A simple method for estimating relative risk using logistic regression

Grupo Latinoamericano de Investigaciones Epidemiológicas, Organización Latinoamericana para el Fomento de la Investigación en Salud, Bucaramanga, Colombia.
BMC Medical Research Methodology (Impact Factor: 2.17). 02/2012; 12:14. DOI: 10.1186/1471-2288-12-14
Source: PubMed

ABSTRACT Odds ratios (OR) significantly overestimate associations between risk factors and common outcomes. The estimation of relative risks (RR) or prevalence ratios (PR) has represented a statistical challenge in multivariate analysis and, furthermore, some researchers do not have access to the available methods. Objective: To propose and evaluate a new method for estimating RR and PR by logistic regression.
A provisional database was designed in which events were duplicated but identified as non-events. After, a logistic regression was performed and effect measures were calculated, which were considered RR estimations. This method was compared with binomial regression, Cox regression with robust variance and ordinary logistic regression in analyses with three outcomes of different frequencies.
ORs estimated by ordinary logistic regression progressively overestimated RRs as the outcome frequency increased. RRs estimated by Cox regression and the method proposed in this article were similar to those estimated by binomial regression for every outcome. However, confidence intervals were wider with the proposed method.
This simple tool could be useful for calculating the effect of risk factors and the impact of health interventions in developing countries when other statistical strategies are not available.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In a low-income country like Bangladesh, where the poverty rate is higher in rural compared to urban areas, the consistent use of sanitary latrines over time is a challenge. To address this issue, the Water, Sanitation, and Hygiene (WASH) program of the Bangladesh Rural Advancement Committee (BRAC) was devised to improve health of the rural poor through enhanced sanitation services, such as by providing loans or education. Sanitary latrine use in households and changes over time were assessed in this study.
    BMC Public Health 07/2014; 14(1):721. DOI:10.1186/1471-2458-14-721 · 2.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the last decades, it has been discussed the use of epidemiological prevalence ratio (PR) rather than odds ratio as a measure of association to be estimated in cross-sectional studies. The main difficulties in use of statistical models for the calculation of PR are convergence problems, availability of adequate tools and strong assumptions. The goal of this study is to illustrate how to estimate PR and its confidence interval directly from logistic regression estimates. We present three examples and compare the adjusted estimates of PR with the estimates obtained by use of log-binomial, robust Poisson regression and adjusted prevalence odds ratio (POR). The marginal and conditional prevalence ratios estimated from logistic regression showed the following advantages: no numerical instability; simple to implement in a statistical software; and assumes the adequate probability distribution for the outcome.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background and Objectives: The aim of this study was to examine the hypothesis that pentraxin 3 (PTX3) can have a diagnostic value for predicting anatomical complexity of coronary artery stenosis as measured by the Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX) score. Subjects and Methods: We investigated the association of systemic arterial PTX3 with SYNTAX score among 500 patients with ischemic heart disease assigned to medical treatment (251), percutaneous coronary intervention (PCI) (197), or coronary artery bypass graft (CABG) (52). Results: The clinical judgment of the cardiologists was near-perfectly concordant with the SYNTAX score. Mean {99% confidence intervals (CIs)} SYNTAX scores were 5.8 (5.1-6.6), 18.4 (17.1-19.8), and 33.2 (32.8-33.6) in patients assigned to medical therapy, PCI, and CABG, respectively. The AROC (95% CIs) for discriminating between patients with and without a high SYNTAX score (> 23) was 0.920 (0.895-0.946) for systemic arterial levels of PTX3. As the systemic arterial level of PTX3 increased, the SYNTAX scores also increased almost in a curvilinear fashion, with the value corresponding to the SYNTAX score of 23 being 0.29 ng . dL(-1). This cutpoint achieved a sensitivity of 0.66 (0.57-0.74), a specificity of 0.94 (0.91-0.96), a positive predictive value of 0.79 (0.70-0.87), and a negative predictive value of 0.89 (0.85-0.92). Conclusion: We observed that systemic arterial levels of PTX3 were associated with the SYNTAX score in a curvilinear fashion. The discriminatory power of systemic arterial levels of PTX3 for a high SYNTAX score was excellent. The interesting finding of this study was the near perfect concordance between the decisions made by the cardiologists based on their clinical judgment and the SYNTAX score. The systemic arterial PTX3 level of 0.29 ng . dL(-1) was highly specific for diagnosing complex coronary artery stenosis.
    Korean Circulation Journal 07/2014; 44(4):220-6. DOI:10.4070/kcj.2014.44.4.220

Full-text (3 Sources)

Available from
Jun 4, 2014