Odds ratio meta-analysis

One meta-analysis examined the safety and efficacy of LMWH and heparinoids in 11 randomized trials of 3048 patients with acute ischemic stroke. It reported a reduction in the incidence of deep venous thrombosis (DVT) (odds ratio (OR) 0.27,... 

Ioannidis et al. recently showed that after initial reports of associations between polymorphic variants and disease, subsequent studies had lower odds ratios, which were often insignificant, even when meta-analysis... 

Usually, the main purpose of meta-analysis is quantitative. The goal is to develop better overall estimates of the degree of benefit achieved by specific exposure and dosing techniques, based on the combining (pooling) of estimates found in the existing studies of the interventions. This type of meta-analysis is sometimes called a pooled analysis (Gerbarg and Horwitz, 1988) because the analysts pool the observations of many studies and then calculate parameters such as risk ratios or odds ratios from the pooled data. 

Each trial that is to be included in the meta-analysis will provide a measure of treatment effect (difference). For continuous data this could be the mean response on the active treatment minus the mean response in the placebo arm. Alternatively, for binary data the treatment effect could be captured by the difference in the cure rates, for example, or by the odds ratio. For survival data, the hazard ratio would often be the measure of treatment difference, but equally well it could be the difference in the two-year survival rates. 

Benzodiazepines (BZDs) are commonly prescribed in the psychiatric practice to treat anxiety, insomnia, and unpleasant side effects associated with other psychotropic agents. While early case-control studies found that maternal BZD exposure increased the risk of cleft lip and cleft palate, a recent meta-analysis (Dolovich et ah, 1998) examining pooled data from cohort studies published between 1966 and 1998 found no association between antenatal BZD exposure and oral cleft or other major malformations. However, when examining case-control studies published during this period, the authors did find a small, but significant, odds ratio of... 

More innovative methods for examining relationships between individual LOE for the SQT include quantitative estimation of probability derived from odds ratio (Smith et al., 2002) and meta-analysis resulting in pooled, empirically derived P-values (Bailer et al., 2002). Comparison of odds ratio and meta-analysis with PCA for clustering sites into groups of similar impact (Reynoldson et al., 2002a) revealed similarities and differences. The differences between the three methods (PCA, odds ratio and meta-analysis) were ascribed to three factors, which almost certainly apply to all integrations the variables selected the manner in which information is combined within a LOE and, the statistical methodology employed. 

The efficacy of chronic therapy with oral GPIIb/llla inhibitors has been assessed in five major randomized placebo-controlled trials (EXCITE, OPUS, SYMPHONY SYMPHONY II, and BRAVO) (63,64). These agents were associated with a statistically significant increase in mortality in three out of the five trials. A meta-analysis of these trials (n = 45,523) demonstrated a significant increase in mortality (2.8% vs. 2.1% for placebo, odds ratio 1.35, 95% confidence interval 1.15-1.61), mostly... 

DTI meta-analysis. Abbreviations DTI, direct thrombin inhibition MI, myocardial infarction OR, odds ratio PCI, percutaneous coronary intervention UFH, unfractionated heparin. 

Many studies published during the last few decades have suggested that hyperhomocysteinemia is a risk factor for coronary artery disease (CAD), stroke, and thromboembolic disease. The Homocysteine Studies Collaboration metaanalysis of 30 studies concluded that elevated tHcy is a moderate risk factor for ischemic heart disease a level 3 xmol/L lower reduces the risk with an odds ratio of 0.89 (95% Cl = 0.83-0.96). The same was true for homocysteine as a risk factor for stroke (odds ratio = 0.81 95%5CI = 0.69-0.95) (6). A meta-analysis of 40 studies of the MTHFR 677 C > T polymorphism demonstrated a mildly increased risk of coronary heart disease with an odds ratio of 1. 16 (95% Cl = 1.05-1.28) (25). 

Although the majority of randomized studies revealed only insignificant trends toward benefit in the general population, a meta-analysis of nine such studies performed from 1965 to 1987 (two were double-blinded and seven were open) revealed a significant mortality benefit with an odds ratio (OR) of 0.72 [95% confidence interval (Cl) = 0.57-0.90] (47). In the four most recent trials in the general population to date (48-50), only one presented a significant mortality benefit in the GIK infusion group (51). 

