Medical Statistics. Introduction. What do you hope to get out of this course in Medical Statistics? Motivation

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1 Medical Statistics Introduction Motivation What do you hope to get out of this course in Medical Statistics? 3 reasons to study Medical Statistics (for yourself and your patients) 10 statistical concepts or terms that you often hear and do not understand

2 Example: Male circumcision and HIV (course pack page ) What does Evidence Based Medicine mean? A method to assure patients receive the most effective treatment (with the least side-effects). The strength of evidence favouring a specific treatment should be clearly stated. H.G. Wells voiced the following prophecy at the end of the 1800s: Statistical thinking will one day be as necessary for efficient citizenship as the ability to read and write. The growing need for statistical literacy Information age : we are bombarded with statistics by the media, and the need to be discriminating is crucial. Statistical thinking underlies many important decisions in society: we must understand if we are to contribute/challenge.

3 Statistics in the media Surveys Road/rail/air accidents Risks (e.g. food, radiation) Opinion polls Results of medical research From What is newsworthy? Longitudinal study of the reporting of medical research in two British newspapers, BMJ Nov 2005 See course pack Surveys of varying reliability: some (e.g. political opinion polls) are based on good methodology, but some based on convenient group people e.g. phone-in survey or internet survey Reports of medical research may refer to published research, but may provide their own spin. Sometimes no reference at all, just research shows.!! Reports in media emphasise results: Example from The Guardian, 19 May 1988 reporting on a study of longevity and left-handedness This gives the impression that statistics is only about calculations and presentation of results, without regard to how results are arrived at. In fact, statistics involves a lot more, including: Why and how the study was done How the data was collected If you re over 80 and lefthanded, you re in a class of your own. Nearly all the other left-handers have passed on.it was, said Dr. Halpern last night, a small sample. Generally the scientists found that there was no difference in death rates up to age 33; from then on left-handers slowly fade away. She offered several reasons. One might be that lowweight babies tended to be left-handed, and low birthweight might mean reduced chances of survival. The other was that it was a right-handed world. The lefthanded were simply at a disadvantage with automobiles and power tools, suffered from greater stress and had more accidents.

4 Example from The Guardian, May 1988 (continued) reporting on a study of longevity and left-handedness Many weaknesses in the study that affect the validity of these interpretations (we will learn how to recognise). Note that findings are reported uncritically by the newspaper. Variation in reliability of reports in the media leads to controversies in medical research that often have an impact on daily life and the public become confused We will check later how accurately the newspaper reports. Examples of statistics in society Statistics in Medical Practice DNA fingerprinting (paternity testing, criminal investigation) Statistical Methods enable us to weigh the evidence from research for: Court Cases e.g. expert witnesses Industrial quality control Water and food safety Statistical methods are necessary to quantify uncertainty so that reasonable decisions can be made New treatments New diagnostic tests Patient management/prognosis Health interventions Possible size outbreaks (e.g. AIDS, SARS, hospital infections) Resource allocation (staff, beds, equipment) Vaccination uptake Etc. etc. we need basic statistical literacy to be able to offer safe, up-to-date advice and treatment to our patients..

5 The special need for statistical literacy for doctors Theme Doctor, what is wrong with me? Is there a treatment? Critical Appraisal of: Diagnostic Tests RCT Statistical Methods/Skills Simple rules of Probability Sensitivity, Specificity, Predictive Value Randomised Trials Could it have been prevented? Is it common? Why me? Will I be cured? Intervention trials Observational Studies (prevalence, risk factors) Prognosis studies Intervention trials Study Designs: (Cross-sectional, Cohort, Case-Control) Prognosis/survival Analysis Accumulating the evidence Systematic Reviews Meta-Analysis,