Meta-analysis Of Case-control Studies Research Articles

A meta-analysis of genotypes and haplotypes of methylenetetrahydrofolate reductase gene polymorphisms in acute lymphoblastic leukemia

A meta-analysis of case-control studies that investigated the association between the C677T and/or A1298C polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene and acute lymphoblastic leukemia (ALL) was carried out. Pooled odds ratios (OR) of various genetic contrasts of each polymorphism were estimated using random (RE) and fixed effects (FE) models. Pooled ORs for combined genotypes and haplotypes were estimated after adjustment for study effect using a log-linear model and the expectation-maximization algorithm in combination with log-linear modeling, respectively. The recessive model for allele 1298C produced a rather marginal association: RE OR: 0.67; 95% confidence interval (CI): 0.46-0.99 and FE OR: 0.64; 95% CI: 0.49-0.84. In Caucasians, the results of the recessive model for allele 1298C was consisted with a protective effect of ALL development: FE OR: 0.63; 95% CI: 0.46-0.87. In childhood ALL, according to the results of the allele contrast and the recessive model for 677T allele it was conceivable that a protective effect exist: RE OR = 0.74; 95% CI: 0.57-0.96 and RE OR: 0.69; 95% CI: 0.51-0.94, respectively. The combined genotypes produced significant pooled OR for the 677CC/1298CC relative to 677CC/1298AA (OR: 0.54; 95% CI: 0.36-0.80). The haplotype 677C/1298C might be more protective to ALL relative to haplotype 677C/1298A (OR: 0.77; 95% CI: 0.61-0.97). When studies not in Hardy-Weinberg equilibrium (HWE) were corrected to account for departures from HWE, then, the pattern of results remained the same. Overall, there is high heterogeneity between the studies in both polymorphisms. A differential magnitude of effect in large versus small studies and alteration of early extremes effects existed.

Meat Consumption Is a Risk Factor for Colorectal Cancer: Meta-Analysis of Case-Control Studies

Meat has been associated with an increased risk of colorectal cancer in most, but not all, studies. Findings have shown conflicting results and inconclusive with regard to meat consumption in the colorectal cancers. To resolve these inconsistencies, we conducted a meta-analysis of published data on the association between meat and the incidence of colorectal cancer. Meta-analysis method was conducted to estimate the combined odds ratio (OR) between meat consumption and colorectal cancer from case-control studies published between 1989 and 2005. The combined odds ratio (OR) was 1.68 (95% CI; 1.34-2.12) in the 12 published case-control studies. The combined OR varied little by types of meat. Additionally, we evaluated the possible risk factors in meat for colorectal cancer. In conclusion, we found a positive association between meat consumption and colorectal cancer.

Milk Consumption Is a Risk Factor for Prostate Cancer: Meta-Analysis of Case-Control Studies

Prostate cancer has become the most common cancer among men in the United States. Although milk consumption is considered to be a risk factor in some epidemiological studies, the results are inconsistent. A meta-analysis method was conducted to estimate the combined odds ratio (OR) between milk consumption and prostate cancer from case-control studies published between 1984 and 2003 using commercial software (comprehensive meta-analysis). The combined OR was 1.68 (95% confidence interval = 1.34-2.12) in the 11 published case-control studies. The combined OR varied little by study stratification. Additionally, we evaluated the possible risk factors in milk for prostate cancer. In conclusion, we found a positive association between milk consumption and prostate cancer. The underlying mechanisms, including fat, calcium, hormones, and other factors, should be investigated further.

Meta-analysis of the relationship between cagA seropositivity and gastric cancer

Background & Aims : Reports in the literature regarding the relationship of infection with cagA-positive strains of Helicobacter pylori to gastric cancer over and above H. pylori infection alone are conflicting. The aim of this study was to estimate the magnitude of the risk for gastric cancer associated with cagA seropositivity and to identify any sources of heterogeneity between studies. Methods : A meta-analysis of case-control studies with age- and sex-matched controls, which provided raw data on the infection rates with H. pylori and cagA strains of H. pylori as detected by serology or polymerase chain reaction DNA, was performed. Results : A comprehensive literature search identified 16 qualified studies with 2284 cases and 2770 controls. H. pylori and cagA seropositivity significantly increased the risk for gastric cancer by 2.28- and 2.87-fold, respectively. Among H. pylori-infected populations, infection with cagA-positive strains further increased the risk for gastric cancer by 1.64-fold (95% confidence interval [CI], 1.21–2.24) overall and by 2.01-fold (95% CI, 1.21–3.32) for noncardia gastric cancer. Gastric cancer at the cardia is not associated with H. pylori infection or cagA-positive strains of H. pylori. Patient age and site of gastric cancer contributed to the heterogeneity between studies. Conclusions : Infection with cagA-positive strains of H. pylori increases the risk for gastric cancer over the risk associated with H. pylori infection alone. Searching for cagA status over H. pylori infection may confer additional benefit in identifying populations at greater risk for gastric cancer.

