BASIC CONCEPTS in EPIDEMIOLOGY Introduction
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Descriptive Statistics (Part 2): Interpreting Study Results
Statistical Notes II Descriptive statistics (Part 2): Interpreting study results A Cook and A Sheikh he previous paper in this series looked at ‘baseline’. Investigations of treatment effects can be descriptive statistics, showing how to use and made in similar fashion by comparisons of disease T interpret fundamental measures such as the probability in treated and untreated patients. mean and standard deviation. Here we continue with descriptive statistics, looking at measures more The relative risk (RR), also sometimes known as specific to medical research. We start by defining the risk ratio, compares the risk of exposed and risk and odds, the two basic measures of disease unexposed subjects, while the odds ratio (OR) probability. Then we show how the effect of a disease compares odds. A relative risk or odds ratio greater risk factor, or a treatment, can be measured using the than one indicates an exposure to be harmful, while relative risk or the odds ratio. Finally we discuss the a value less than one indicates a protective effect. ‘number needed to treat’, a measure derived from the RR = 1.2 means exposed people are 20% more likely relative risk, which has gained popularity because of to be diseased, RR = 1.4 means 40% more likely. its clinical usefulness. Examples from the literature OR = 1.2 means that the odds of disease is 20% higher are used to illustrate important concepts. in exposed people. RISK AND ODDS Among workers at factory two (‘exposed’ workers) The probability of an individual becoming diseased the risk is 13 / 116 = 0.11, compared to an ‘unexposed’ is the risk. -
Risk Factors Associated with Maternal Age and Other Parameters in Assisted Reproductive Technologies - a Brief Review
Available online at www.pelagiaresearchlibrary.com Pelagia Research Library Advances in Applied Science Research, 2017, 8(2):15-19 ISSN : 0976-8610 CODEN (USA): AASRFC Risk Factors Associated with Maternal Age and Other Parameters in Assisted Reproductive Technologies - A Brief Review Shanza Ghafoor* and Nadia Zeeshan Department of Biochemistry and Biotechnology, University of Gujrat, Hafiz Hayat Campus, Gujrat, Punjab, Pakistan ABSTRACT Assisted reproductive technology is advancing at fast pace. Increased use of ART (Assisted reproductive technology) is due to changing living standards which involve increased educational and career demand, higher rate of infertility due to poor lifestyle and child conceivement after second marriage. This study gives an overview that how advancing age affects maternal and neonatal outcomes in ART (Assisted reproductive technology). Also it illustrates how other factor like obesity and twin pregnancies complicates the scenario. The studies find an increased rate of preterm birth .gestational hypertension, cesarean delivery chances, high density plasma, Preeclampsia and fetal death at advanced age. The study also shows the combinatorial effects of mother age with number of embryos along with number of good quality embryos which are transferred in ART (Assisted reproductive technology). In advanced age women high clinical and multiple pregnancy rate is achieved by increasing the number along with quality of embryos. Keywords: Reproductive techniques, Fertility, Lifestyle, Preterm delivery, Obesity, Infertility INTRODUCTION Assisted reproductive technology actually involves group of treatments which are used to achieve pregnancy when patients are suffering from issues like infertility or subfertility. The treatments can involve invitro fertilization [IVF], intracytoplasmic sperm injection [ICSI], embryo transfer, egg donation, sperm donation, cryopreservation, etc., [1]. -
Clarifying Questions About “Risk Factors”: Predictors Versus Explanation C
Schooling and Jones Emerg Themes Epidemiol (2018) 15:10 Emerging Themes in https://doi.org/10.1186/s12982-018-0080-z Epidemiology ANALYTIC PERSPECTIVE Open Access Clarifying questions about “risk factors”: predictors versus explanation C. Mary Schooling1,2* and Heidi E. Jones1 Abstract Background: In biomedical research much efort is thought to be wasted. Recommendations for improvement have largely focused on processes and procedures. Here, we additionally suggest less ambiguity concerning the questions addressed. Methods: We clarify the distinction between two confated concepts, prediction and explanation, both encom- passed by the term “risk factor”, and give methods and presentation appropriate for each. Results: Risk prediction studies use statistical techniques to generate contextually specifc data-driven models requiring a representative sample that identify people at risk of health conditions efciently (target populations for interventions). Risk prediction studies do not necessarily include causes (targets of intervention), but may include cheap and easy to measure surrogates or biomarkers of causes. Explanatory studies, ideally embedded within an informative model of reality, assess the role of causal factors which if targeted for interventions, are likely to improve outcomes. Predictive models allow identifcation of people or populations at elevated disease risk enabling targeting of proven interventions acting on causal factors. Explanatory models allow identifcation of causal factors to target across populations to prevent disease. Conclusion: Ensuring a clear match of question to methods and interpretation will reduce research waste due to misinterpretation. Keywords: Risk factor, Predictor, Cause, Statistical inference, Scientifc inference, Confounding, Selection bias Introduction (2) assessing causality. Tese are two fundamentally dif- Biomedical research has reached a crisis where much ferent questions, concerning two diferent concepts, i.e., research efort is thought to be wasted [1]. -
