W6-L6 (DSA 458) Case Series, Cross-sectional and Correlational Studies (28.09.2023) PDF

Research Methodology (DSA 4580) Step 2: Selecting a Study Approach Case Series, Cross-sectional and Correlational Studies Academic Year: 2023-2024 Fifth Year DSA 4580 WEEK 6 LECTURE 6 Abdulhamid Al Ghwainem, BDS, MSc, DClinDent Pediatric Dentistry Assistant Professor in Pediatric Dentistry a.algh...

Research Methodology (DSA 4580) Step 2: Selecting a Study Approach Case Series, Cross-sectional and Correlational Studies Academic Year: 2023-2024 Fifth Year DSA 4580 WEEK 6 LECTURE 6 Abdulhamid Al Ghwainem, BDS, MSc, DClinDent Pediatric Dentistry Assistant Professor in Pediatric Dentistry [email protected] Thursday, 28 September 2023 Copyright © 2023 by PSAU, Abdulhamid Al Ghwainem Disclaimer DISCLAIMER The information presented in this lecture is offered for educational and informational purposes and should not be construed as medical, dental, or research advice. While the amount of information in this handout is vast, and I make every effort to be as current and thorough as possible, the information cannot be taken as a reference manual or textbook. Please note that you should read the required textbooks as specified in the course curriculum and lecture references. 2 Notice WARNING Materials used in connection with this course or lecture may be subject to copyright protection. 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Do not remove this notice 3 Outline § Research approaches and designs and its importance. § Classifications of research designs. § How to choose a research design. § Case report and case series. § Cross-sectional studies. § Correlational studies 4 Lecture Objectives By the end of this session, you should be able to: § Classify and differentiate between different research approaches and designs. § Identify and relate different studies approaches and designs for health research . § Select most appropriate research approaches and designs. § Define case report and case series and highlight their importance, key features, advantages and disadvantages. § Define cross-sectional study design and highlight its importance, key features, advantages and disadvantages. § Differentiate between prevalence and incidence. § Define correlational study design and highlight its importance, key features, advantages and disadvantages. 5 Research Process/Steps Research: answering questions in logical and systematic ways Question Answer Research methodology: how to get from Question to Answer 6 Research Process/Steps Research: answering questions in logical and systematic ways Question Answer Research methodology: how to get from Question to Answer Identify study question Select study approach Design study and collect data 7 Analyse data Report findings Research Process/Steps Research: answering questions in logical and systematic ways Identify study question Select study approach Design study and collect data 8 Analyse data Report findings Research Process/Steps Step 2: Selecting a Study Approach 9 Research Approaches and Designs § Study design refers to the methods and methodologies used in research to gather the data needed to explore a specific question. § Some research questions are best approached by statistical analysis of data. This is quantitative research. § Others are better answered by looking for patterns, features or themes in the data. This is qualitative research. Illustrates how research methodology and research method relate to each other. Source: Andiappan and Wan (2020) 10 Research Approaches and Designs Why do you need to understand study designs? § Unreliable research can still be published even with peer-review processes. § Effective evaluation of research involves assessing the way a study has been designed and conducted. § This helps you determine how valid the research is for your own study or practice. § Being able to identify and understand different study designs means you can spot the signposts of a good or flawed study. § Essentially you are using your critical thinking to evaluate evidence, which you need to do in assessments like literature reviews. 11 Research Approaches and Designs Study designs in medical research have similar components (as we’d expect from the PICO): • A defined population (P) from which groups of subjects are studied • Outcomes (O) that are measured And for experimental and analytic observational studies: • Interventions (I) or exposures (E) that are applied to different groups of subjects 12 Research Approaches and Designs A series of questions can help identify the most suitable approach: § Do new data need to be collected, or are there existing data sources that can be used to answer the study question? § If new data will be collected, is an experimental study required or can the study question be answered using non-experimental methods? § Is the research question based primarily on exposure status, disease status, or membership in a particular population? § Are there time constraints? 