Patent Foramen Ovale and Recurrent Stroke

Clinical management of patients with acute stroke and the approach used for secondary prevention depends upon clarification of pathogenesis. Although most strokes are a consequence of cerebrovascular disease, ≈15% to 20% of ischemic (nonhemorrhagic) strokes have been attributed to cardiogenic embolism.1 In practice, determination of the stroke mechanism is fraught with uncertainty, particularly when the possibility of thromboembolism emanating from atherosclerotic lesions in the aorta or cervical arteries is considered. When cardiogenic embolism is suspected, cardiac ultrasound is the principal method used to identify the potential source. The finding of left atrial enlargement has been shown to bear a significant relationship to the risk of stroke in a multivariate analysis of population-based data from the Framingham Heart Study2. The most frequent confounding variable is atrial fibrillation, occurring in >2 million patients in North America and in over half of all patients with cardiogenic embolism. Criteria for selection of patients with acute ischemic stroke for transesophageal echocardiography (TEE) to search for a potential cardiac source of embolism are controversial, particularly because cardiogenic embolism is often an uncertain diagnosis that is inferred merely on the basis of the finding of potential cardiac source. Even after extensive investigation, ≈40% of ischemic stroke patients have no clearly identifiable pathogenesis (cryptogenic stroke).3 In one study, 62% of patients younger than 60 years of age without an obvious source of cerebral infarction and 23% of those with arterial lesions had potential sources of cardiogenic embolism identified by TEE ( P =0.0007 for the difference).4 See p 2625 Among the cardiac anomalies detected by TEE that have been implicated as risk factors for stroke are patent foramen ovale (PFO) and atrial septal aneurysm (ASA).5,6⇓ The foramen ovale, a remnant of the fetal circulation, remains patent through adulthood in ≈1 in 4 …

The effect of day care exposure on the risk of developing type 1 diabetes: a meta-analysis of case-control studies.

Exposure to infections in infancy or childhood may be important in the pathogenesis of type 1 diabetes, but a protective role has also been suggested. We tested the hypothesis that increased early contact with infectious agents, measured by day care exposure, would decrease the risk of type 1 diabetes in childhood. We conducted a systematic review of case-control studies. Meta-analysis was performed to combine results, assess for heterogeneity, and explore variation in study design. Several generally well-designed case-control studies show a statistically significant protective effect of day care on type 1 diabetes. However, meta-analysis revealed too much heterogeneity to accept the overall synthesis results and none of the studies used prerecorded data. Day care does seem to have a protective effect in the subgroup of children who will be diagnosed with type 1 diabetes before the age of 5 years (odds ratio = 0.6, 95% CI 0.5-0.8); however, this result is based on only two studies. Recall bias is one alternate explanation for these data; confirmation using prerecorded data is required. Such data could be prospectively measured in cohort studies of children at risk. We also suggest that information about day care attendance be measured in randomized trials of agents for the prevention of type 1 diabetes, as day care exposure could potentially modify the effect of the preventive agent.

Interatrial septal abnormalities and stroke: a meta-analysis of case-control studies.

