investigate related questions on Lp-PLA2 and cardiovascular outcomes.

METHODS: A central database is being established containing data on circulating Lp-PLA2 values, sex and other potential confounding factors, age at baseline Lp-PLA2 measurement, age at event or at last follow-up, major vascular morbidity and cause-specific mortality. Information about any repeat measurements of Lp-PLA2 and potential confounding factors has been sought to allow adjustment for possible confounding and correction for regression dilution. The analyses will involve age-specific regression models. Synthesis of the available observational studies of Lp-PLA2 will yield information on a total of about 15 000 cardiovascular disease endpoints.

}, keywords = {1-Alkyl-2-acetylglycerophosphocholine Esterase, Cardiovascular Diseases, Humans, Phospholipases A2}, issn = {1741-8267}, doi = {10.1097/01.hjr.0000239464.18509.f1}, author = {Ballantyne, C and Cushman, M and Psaty, B and Furberg, C and Khaw, K T and Sandhu, M and Oldgren, J and Rossi, G P and Maiolino, G and Cesari, M and Lenzini, L and James, S K and Rimm, E and Collins, R and Anderson, J and Koenig, W and Brenner, H and Rothenbacher, D and Berglund, G and Persson, M and Berger, P and Brilakis, E and McConnell, J P and Koenig, W and Sacco, R and Elkind, M and Talmud, P and Rimm, E and Cannon, C P and Packard, C and Barrett-Connor, E and Hofman, A and Kardys, I and Witteman, J C M and Criqui, M and Corsetti, J P and Rainwater, D L and Moss, A J and Robins, S and Bloomfield, H and Collins, D and Packard, C and Wassertheil-Smoller, S and Ridker, P and Ballantyne, C and Cannon, C P and Cushman, M and Danesh, J and Gu, D and Hofman, A and Nelson, J J and Thompson, S and Zalewski, A and Zariffa, N and Di Angelantonio, E and Kaptoge, S and Thompson, A and Thompson, S and Walker, M and Watson, S and Wood, A} } @article {1171, title = {Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables.}, journal = {Stat Med}, volume = {29}, year = {2010}, month = {2010 May 30}, pages = {1298-311}, abstract = {

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

}, keywords = {Bayes Theorem, Biostatistics, C-Reactive Protein, Fibrinogen, Genetic Markers, Humans, Meta-Analysis as Topic, Models, Statistical, Phenotype, Polymorphism, Single Nucleotide}, issn = {1097-0258}, doi = {10.1002/sim.3843}, author = {Burgess, Stephen and Thompson, Simon G and Burgess, S and Thompson, S G and Andrews, G and Samani, N J and Hall, A and Whincup, P and Morris, R and Lawlor, D A and Davey Smith, G and Timpson, N and Ebrahim, S and Ben-Shlomo, Y and Davey Smith, G and Timpson, N and Brown, M and Ricketts, S and Sandhu, M and Reiner, A and Psaty, B and Lange, L and Cushman, M and Hung, J and Thompson, P and Beilby, J and Warrington, N and Palmer, L J and Nordestgaard, B G and Tybjaerg-Hansen, A and Zacho, J and Wu, C and Lowe, G and Tzoulaki, I and Kumari, M and Sandhu, M and Yamamoto, J F and Chiodini, B and Franzosi, M and Hankey, G J and Jamrozik, K and Palmer, L and Rimm, E and Pai, J and Psaty, B and Heckbert, S and Bis, J and Anand, S and Engert, J and Collins, R and Clarke, R and Melander, O and Berglund, G and Ladenvall, P and Johansson, L and Jansson, J-H and Hallmans, G and Hingorani, A and Humphries, S and Rimm, E and Manson, J and Pai, J and Watkins, H and Clarke, R and Hopewell, J and Saleheen, D and Frossard, R and Danesh, J and Sattar, N and Robertson, M and Shepherd, J and Schaefer, E and Hofman, A and Witteman, J C M and Kardys, I and Ben-Shlomo, Y and Davey Smith, G and Timpson, N and de Faire, U and Bennet, A and Sattar, N and Ford, I and Packard, C and Kumari, M and Manson, J and Lawlor, Debbie A and Davey Smith, George and Anand, S and Collins, R and Casas, J P and Danesh, J and Davey Smith, G and Franzosi, M and Hingorani, A and Lawlor, D A and Manson, J and Nordestgaard, B G and Samani, N J and Sandhu, M and Smeeth, L and Wensley, F and Anand, S and Bowden, J and Burgess, S and Casas, J P and Di Angelantonio, E and Engert, J and Gao, P and Shah, T and Smeeth, L and Thompson, S G and Verzilli, C and Walker, M and Whittaker, J and Hingorani, A and Danesh, J} }