13 Research Approaches and Designs Algorithm for classifying the types of research, this scheme is intended to classify the study types as clearly as possible. Medical Research Primary Research Epidemiological Research Basic Research Theoretical § § § § Method development § (physics, chemistry § biology, § bioinformatics) § Analytical § measurement procedure Imaging procedure Test development assessment procedure Weaker evidence Secondary Research Applied Cell research Animal research Stem cell research Genetics Tissue banking Clinical Research Descriptive Case Report A report on a single patient with an outcome of interest Case Series A report on a series of patients with an outcome of interest. No control group is involved Analytical Surveillance Study Report obtained from the databases that follow and record a health problem for a certain time Qualitative Ecological Cross-sectional Examines the relationship between exposure and outcome by examining population-level data rather than individuallevel data 14 Exposure and Exposure ← Outcome outcome are at the same time Meta-analysis QuasiExperimental Research Randomised Controlled Trial Case-control Systematic Review Cohort Exposure → Outcome Stronger evidence Research Approaches and Designs The type of study can generally be worked at by looking at many issues: § Is it a primary research (collecting new data) or a secondary research (synthesizing already published research)? § Is it a basic research (e.g.: laboratory research) or clinical research (e.g.: involving human subjects)? § What is the research question or the aim of the study? 1.To simply describe a population (PO questions) descriptive 2.To quantify the relationship between factors (PICO questions) analytic. 15 Research Approaches and Designs The type of study can generally be worked at by looking at many issues: § Is there an intervention or experimental group? 1. Yes? RCT 2. No? Observational study For observational study, the main types will then depend on the timing of the measurement of outcome. § Is there a comparison or control group? 1. Yes? Analytical study 2. No? Descriptive study 16 Research Approaches and Designs The type of study can generally be worked at by looking at many issues: § When were the outcomes determined? 1.Sometime after the exposure or intervention? cohort study (‘prospective study’) 2.At the same time as the exposure or intervention? cross sectional study or survey 3.Before the exposure was determined? case-control study (‘retrospective study’ based on recall of the exposure) 17 Putting all this together 18 Research Approaches and Designs Study Designs Decision Tree is not completely exhaustive but covers most basics designs All Types Of Research Designs And Approaches Secondary Research All Types of Reviews Systematic Review Metaanalysis Is it a primary research (collecting new data) or a secondary research (synthesizing already published research)? Primary Research Basic Is it a basic research (e.g.: laboratory research) or clinical research (e.g.: involving human subjects)? Clinical Is there an intervention or experimental group? Yes Yes No Analytical Study Is there a comparison or Interventional/Experi Observational Study mental Study control group? No What is the starting point for research? Randomised Controlled Trial Non-randomised Controlled Trial Descriptive Study Exposure and Outcome at the same time Survey (Crosssectional) Outcome Exposure Case-control Study Cohort Study Case Report Case Series Analytical Crosssectional Study Qualitative Study Based on the work of Grimes et al., (2002). Grimes, D. A., & Schulz, K. F. (2002). “An overview of clinical research: The lay of the land”. The Lancet, 359(9300), 57-61 19 Research Approaches and Designs These eight common study designs used for health research were highlighted in previous lectures 20 Hierarchy of Evidence: This Photo by Unknown Author is licensed under CC BY 21 Case Report and Case Series: overview A case study, also known as a case report, is an in depth or intensive study of a single individual or specific group, while a case series is a grouping of similar case studies/case reports together. A case study/case report or case series can be used in the following instances: § Where there is atypical or abnormal behaviour or development § An unexplained outcome to treatment § An emerging disease or condition § Adverse reactions to treatments 22 Case Report and Case Series: overview § Case Report: a in depth or intensive report of the symptoms, signs, diagnosis, treatment, and follow-up of an individual patient Hospital/Clinical notes/records Journal Article § Case Series: a description of the characteristics and outcomes among a series of individuals with either a disease or an exposure (no control group) Journal Article Hospital/Clinical notes/records 23 Case Report and Case Series: overview Key Features Of Case Report and Case Series Aim/Objective Describe a case/a group of individual with a disease or exposure of interest Research Question What are the characteristics of the included case/cases? Case/Sample/Population Individual/all Individual MUST have the same disease or exposure or have undergone the same procedure When you use this design A source of included case/cases is available, and when there is no comparison or control group Requirement/Resources An appropriate source of cases (e.g.: clinical notes, records) Steps 1. 