Limitations of the Odds Ratio in Gauging the Performance of a Diagnostic, Prognostic, Or Screening Marker
American Journal of Epidemiology Vol. 159, No. 9 Copyright © 2004 by the Johns Hopkins Bloomberg School of Public Health Printed in U.S.A. All rights reserved DOI: 10.1093/aje/kwh101 Limitations of the Odds Ratio in Gauging the Performance of a Diagnostic, Prognostic, or Screening Marker Margaret Sullivan Pepe1,2, Holly Janes2, Gary Longton1, Wendy Leisenring1,2,3, and Polly Newcomb1 1 Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA. 2 Department of Biostatistics, University of Washington, Seattle, WA. 3 Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, WA. Downloaded from Received for publication June 24, 2003; accepted for publication October 28, 2003. A marker strongly associated with outcome (or disease) is often assumed to be effective for classifying persons http://aje.oxfordjournals.org/ according to their current or future outcome. However, for this assumption to be true, the associated odds ratio must be of a magnitude rarely seen in epidemiologic studies. In this paper, an illustration of the relation between odds ratios and receiver operating characteristic curves shows, for example, that a marker with an odds ratio of as high as 3 is in fact a very poor classification tool. If a marker identifies 10% of controls as positive (false positives) and has an odds ratio of 3, then it will correctly identify only 25% of cases as positive (true positives). The authors illustrate that a single measure of association such as an odds ratio does not meaningfully describe a marker’s ability to classify subjects. Appropriate statistical methods for assessing and reporting the classification power of a marker are described. -
Guidance for Industry E2E Pharmacovigilance Planning
Guidance for Industry E2E Pharmacovigilance Planning U.S. Department of Health and Human Services Food and Drug Administration Center for Drug Evaluation and Research (CDER) Center for Biologics Evaluation and Research (CBER) April 2005 ICH Guidance for Industry E2E Pharmacovigilance Planning Additional copies are available from: Office of Training and Communication Division of Drug Information, HFD-240 Center for Drug Evaluation and Research Food and Drug Administration 5600 Fishers Lane Rockville, MD 20857 (Tel) 301-827-4573 http://www.fda.gov/cder/guidance/index.htm Office of Communication, Training and Manufacturers Assistance, HFM-40 Center for Biologics Evaluation and Research Food and Drug Administration 1401 Rockville Pike, Rockville, MD 20852-1448 http://www.fda.gov/cber/guidelines.htm. (Tel) Voice Information System at 800-835-4709 or 301-827-1800 U.S. Department of Health and Human Services Food and Drug Administration Center for Drug Evaluation and Research (CDER) Center for Biologics Evaluation and Research (CBER) April 2005 ICH Contains Nonbinding Recommendations TABLE OF CONTENTS I. INTRODUCTION (1, 1.1) ................................................................................................... 1 A. Background (1.2) ..................................................................................................................2 B. Scope of the Guidance (1.3)...................................................................................................2 II. SAFETY SPECIFICATION (2) ..................................................................................... -
Journal of Clinical Trails Market Analysis Advances in Clinical Research and Clinical Trials 2020
Journal of Clinical Trails Market Analysis Advances in Clinical Research and Clinical Trials 2020 Raymond Chong The research report on Global Clinical Trials Market 2019 Other prominent players in the value chain include Mednet keenly analyzes significant features of the industry. The Solutions, Arisglobal, eClinForce Inc., DZS Software Solutions, DSG, analysis servers market size, latest trends, drivers, threats, Inc., Guger Technologies Inc., ICON, Plc., ChemWare Inc., and opportunities, as well as key market segments. It is based on iWeb Technologies Limited. past data and present market needs. Also, involve distinct business approaches accepted by the decision makers. Those intensify growth and make a remarkable stand in the industry. The Clinical Trials market will grow with a significant CAGR between 2019 to 2028. The report segregates the complete market on the basis of key players, geographical areas, and segments. Increasing demand for new medical equipments and medicines among end users, coupled with growing investment for research and development activities for development of effective medicines are major factors driving growth of the global clinical trials market. In addition, increasing number of individuals suffering from chronic diseases as well as changing The clinical trials market is projected to arrive at USD 1.76 conditions and nature of certain types of chronic diseases is billion by 2025, from USD 1.04 billion in 2017 growing at a another factor anticipated to support growth of the global CAGR of 6.7 percent from 2018 to 2025. An upcoming clinical trials market to significant extent. market report contains data for historic year 2016, and the base year of calculation is 2017. -