To examine the association between patent foramen ovale (PFO) and atrial septal aneurysm (ASA) and stroke. Data from case-control studies that examined the relative frequency of PFO, ASA, or both, in all patients with ischemic stroke, cryptogenic stroke, and known stroke cause as well as control subjects were included. Trials were categorized by age, clinical comparison, and abnormality. Combined OR were calculated using fixed effect (FE) and random effect (RE) methods. Comparing patients with ischemic stroke with control subjects using RE, OR for all ages was 1.83 (95% CI, 1.25 to 2.66) for PFO (15 studies), 2.35 (95% CI, 1.46 to 3.77) for ASA (nine studies), and 4.96 (95% CI, 2.37 to 10.39) for PFO plus ASA (four studies). Homogeneous results were found within the group younger than age 55: using FE, OR was 3.10 (95% CI, 2.29 to 4.21) for PFO, 6.14 (95% CI, 2.47 to 15.22) for ASA, and 15.59 (95% CI, 2.83 to 85.87) for PFO plus ASA. For patients older than age 55, using FE, OR was 1.27 (95% CI, 0.80 to 2.01) for PFO, 3.43 (95% CI, 1.89 to 6.22) for ASA, and 5.09 (95% CI, 1.25 to 20.74) for PFO plus ASA. Comparing cryptogenic stroke with known stroke cause, heterogeneous results were derived from total group examination using RE: OR was 3.16 (95% CI, 2.30 to 4.35) for PFO (22 studies), 3.65 (95% CI, 1.34 to 9.97) for ASA (five studies), and 23.26 (95% CI, 5.24 to 103.20) for PFO plus ASA (two studies). In patients younger than age 55, using FE the OR was 6.00 (95% CI, 3.72 to 9.68) for PFO; only one study examined ASA or PFO plus ASA. In patients aged 55 years or older, three studies produced heterogeneous results for PFO: using RE, OR was 2.26 (95% CI, 0.96 to 5.31); no data were available on ASA prevalence. PFO and ASA are significantly associated with ischemic stroke in patients younger than 55 years. Further studies are needed to establish whether an association exists between PFO and ischemic stroke in those older than 55.

The sparteine/debrisoquine (CYP2D6) oxidation polymorphism and the risk of Parkinson??s disease

The association between the sparteine/debrisoquine (CYP2D6) oxidation polymorphism and the risk of Parkinson's disease was examined in a meta-analysis of case-control studies. The odds ratio was calculated for the risk of Parkinson's disease among poor metabolisers compared with extensive metabolisers. Twenty-one studies were identified of which six were excluded because they were not reported as full papers (n = 3), used incomplete genotype analysis (n = 2) or used Parkinson patients as both control individuals and cases (n = 1). The overall odds ratio was 1.48 (95% confidence interval 1.10-1.99). The odds ratio was 1.05 (95% confidence interval 0.63-1.77) in studies discriminating extensive and poor metabolisers by phenotyping (n = 8) and 1.67 (95% confidence interval 1.11-2.50) in studies using genotyping (n = 7). This difference was caused by a single large study using genotyping. We conclude that there is no convincing evidence of an association between the debrisoquine/sparteine polymorphism and Parkinson's disease. However, it could prove worthwhile to perform another large study using genotyping.

The sparteine/debrisoquine (CYP2D6) oxidation polymorphism and the risk of lung cancer: a meta-analysis.

To examine the association between the sparteine/debrisoquine (CYP2D6) oxidation polymorphism and the risk of lung cancer. Meta-analysis of case-control studies using a random effects model. The "Main outcome measure" was the odds ratio for the risk of lung cancer, using extensive metabolisers as the reference group. Thirteen studies were identified. The studies were too heterogeneous to be pooled the size of the odds ratio increased with the sample size. When the analysis was restricted to the largest studies, there was no difference in risk between poor and extensive metabolisers (odds ratio 0.95, 95% confidence interval 0.68-1.33). No association was found between the CYP2D6 oxidation polymorphism and lung cancer risk when sample size bias was taken into account.

IUD use and the risk of ectopic pregnancy: A meta-analysis of case-control studies

Because of inconsistent findings among case-control studies on the relationship between IUD use and the risk of ectopic pregnancy, a meta-analysis of published literature was conducted. From 1977 through 1994, 19 publications regarding 16 studies of ectopic pregnancy and IUD use were found by MEDLINE and manual search. The odds ratios (ORs) of ectopic pregnancy with current and past IUD use in each study were pooled. A quality score system was developed to assess each study. Funnel plot was used to assess potential publication biases. For current IUD use, when cases were compared to pregnant controls, there was an increased risk of ectopic pregnancy (pooled OR: 10.63, 95% confidence interval (CI): 7.66–14.74); when cases were compared to non-pregnant controls, there was no risk of ectopic pregnancy (pooled OR: 1.06, 95% CI: 0.91–1.24). Past IUD use could mildly increase the risk of ectopic pregnancy (pooled OR: 1.40, 95% CI: 1.23–1.59). Selecting pregnant or non-pregnant women as controls, however, did not affect the OR estimates of past IUD use. Current IUD use does not increase the risk of ectopic pregnancy. However, a pregnancy with an IUD in situ is more often an ectopic one than a pregnancy with no IUD. Past IUD use could mildly elevate the risk of ectopic pregnancy.