2. 3. 4. What to look for A lack of generalizability Key statistical measure Only descriptive statistics are required Specify what new and important information the study will provide Identify a source of case/cases Define and assign a case definition Select the characteristic of the study case/cases that will be described 24 Advantages and Disadvantages of Case Report and Case Series § Advantages: § Disadvantages: • One case to raise an attention • May include researcher bias (selection bias). • No control (uncontrolled). • Difficult to replicate. • Difficult to compare different cases. • Can't always be generalised to the general population. • Unknown future outcome/follow up. • Can be published quickly. • Educational. • Observational. • Identify rare conditions. • Provides very detailed information. • Allows detailed investigation into situations which would be unethical or impractical to perform using another study design 25 Case Report and Case Series: overview Which clinical questions does Case Study/Case Report/Case Series best answer? § Unreported or unusual side effects or adverse interactions involving medications. § Unexpected or unusual presentations of a disease. § New associations or variations in disease processes. § Presentations, diagnoses and/or management of new and emerging diseases. § An unexpected association between diseases or symptoms. § An unexpected event in the course of observing or treating a patient. § Findings that shed new light on the possible pathogenesis of a disease or an adverse effect 26 Case Report and Case Series: overview § Case definition: a list of the inclusion and exclusion criteria that must be met for an individual to be classified as a person with the disease of interest in a case series, a case–control study, or another type of study § The first step in defining a case definition is clarifying what constitutes the disease or disorder of interest –Sign: an objective indication of disease that can be clinically observed, such as a rash, cough, fever, or elevated blood pressure –Symptom: a subjective indication of illness that is experienced by an individual but cannot be directly observed by others 27 Case Report and Case Series: data collection After defining the disease or procedure of interest, then other important step in establishing a case definition is selecting the relevant PPTs, the person, place, and time characteristics üThe characteristics of the population (person) üThe place where the person lived, worked etc (place) üThe date when the disease or death occurred (time) 28 Case Report and Case Series: data collection § Case report or case series might be constructed from primary data acquired by interviewing cases about their experiences using a questionnaire and/or qualitative techniques § When medical records will be consulted as part of the data collection process, it is often helpful to create a questionnaire that guides the extraction of data from these files 29 Case Report and Case Series: ethics § Researchers conducting case report or case series studies must be extremely careful about protecting patient privacy and confidentiality. § Consent? § Ethical approval? 30 Case Report and Case Series: analysis § Most case study reports do not require any numbers beyond simple counts and percentages § Statistical tests may be used to compare subpopulations of cases or to compare before-and-after measures for the same individual participants when the sample size is sufficiently large 31 Case Report and Case Series: analysis § Case fatality rate (CFR): the proportion of people with a particular disease who die as a result of that condition § Mortality rate: the percentage of members of a population who die from any condition (an all-cause mortality rate) or from a particular condition (a causespecific mortality rate) during a specified time period § Proportionate mortality rate (PMR): the proportion of deaths in a population during a particular time period that were attributable to a particular cause 32 Critical Appraisal Tools and Checklists of Case Report and Case Series: § Joanna Briggs Institute (JBI checklist): https://jbi.global/critical-appraisal-tools § The Center for Evidence-Based Management (CEBMa checklist): https://cebma.org/resources-and-tools/what-is-critical-appraisal/ 33 Critical Appraisal Tools and Checklists of Case Report and Case Series: • Factors to look for: § Selected condition measured in a standard and reliable way § Inclusion and exclusion criteria § Confounding § Data collection § Appropriate statistical analysis § Presentation of results (clear, precise) § Applicability to local and general population 34 Case Report and Case Series: examples Primera, G., Matta, J., Eubank, L., & Gurung, P. (2023). The Lost Crown: A Case of an Aspirated Tooth Crown Causing PostObstructive Pneumonia. Case reports in dentistry, 2023, 4863886. https://doi.org/10.1155/2023/4863886 Koruyucu, M., Bayram, M., Tuna, E. B., Gencay, K., & Seymen, F. (2014). Clinical findings and long-term managements of patients with amelogenesis imperfecta. European journal of dentistry, 8(4), 546–552. https://doi.org/10.4103/1305-7456.143640 35 Break Out Session Instructions: Scan the following QR codes: • Identify and explain the design of the research • What are the journals? • Who are the corresponding authors? • What are the general outline of these types of study design? 