Evidence-Based Dentistry Lecture 2 PDF

Evidence-based dentistry Lecture 2: Introduction to study designs  Case study Types of epidemiological studies Descriptive...

Evidence-based dentistry Lecture 2: Introduction to study designs  Case study Types of epidemiological studies Descriptive Case series Observational studies Cross sectional Analytical Cohort Non-randomized Case control experimental controlled trials studies Randomized controlled trials Systematic reviews Literature reviews Meta-analysis  1. Case study or report: It’s a detailed study of a specific case A case study is a qualitative research method that involves the in-depth exploration and analysis of a particular case, which can be an individual, group, organization, event, or community. Advantages: Limitations: - Help to generate hypotheses about the causal - Limited generalizability relationships between different factors and - Biased sampling outcomes - Limited control - Document certain phenomenon, symptom or a - Resources intensive rare drug reaction - informing practice or policy - Provide rich data and a holistic perspective How to write a case report: step 1: Select a case Once you have developed your problem statement and research questions, you should be ready to choose the specific case that you want to focus on. Step 2: Build a theoretical framework While case studies focus more on concrete details than general theories, they should usually have some connection with theory, This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to: Exemplify a theory by showing how it explains the case under investigation Expand on a theory by uncovering new concepts and ideas that need to be incorporated Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions Step 3: Collect your data There are many different research methods you can use to collect data on your subject. Step 4: Describe and analyze the case In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject. 1. Case study or report: 2. Case series: It tracks a group of patients with a similar condition or treatment. It's often used to: Describe a new disease or condition, Identify unique symptoms, characteristics, or progression patterns, Report on the effectiveness of a new treatment, Observe outcomes Advantages: - Observational - Descriptive - Retrospective or prospective - Usually a seed for RCT Limitations: - No control group: This makes it difficult to establish cause-and-effect relationships. - Selection bias: Patients may not be representative of the entire population. - Confounding factors: Other factors could influence the observed outcomes. 3. Cross sectional study It looks at a population at a single point in time, like taking a slice or cross-section of a group, and variables are recorded for each participant. Main objective is to determine the prevalence such as assessing frequency of a disease Often useful when looking for an ethical approach to investigate harmful situations that would otherwise be unethical if inflicted on a participant Advantages: Limitations: -Efficient -Can not establish causation -Descriptive -Time-bound -Hypothesis generation -Prevalence bias -Large sample size -Rare diseases and conditions can be hard to investigate using a cross-sectional study design 4. Cohort study It’s an observational and analytical study. In these studies, the investigator did not assign exposures, a comparison group was used, and the exposure was the starting point for the research. The incidence of disease in the exposed group is compared with the incidence of disease in the unexposed group. Advantages: - the only observational study design that directly Limitations: investigates risk of disease and the factors - Not appropriate for rare diseases or those that take a contributing to it. long time to develop e.g. mesothelioma. - Ethically safe. - Not appropriate for studying multiple exposures. - Multiple outcomes can be measured. - Can be costly and time consuming. - They are good for rare types of exposures, e.g. an exposure to a chemical spill in a factory. 4. Cohort study The two groups of cohorts (exposed and un-exposed) are followed prospectively over time to track the development of new disease. Prospective Example: In a prospective cohort study researchers compared four different groups of women (two at-risk groups, two low-risk groups) to investigate which groups were more likely to develop PTSD symptoms after a birthing event. Cohorts are defined from a previous point in time, and are not followed up in the future. Information or data is collected from past clinical records and the outcome of interest is investigated. Retrospective Useful for tracking the progress of a disease with a long latency period. Example: In a retrospective cohort study researchers used previously collected data to investigate whether there was an association between birth experience and subsequent maternal care-giving attitudes and behavior over a 12-month period  5. Case control study In this study there are two groups of people: one has a health issue (Case group), and this group is “matched” to a Control group without the health issue based on characteristics like age, gender, occupation these studies estimate the odds between the exposure and the health outcome, however they cannot prove causality. Case-Control studies might also be referred to as retrospective or case-referent studies. Advantages: Limitations: - Helps you find the source of an existing illness or - Patient recall about their history can be inaccurate (recall epidemic. bias). - Cheap and quick to conduct this type of study. - Patients aware of certain risk factors may focus on those - The health issue has already occurred, you don’t and ignore other exposures. need a lab or special equipment. - No randomization is possible, lowering internal validity of - Few ethics issues as the patient already has the the study. health condition - Finding a Control group that matches the Case group - Looks at multiple risk factors in a patient’s life appropriately can be difficult. (environment, work, diet). - This study type does not prove a clear causal relationship between risk factors and illness, only calculates the odds. Thank you