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Edward G. Miner Library

Med Students: Phase 1: Session 3: Appraise, Apply, and Assess

This guide will serve as an information resource for first year medical students at the University of Rochester School of Medicine and Dentistry

Appraise, Assess, Apply

Learning Objectives:

  • Become familiar with additional foreground tools
  • Understand the basics of critical appraisal
  • Hands-on application of appraising

Key Resources 

Point of Care Tools

For videos on using these tools see the Clinical Tools tab under MEI

Reading a Paper

Evidence Based Medicine Books

Spotting Bad Science

Illustration describing how to recognize bad science

Critical Appraisal

There are many useful resources about how to read specific papers (i.e. therapy, preventative screening, systematic reviews…etc.

For example, The Oxford Centre for Evidence-Based Medicine (CEBM) develops, teaches, promotes, and disseminates better evidence for health care.

  • Finding the evidence: a how-to guide- 1 - Using PICO to formulate a search question. 2 - Turning search terms into a search strategy. 3 - Turning your search strategy into results (searching PubMed).
  • Critical Appraisal tools- Critical appraisal worksheets to help you appraise the reliability, importance, and applicability of clinical evidence.
  •  Number Needed to Treat (NNT)- The Number Needed to Treat (NNT) is the number of patients you need to treat to prevent one additional bad outcome (death, stroke, etc.).
  • Likelihood Ratios- The Likelihood Ratio (LR) is the likelihood that a given test result would be expected in a patient with the target disorder compared to the likelihood that that same result would be expected in a patient without the target disorder.
  • Study designs- A guide to the different study types and a comparison of the pros and cons

There are several sources for free, downloadable critical appraisal worksheets or checklists.  These worksheets guide you through the steps of critical appraisal. Worksheets are tailored to the type of study being appraised. 

  • Critical Appraisal Worksheet by CEBM Centre for Evidence-based Medicine provides useful tools and downloads for the critical appraisal of different types of medical evidence. Example appraisal sheets are provided together with several helpful examples.
  • CASP Checklists This set of eight (8) critical appraisal tools are designed to be used when reading research, these include tools for Systematic Reviews, Randomized Controlled Trials, Cohort Studies, Case-Control Studies, Economic Evaluations, Diagnostic Studies, Qualitative studies, and Clinical Prediction Rule.
  • Knowledge Translation Program (Toronto) Critical appraisal worksheets from the Centre for Evidence-Based Medicine Toronto, including the worksheets for diagnosis, harm, prognosis, systematic review, and therapy.

Study Types Explained

Definitions of Study Types

 (From the Centre for Evidence Based MedicineOCEBM Table of Evidence Glossary.) 

 Meta-analysis: A statistical technique that summarizes the results of several studies in a single weighted estimate, in which more weight is given to results of studies with more events and sometimes to studies of higher quality.

Systematic Review: The application of strategies that limit bias in the assembly, critical appraisal, and synthesis of all relevant studies on a specific topic. Systematic reviews focus on peer-reviewed publications about a specific health problem and use rigorous, standardized methods for selecting and assessing articles. A systematic review may or may not include a meta-analysis, which is a quantitative summary of the results.

Randomized Controlled Trial: An epidemiological experiment in which subjects in a population are randomly assigned into groups, usually called study and control groups, to receive or not receive an experimental preventive or therapeutic procedure, maneuver, or intervention. The results are assessed by rigorous comparison of rates of disease, death, recovery, or other appropriate outcome in the study and control groups.

Controlled Clinical Trial: a trial in which participants are assigned to two or more different treatment groups.  When the method of allocation is by random selection, the study is referred to as a randomized controlled trial (RCT). Non-randomized controlled trials are more likely to suffer from bias than RCTs.

Cohort study: The analytic method of epidemiologic study in which subsets of a defined population (e.g. smokers) can be identified who are, have been, or in the future may be exposed or not exposed, or exposed in different degrees, to a factor or factors hypothesized to influence the probability of occurrence of a given disease (e.g. lung cancer) or other outcome. The main feature of cohort study is observation of large numbers over a long period (commonly years) with comparison of incidence rates in groups that differ in exposure levels.

Cross-Sectional Survey: A study that examines the relationship between diseases (or other health-related characteristics) and other variables of interest as they exist in a defined population at one particular time (ie exposure and outcomes are both measured at the same time). Best for quantifying the prevalence of a disease or risk factor, and for quantifying the accuracy of a diagnostic test.

Case-control study: The observational epidemiologic study of persons with the disease (or other outcome variable) of interest and a suitable control (comparison, reference) group of persons without the disease. The relationship of an attribute to the disease is examined by comparing the diseased and nondiseased with regard to how frequently the attribute is present or, if quantitative, the levels of the attribute, in each of the groups.

Case-series: A group or series of case reports involving patients who were given similar treatment. Reports of case series usually contain detailed information about the individual patients. This includes demographic information (for example, age, gender, ethnic origin) and information on diagnosis, treatment, response to treatment, and follow-up after treatment. (NCI Dictionary)

Levels of Evidence and Study Designs

 Click the image to enlarge it.Illustration of the EBM Levels of Evidence Pyramid with descriptions of each type of study