36 Break Out Session Feedback 37 Cross-Sectional Studies: overview § A cross-sectional study provides information about a health condition/disease that exists at a given time. § A cross-sectional study is an observational study. § Often described as a “snapshot” of a population in a certain point in time because exposure and outcome are determined simultaneously for each subject. § Cross-sectional is also called prevalence study or surveys. 38 Cross-Sectional Studies: overview § Cross-sectional Study: the observation of a defined population at a single point in time or time interval. Exposure and outcome are determined simultaneously. Gold standardin diagnosis and screening research Present Future Pro- Population Can compare groups within one sample Sample Past Retro- Data collected at one time point on one representative sample Direction of time Starting point in time 39 Cross-Sectional Studies: overview § It can be descriptive and analytical § Descriptive cross-sectional study only describes the number of cases or events in a particular population at a time point or during a period of time; § Analytic cross-sectional study can be used to infer relationships between a disease and other variables. § Cross-sectional studies can be helpful in determining how many people are affected by a condition and whether the frequency of the occurrence varies across groups or population characteristics. 40 Cross-Sectional Studies: overview § In a hypothetical example of a cross-sectional study, we can record the prevalence of periodontal disease and investigate the association between periodontal disease and oral hygiene habits in adult patients. § The outcome is the presence or absence of periodontal disease § The exposure is current oral hygiene practices such as frequency of brushing and use of dental floss § This study can be carried out by surveying/interviewing participants about their oral hygiene habits and at the same time by assessing periodontal status clinically. § Thus, outcomes and exposure data are assessed at the same time. 41 Cross-Sectional Studies: overview • Repeated cross-sectional study: a series of cross-sectional studies that resample and re-survey representatives from the same source population at two or more different time points – A repeated cross-sectional study design does not track the same individuals forward in time – A new set of participants is sampled from the source population for each round of data collection 1 2.. 42 Cross-Sectional Studies: overview Cross-sectional studies can be used in the following instances: § Describe a population or a subgroup within the population with respect to an outcome and a set of risk factors. § Find the prevalence of the outcome of interest, for the population or subgroups within the population at a given time point. § Appropriate for screening hypotheses because they require relatively shorter time and fewer resources. § Find associations between risk factors and the outcome of interest. However: § They are limited in confirming causality. § They are prone to selection and information bias and confounding. 43 Cross-Sectional Study: overview Key Features Of Cross-Sectional Studies Aim/Objective Describe the exposure and/or disease status of a population/sample Research Question What is the prevalence of the exposure and/or disease in the population/sample? Case/Sample/Population The study participants MUST be representative of the source population When you use this design Time is limited and/or the budget is small Requirement/Resources The exposure and outcomes are relatively common, and the researcher expect to be able to recruit several hundred participants Steps 1. Define a source population 2. Develop a strategy for recruiting a representative sample 3. Decide on the methods to be used for data collection What to look for Non-representative sample Key statistical measure Mainly descriptive statistics are required, to determine the prevalence 44 Advantages and Disadvantages of Cross-Sectional Studies § Disadvantages: § Advantages: • Cannot tell us about causal relationships (only correlation , no cause and effect). • Generalizability limited by sampled population and population definition. • Sample size requirements may be very large (especially when looking at rare outcomes or exposures). • Not suitable for studying rare diseases, since very few subjects will be captured in the study, even if it includes a big number of participants. • Potential for selection