The Statistical Significance of Randomized Controlled Trial Results Is Frequently Fragile: a Case for a Fragility Index
The statistical significance of randomized controlled trial results is frequently fragile: A case for a Fragility Index Walsh, M., Srinathan, S. K., McAuley, D. F., Mrkobrada, M., Levine, O., Ribic, C., Molnar, A. O., Dattani, N. D., Burke, A., Guyatt, G., Thabane, L., Walter, S. D., Pogue, J., & Devereaux, P. J. (2014). The statistical significance of randomized controlled trial results is frequently fragile: A case for a Fragility Index. Journal of Clinical Epidemiology, 67(6), 622-628. https://doi.org/10.1016/j.jclinepi.2013.10.019 Published in: Journal of Clinical Epidemiology Document Version: Publisher's PDF, also known as Version of record Queen's University Belfast - Research Portal: Link to publication record in Queen's University Belfast Research Portal Publisher rights 2014 The Authors. Published by Elsevier Inc. This is an open access article published under a Creative Commons Attribution-NonCommercial-NoDerivs License (https://creativecommons.org/licenses/by-nc-nd/3.0/), which permits distribution and reproduction for non-commercial purposes, provided the author and source are cited. General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made to ensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. -
Why Do You Need a Biostatistician? Antonia Zapf1* , Geraldine Rauch2 and Meinhard Kieser3
Zapf et al. BMC Medical Research Methodology (2020) 20:23 https://doi.org/10.1186/s12874-020-0916-4 DEBATE Open Access Why do you need a biostatistician? Antonia Zapf1* , Geraldine Rauch2 and Meinhard Kieser3 Abstract The quality of medical research importantly depends, among other aspects, on a valid statistical planning of the study, analysis of the data, and reporting of the results, which is usually guaranteed by a biostatistician. However, there are several related professions next to the biostatistician, for example epidemiologists, medical informaticians and bioinformaticians. For medical experts, it is often not clear what the differences between these professions are and how the specific role of a biostatistician can be described. For physicians involved in medical research, this is problematic because false expectations often lead to frustration on both sides. Therefore, the aim of this article is to outline the tasks and responsibilities of biostatisticians in clinical trials as well as in other fields of application in medical research. Keywords: Medical research, Biostatistician, Tasks, Responsibilities Background Biometric Society (IBS) provides a definition of biomet- What is a biostatistician, what does he or she actually do rics as a ‘field of development of statistical and mathem- and what distinguishes him or her from, for example, an atical methods applicable in the biological sciences’ [2]. epidemiologist? If we would ask this our main cooper- In here, we will focus on (human) medicine as area of ation partners like physicians or biologists, they probably application, but the results can be easily transferred to could not give a satisfying answer. This is problematic the other biological sciences like, for example, agricul- because false expectations often lead to frustration on ture or ecology. -
Understanding Relative Risk, Odds Ratio, and Related Terms: As Simple As It Can Get Chittaranjan Andrade, MD
Understanding Relative Risk, Odds Ratio, and Related Terms: As Simple as It Can Get Chittaranjan Andrade, MD Each month in his online Introduction column, Dr Andrade Many research papers present findings as odds ratios (ORs) and considers theoretical and relative risks (RRs) as measures of effect size for categorical outcomes. practical ideas in clinical Whereas these and related terms have been well explained in many psychopharmacology articles,1–5 this article presents a version, with examples, that is meant with a view to update the knowledge and skills to be both simple and practical. Readers may note that the explanations of medical practitioners and examples provided apply mostly to randomized controlled trials who treat patients with (RCTs), cohort studies, and case-control studies. Nevertheless, similar psychiatric conditions. principles operate when these concepts are applied in epidemiologic Department of Psychopharmacology, National Institute research. Whereas the terms may be applied slightly differently in of Mental Health and Neurosciences, Bangalore, India different explanatory texts, the general principles are the same. ([email protected]). ABSTRACT Clinical Situation Risk, and related measures of effect size (for Consider a hypothetical RCT in which 76 depressed patients were categorical outcomes) such as relative risks and randomly assigned to receive either venlafaxine (n = 40) or placebo odds ratios, are frequently presented in research (n = 36) for 8 weeks. During the trial, new-onset sexual dysfunction articles. Not all readers know how these statistics was identified in 8 patients treated with venlafaxine and in 3 patients are derived and interpreted, nor are all readers treated with placebo. These results are presented in Table 1. -
