Inverse Variance (inverse + variance)

Distribution by Scientific Domains

Selected Abstracts

Effects of beverage alcohol price and tax levels on drinking: a meta-analysis of 1003 estimates from 112 studies

ADDICTION, Issue 2 2009
Alexander C. Wagenaar
ABSTRACT Aims We conducted a systematic review of studies examining relationships between measures of beverage alcohol tax or price levels and alcohol sales or self-reported drinking. A total of 112 studies of alcohol tax or price effects were found, containing1003 estimates of the tax/price,consumption relationship. Design Studies included analyses of alternative outcome measures, varying subgroups of the population, several statistical models, and using different units of analysis. Multiple estimates were coded from each study, along with numerous study characteristics. Using reported estimates, standard errors, t -ratios, sample sizes and other statistics, we calculated the partial correlation for the relationship between alcohol price or tax and sales or drinking measures for each major model or subgroup reported within each study. Random-effects models were used to combine studies for inverse variance weighted overall estimates of the magnitude and significance of the relationship between alcohol tax/price and drinking. Findings Simple means of reported elasticities are ,0.46 for beer, ,0.69 for wine and ,0.80 for spirits. Meta-analytical results document the highly significant relationships (P < 0.001) between alcohol tax or price measures and indices of sales or consumption of alcohol (aggregate-level r = ,0.17 for beer, ,0.30 for wine, ,0.29 for spirits and ,0.44 for total alcohol). Price/tax also affects heavy drinking significantly (mean reported elasticity = ,0.28, individual-level r = ,0.01, P < 0.01), but the magnitude of effect is smaller than effects on overall drinking. Conclusions A large literature establishes that beverage alcohol prices and taxes are related inversely to drinking. Effects are large compared to other prevention policies and programs. Public policies that raise prices of alcohol are an effective means to reduce drinking. [source]

Antibacterial efficacy of calcium hydroxide intracanal dressing: a systematic review and meta-analysis

C. Sathorn
Abstract Aim, To determine to what extent does calcium hydroxide intracanal medication eliminate bacteria from human root canals, compared with the same canals before medication, as measured by the number of positive cultures, in patients undergoing root canal treatment for apical periodontitis (teeth with an infected root canal system). Methodology, CENTRAL, MEDLINE and EMBASE databases were searched. Reference lists from identified articles were scanned. A forward search was undertaken on the authors of the identified articles. Papers that had cited these articles were also identified through the Science Citation Index to identify potentially relevant subsequent primary research. Review methods, The included studies were pre-/post-test clinical trials comparing the number of positive bacterial cultures from treated canals. Data in those studies were independently extracted. Risk differences of included studies were combined using the generic inverse variance and random effect method. Results, Eight studies were identified and included in the review, covering 257 cases. Sample size varied from 18 to 60 cases; six studies demonstrated a statistically significant difference between pre- and post-medicated canals, whilst two did not. There was considerable heterogeneity among studies. Pooled risk difference was ,21%; 95% CI: ,47% to 6%. The difference between pre- and post-medication was not statistically significant (P = 0.12). Conclusions, Calcium hydroxide has limited effectiveness in eliminating bacteria from human root canal when assessed by culture techniques. [source]

Accuracy of Ottawa Ankle Rules to Exclude Fractures of the Ankle and Midfoot in Children: A Meta-analysis

Shawn Dowling MD
Abstract Objectives:, The objectives were to conduct a systematic review to determine the diagnostic accuracy of the Ottawa Ankle Rules (OAR) to exclude ankle and midfoot fractures in children and the extent to which x-ray use could be reduced without missing significant fractures. Methods:, The authors conducted comprehensive searches of electronic databases and gray literature sources. Independent reviewers applied standard inclusion and exclusion criteria. The criterion standard diagnostic test was an ankle and/or foot x-ray or proxy measure to ensure no missed fractures. Standard 2 2 tables were constructed. Sensitivities and specificities were pooled using an approximation of the inverse variance; 95% confidence intervals (95% CIs) were calculated using the exact method. Likelihood ratios (LR ) and diagnostic odds ratios were combined under DerSimonian and Laird random effects model. Results:, A pooled analysis of 12 studies (N = 3,130) identified 671 fractures (prevalence = 21.4%). Ten studies reported Salter-Harris Type I (SH-I) fractures. The pooled sensitivity was 98.5% (95% CI = 97.3 to 99.2), suggesting that the OAR can be used to rule out a fracture. Four of 10 missed fractures were characterized: 1 SH-I, 1 SH-IV, and 2 "insignificant fractures" (either SH-I or avulsion fractures <3 mm). The pooled estimate for rate of x-ray reduction was 24.8% (95% CI = 23.3% to 26.3%; range = 5% to 44%). Conclusions:, The OAR appear to be a reliable tool to exclude fractures in children greater than 5 years of age presenting with ankle and midfoot injuries. Employing the OAR would significantly decrease x-ray use with a low likelihood of missing a fracture. [source]

Statistical evaluation of time-dependent metabolite concentrations: estimation of post-mortem intervals based on in situ1H-MRS of the brain

Eva Scheurer
Abstract Knowledge of the time interval from death (post-mortem interval, PMI) has an enormous legal, criminological and psychological impact. Aiming to find an objective method for the determination of PMIs in forensic medicine, 1H-MR spectroscopy (1H-MRS) was used in a sheep head model to follow changes in brain metabolite concentrations after death. Following the characterization of newly observed metabolites (Ith et al., Magn. Reson. Med. 2002; 5: 915,920), the full set of acquired spectra was analyzed statistically to provide a quantitative estimation of PMIs with their respective confidence limits. In a first step, analytical mathematical functions are proposed to describe the time courses of 10 metabolites in the decomposing brain up to 3 weeks post-mortem. Subsequently, the inverted functions are used to predict PMIs based on the measured metabolite concentrations. Individual PMIs calculated from five different metabolites are then pooled, being weighted by their inverse variances. The predicted PMIs from all individual examinations in the sheep model are compared with known true times. In addition, four human cases with forensically estimated PMIs are compared with predictions based on single in situ MRS measurements. Interpretation of the individual sheep examinations gave a good correlation up to 250,h post-mortem, demonstrating that the predicted PMIs are consistent with the data used to generate the model. Comparison of the estimated PMIs with the forensically determined PMIs in the four human cases shows an adequate correlation. Current PMI estimations based on forensic methods typically suffer from uncertainties in the order of days to weeks without mathematically defined confidence information. In turn, a single 1H-MRS measurement of brain tissue in situ results in PMIs with defined and favorable confidence intervals in the range of hours, thus offering a quantitative and objective method for the determination of PMIs. Copyright 2004 John Wiley & Sons, Ltd. [source]