In a review of five randomized controlled trials of prevention of relapse in 770 patients with bipolar affective disorder, lithium has been compared with placebo (98). Lithium was more effective than placebo in preventing all relapses and manic relapses, but the effect on depressive relapses was not as impressive and was termed equivocal by the authors. This is not particularly new information, although several of the studies that were included in this meta-analysis were more recent and the analysis was presented as odds ratios rather than episode frequency. 

Fig. 15.3. Meta-analysis of population-based studies showing odds ratios for risk of recurrent stroke at one month according to pathological subtype (Lovett et al. 2004a). Cl, confidence interval p (het), p value for heterogeneity between studies p (sig), p value overall significance of the meta-analysis of comparisons between studies ...

In practice, the analysis involves calculating an odds ratio for each trial included in the meta-... 

In a meta-analysis of 10 studies of the use of amiodarone in patients with heart failure, the overall odds ratio for mortality with amiodarone compared with placebo was 0.79 (95 % Cl = 0.68, 0.92). The corresponding odds ratio for adverse effects was 2.29 (1.97,2.66) (36). The benefit to risk ratio of the use of amiodarone in these patients is not yet clear. The dosage of amiodarone in these studies varied from 50 to 400 mg/day, with an average of around 250 mg/day. 

In a meta-analysis of 42 nicotine chewing gum studies and nine patch studies, comprising 17 000 subjects, the odds ratios of long-term success were 1.61 for gum and 2.07 for patch compared with placebo (1). However, effective use of nicotine gum requires careful instructions. Transdermal uptake of nicotine from patches is about 1 mg/hour (2). Large multicenter studies using 16-hour... 

Since the two meta-analyses in 1995, five prospective, randomized, controlled trials of low-dose corticosteroids in vasopressor-dependent septic shock patients (n = 505) have been published. " These smdies used moderate physiologic doses (200 to 300 mg/day) of hydrocortisone. A meta-analysis of these studies showed that steroid therapy was associated with an overall improvement in survival rate (odds ratio [OR] 1.52, 95% confidence interval [Cl] 1.03-2.27 p =. 036) and shock reversal (OR 4.79, 95% Cl 2.07-11.11 p =. 001). These effects were beneficial in both responders and nonresponders to corticotrophin stimulation testing (p =. 63 and p =. 75, respectively). These smdies also showed that low-dose corticosteroid administration improves hemodynamics and reduces the duration of vasopressor support. " All these studies differ from earlier smdies in that steroids were admimstered later in septic shock (23 hours versus less than 2 hours p =. 02). In these studies, steroids were administered longer (6 days versus 1 day p =. 004), doses were tapered, lower doses were used (hydrocortisone eqmvalents 1209 mg versus 23,975 mg p =. 01), aU patients received high doses of catecholamine vasopressors, and control groups had higher mortality rates (mean 57% versus 34% p =. 03). Since only one of the five studies showed a mortality benefit of low-dose steroids in septic shock, further research is required to confirm this finding. ... 

A meta-analysis of 16 clinical studies showed a benefit of intensive blood glucose control in patients with type 1 diabetes as evidenced by a reduction in the frequency, severity, and a delay in the development or progression of diabetic comphcations including nephropathy. The Epidemiology of Diabetes Interventions and Complications study, which observed the DCCT subjects for an additional 4 years while they were receiving care from primary physicians, showed a continued benefit of IIT on the risk of nephropathy as defined by the development of microalbuminuria (53% odds ratio reduction in microalbuminuria). ... 

In the search for agents to increase bone formation through bone morphogenetic proteins, 3-hydroxymethyl-4-glutaryl CoA reductase inhibitors (statins) were discovered to increase bone density in animal models. Interest in the potential skeletal benefits of statins was heightened by the discovery that bisphosphonates may also affect cholesterol biosynthesis, but at a different step than statins. Although observational studies have linked statin use with decreased fracture risk, a large case-control study did not demonstrate reduction in fracture risk for statin-treated patients. A meta-analysis casts doubt on a protective effect of statins (odds ratio for hip fracture, 0.87 95% Cl 0.48 to 1.58). 02... 

---