Basic Research Methods - Overview | PDF

BASIC RESEARCH METHODS OBJECTIVES Recall the tasks of Evidence Based Medicine Understand the components of creating a research question Define different types of research design Identify what specific research questions can be answered by a variety of research designs REMEMBER FROM WEEK...

BASIC RESEARCH METHODS OBJECTIVES Recall the tasks of Evidence Based Medicine Understand the components of creating a research question Define different types of research design Identify what specific research questions can be answered by a variety of research designs REMEMBER FROM WEEK 1: TASKS OF EVIDENCE-BASED MEDICINE: 1. Asking the clinical question 2. Searching for the evidence that addresses the question 3. Assessing the quality of the evidence 4. Incorporating the evidence into a clinical decision 5. Evaluating the process  TASK 1- ASKING A CLINICAL QUESTION: BACKGROUND VS. FOREGROUND QUESTIONS Background Questions: General questions that provide background information on a particular topic Example: What are the risk factors for osteoporosis? What is the incidence of Lyme disease in Pennsylvania? Foreground Questions: Specific questions designed to provide guidance for clinical care of a particular patient or group Example: In children less than 8 years of age, what antibiotic regimen is most effective for recovery of Lyme Disease with less side effect? ELEMENTS OF A RESEARCH QUESTION: PICO(T) How would the patient or population be described? Population Allows readers to understand the research population and whether it is sufficiently similar to their patient population Intervention What will be done for the patient? Is this an intervention or exposure? (Exposure) Example: Medication, procedure, diagnostic test What are you comparing the intervention against? (i.e: What are alternative approaches?) Comparison Examples: placebo, a standard intervention, non-exposed population There can be more than one comparison group Outcome What is the clinician hoping to measure, achieve or affect? When will the outcome be measured? Timing Example: Two trials with 2 different follow-up periods could give you 2 very different results PICO QUESTIONS CAN BE USED TO ADDRESS A VARIETY OF CLINICAL QUESTION TYPES: DIAGNOSIS, ETIOLOGY OR HARM, PROGNOSIS, TREATMENT Ritsema, et al. Ballweg's Physician Assistant A Guide to Clinical Practice LET'S PRACTICE IMPORTANT TERMS Prevalence: proportion of persons affected with a particular disease/condition at a specific time Incidence: the number of new cases of disease that occur during a specified period, expressed as a proportion of the number of people at risk during that time Association: statistical techniques to quantify the strength of the relationship between two or more variables Causation: exposure produces the effect (presence of an adverse exposure, absence of a preventative exposure) Correlation: the magnitude of the association between 2 variables (the strength sometimes expressed by correlation coefficient)  TASK 2- SEARCHING THE EVIDENCE Divided into 2 categories: Filtered Evidence: already gathered and synthesized by experts into a format that is readily usable by clinicians Clinical Guidelines: US Preventive Services Task Force , American Cancer Society Guidelines Evidence Based Summaries: UpToDate Systematic Reviews Databases Unfiltered Evidence: original research articles published in peer-reviewed journal Use PICO(T) components to complete a systematic literature search Use databases such as PubMed, Ovid **Recall Rose Turner's talk on how to search PubMed for original research (Week 3) TASK 2B: UNDERSTANDING RESEARCH DESIGN Once primary literature search is completed, one must assess the articles for usefulness and validity Study design is important feature of research studies that affects validity of that research Validity: how well the results among the study participants represent true findings among similar individuals outside of the study Many types of study design that have benefits and weaknesses  All studies Is there a NO comparis YES on group? Descriptive Analytic Can you control exposure ? Survey Qualitative Experiment YES NO Observatio al nal Analytic Randomize Cohort d Parallel Study Group STUDY Randomize d Crossover Cross Sectional (Analytic) DESIGN Case- Control Study  DESCRIPTIVE STUDIES Describes a population and outcomes (PO) No comparison of 2 groups (C). Focus on describing the characteristics, presentation and outcomes of a specific patient or small cohort of similar patients Examples: Case reports, case-series, qualitative studies and survey Disadvantages: Since no comparison group, you can only hypothesize why certain outcomes, presentations, characteristics are seen Lowest strength of evidence  ANALYTIC STUDIES Quantify relationship between two factors -> look at the effect of an intervention (I) or exposure (E) on an outcome (O) in comparison (C) groups. If researcher actively changes a factor or imposes an intervention -> experimental Example: randomized control trial If researcher has passive involvement -> observational Observational studies can be: Retrospective: outcome already occurred prior to start of the study; therefore, researcher is looking back in time Prospective: the outcome has yet to occur prior to the start of the study Example: case control and cohort studies EXPERIMENTAL: RANDOMIZED CONTROL TRIAL Participants are divided into treatment/intervention or control/placebo groups using a random mechanism Best for studying the effect of an intervention or exposure Advantages: Unbiased distribution of confounders Blinding more likely Randomization facilitates statistical analysis Disadvantages: Expensive: time and money Volunteer bias Ethically problematic at times  EXPERIMENTAL: RANDOMIZED CROSSOVER Control trial where each study participant has both therapies Advantages: All subjects serve as own controls Error variance is reduced, thus reducing sample size needed All subjects receive treatment Blinding can be maintained Crossover trials: what are they and what are their advantages a nd limitations? - Students 4 Best Evidence (cochrane.org) Disadvantages: All subjects receive placebo or alternative treatment at some point Washout period lengthy between treatment A and treatment B Cannot be use for treatments with permanent effects  OBSERVATIONAL: COHORT STUDY A group of people with a common characteristic (cohort) are gathered, participants are divided into two or more groups based on their level of exposure to the independent variable of interest Participants are followed over time to see who develops the outcome of interest Typically prospective Advantages: Likely strongest study type if randomization is not possible Ethically safe Can measure multiple outcomes Easier and cheaper than RCT Disadvantages: Confounding may occur due to lack of randomization No causation, only correlation Blinding difficult Large sample size or long follow-up necessary  OBSERVATIONAL: CASE-CONTROL STUDIES Look at population with a certain outcome or disease (cases) vs similar population (control) without the outcome or disease. Then, information is obtained on whether the subjects have been exposed to the factor under investigation. Typically retrospective Advantages: Quick and Inexpensive Good for rare disease/disorder Disadvantages: Confounders Potential bias: recall, selection No causal relationship can be established Cohort Study Case Control Study OBSERVATIONAL: CROSS-SECTIONAL STUDY "Snap-shot" or "slice in time" study 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 Best for quantifying the prevalence (not incidence) of a disease or risk factor, and for quantifying the accuracy of a diagnostic test Advantages: Inexpensive, ethically safe Disadvantages: No causal relationship able to be drawn. Can only establish association. Recall bias Confounders may be unequally distributed Group sizes may be unequal HIERARCHY OF STUDY DESIGN Meta- analysis Experimental Observational (cohort > case control) Descriptive Studies LET'S PRACTICE REFERENCES Ritsema, T, et al. Ballweg’s Physician Assistant : A Guide to Clinical Practice, 7th Ed. Elsevier, Inc. 2022. Guyatt, G, Rennie, D, Meade, M, Cook, D. Users’ Guides to the Medical Literature Essentials of Evidence-Based Clinical Practice, 3rd Ed. McGraw-Hill Education. 2015. Centre for Evidence-Based Medicine: Study designs — Centre for Evidence-Based Medicine (CEBM), University of Oxford Aggarwal R, Ranganathan P. Study designs: Part 2 - Descriptive studies. Perspect Clin Res. 2019;10(1):34-36. doi:10.4103/picr.PICR_154_18 HSLS EBM Resources: http://hsls.libguides.com/pyramid