Outcome Reporting Bias in COVID-19 Mrna Vaccine Clinical Trials
medicina Perspective Outcome Reporting Bias in COVID-19 mRNA Vaccine Clinical Trials Ronald B. Brown School of Public Health and Health Systems, University of Waterloo, Waterloo, ON N2L3G1, Canada; [email protected] Abstract: Relative risk reduction and absolute risk reduction measures in the evaluation of clinical trial data are poorly understood by health professionals and the public. The absence of reported absolute risk reduction in COVID-19 vaccine clinical trials can lead to outcome reporting bias that affects the interpretation of vaccine efficacy. The present article uses clinical epidemiologic tools to critically appraise reports of efficacy in Pfzier/BioNTech and Moderna COVID-19 mRNA vaccine clinical trials. Based on data reported by the manufacturer for Pfzier/BioNTech vaccine BNT162b2, this critical appraisal shows: relative risk reduction, 95.1%; 95% CI, 90.0% to 97.6%; p = 0.016; absolute risk reduction, 0.7%; 95% CI, 0.59% to 0.83%; p < 0.000. For the Moderna vaccine mRNA-1273, the appraisal shows: relative risk reduction, 94.1%; 95% CI, 89.1% to 96.8%; p = 0.004; absolute risk reduction, 1.1%; 95% CI, 0.97% to 1.32%; p < 0.000. Unreported absolute risk reduction measures of 0.7% and 1.1% for the Pfzier/BioNTech and Moderna vaccines, respectively, are very much lower than the reported relative risk reduction measures. Reporting absolute risk reduction measures is essential to prevent outcome reporting bias in evaluation of COVID-19 vaccine efficacy. Keywords: mRNA vaccine; COVID-19 vaccine; vaccine efficacy; relative risk reduction; absolute risk reduction; number needed to vaccinate; outcome reporting bias; clinical epidemiology; critical appraisal; evidence-based medicine Citation: Brown, R.B. -
Using a Study on Arsenic Ingestion and Bladder Cancer As an Example How-Ran Guo1,2,3
Guo BMC Public Health 2011, 11:820 http://www.biomedcentral.com/1471-2458/11/820 RESEARCHARTICLE Open Access Age adjustment in ecological studies: using a study on arsenic ingestion and bladder cancer as an example How-Ran Guo1,2,3 Abstract Background: Despite its limitations, ecological study design is widely applied in epidemiology. In most cases, adjustment for age is necessary, but different methods may lead to different conclusions. To compare three methods of age adjustment, a study on the associations between arsenic in drinking water and incidence of bladder cancer in 243 townships in Taiwan was used as an example. Methods: A total of 3068 cases of bladder cancer, including 2276 men and 792 women, were identified during a ten-year study period in the study townships. Three methods were applied to analyze the same data set on the ten-year study period. The first (Direct Method) applied direct standardization to obtain standardized incidence rate and then used it as the dependent variable in the regression analysis. The second (Indirect Method) applied indirect standardization to obtain standardized incidence ratio and then used it as the dependent variable in the regression analysis instead. The third (Variable Method) used proportions of residents in different age groups as a part of the independent variables in the multiple regression models. Results: All three methods showed a statistically significant positive association between arsenic exposure above 0.64 mg/L and incidence of bladder cancer in men and women, but different results were observed for the other exposure categories. In addition, the risk estimates obtained by different methods for the same exposure category were all different. -
Sensitivity and Specificity. Wikipedia. Last Modified on 16 November 2013
Sensitivity and specificity - Wikipedia, the free encyclopedia Create account Log in Article Talk Read Edit View Sensitivity and specificity From Wikipedia, the free encyclopedia Main page Contents Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as Featured content classification function. Sensitivity (also called the true positive rate, or the recall rate in some fields) measures the proportion of Current events actual positives which are correctly identified as such (e.g. the percentage of sick people who are correctly identified as having Random article the condition). Specificity measures the proportion of negatives which are correctly identified as such (e.g. the percentage of Donate to Wikipedia healthy people who are correctly identified as not having the condition, sometimes called the true negative rate). These two measures are closely related to the concepts of type I and type II errors. A perfect predictor would be described as 100% Interaction sensitive (i.e. predicting all people from the sick group as sick) and 100% specific (i.e. not predicting anyone from the healthy Help group as sick); however, theoretically any predictor will possess a minimum error bound known as the Bayes error rate. About Wikipedia For any test, there is usually a trade-off between the measures. For example: in an airport security setting in which one is testing Community portal for potential threats to safety, scanners may be set to trigger on low-risk items like belt buckles and keys (low specificity), in Recent changes order to reduce the risk of missing objects that do pose a threat to the aircraft and those aboard (high sensitivity).