bias information bias, and confounding. • It evaluates prevalence rather than incidence. • Relatively inexpensive and fast to conduct. • Can estimate prevalence of outcome of interest because sample is usually taken from the whole population. • Many outcomes and risk factors can be assessed. • Useful for public health planning, understanding disease aetiology and for the generation of hypotheses. • No loss to follow-up. 45 Cross-Sectional Studies: surveys § Survey: the gathering of data from individuals using a list of questions § KAP survey: a survey instrument that asks participants about their knowledge, attitudes (or beliefs or perceptions), and practices (or behaviors) 46 Cross-Sectional Studies: surveillance § Surveillance: the process of continually monitoring health events in a population so that emerging public health threats can be detected, and appropriate control measures can be implemented quickly – Active surveillance: the process of public health officials contacting healthcare providers in their jurisdictions to ask how often the clinicians are diagnosing particular types of disease – Passive surveillance: the compilation of reports of notifiable disease diagnoses submitted by medical laboratories 47 Cross-Sectional Studies: sampling § The participants in a cross-sectional study must be reasonably representative of one well-defined population § Representativeness: the degree to which the participants in a study are similar to the source population from which they were drawn § For instance, in a study assessing the prevalence of dental caries among Saudi population, the sample should include a random sample of all Saudi population; otherwise, the results will not be valid because of selection bias 48 Cross-Sectional Studies: prevalence § Prevalence is a useful measure of the burden of disease. Knowing about the prevalence of a specific disease can help us to understand the demands on health services to manage this disease. § Prevalence changes when people with the condition are cured or die. Bear in mind that increased prevalence doesn’t necessarily mean a bigger problem. Higher prevalence could mean a prolonged survival without cure or an increase of new cases, or both. A lower prevalence could mean that more people are dying rather than being cured, a rapid recovery, and/or a low number of new cases. § Prevalence = the number of cases of a disease in a specific population at a particular timepoint or over a specified period of time. § When we talk about prevalence, we can either refer to ‘point prevalence’ or ‘period prevalence’. 49 Cross-Sectional Studies: prevalence § Point prevalence is the proportion of people with a particular disease at one point in time and can be calculated as follows: § Period prevalence is the proportion of people with a particular disease during during a defined time period, such as several weeks or several months. § Prevalence ratio (PR): a comparison of the prevalence of a characteristic in two independent populations (or independent subpopulations) that is calculated by taking a ratio of their prevalence rates § Because a cross-sectional study has no time dimension, it cannot be used to assess causality – An exposure can be said to be “associated” or “related” to a disease, but a cross-sectional study cannot show that an exposure caused a disease 50 Cross-Sectional Studies: incidence § Incidence = the rate of new cases of a disease occurring in a specific population over a particular period of time. § Two types of incidence are commonly used: ‘incidence proportion’ and ‘incidence rate’. § Incidence proportion, risk or cumulative incidence refers to the number of new cases in your population during a specified time period. It can be calculated using the following equation: § Incidence rate incorporates time directly into the denominator and can be calculated as follows: Person years at risk means the total amount of time (in years) that each person of the study population is at risk of the disease 51 during the period of interest. Cross-Sectional Studies: prevalence vs incidence § Prevalence differs from incidence proportion as prevalence includes all cases (new and pre-existing cases) in the population at the specified time whereas incidence is limited to new cases only. § The factor connecting prevalence and incidence statistics is the length of time the disease is present for before patients die or are cured. For example…? 52 The Sources of Bias in Cross-Sectional Studies Bias can be introduced because of any systematic errors in the design, conduct, or analysis of research 1. Selection Bias: occurs when individuals or groups in a study differ systematically from the population of interest leading to a systematic error in an association or outcome § Sampling bias: representativeness, when sampling from the study population, ideally random sampling should be implemented because it gives the same probability for each person to be included in the study and thus ensures that the drawn sample represents the study population § Prevalence-incidence bias (Neyman bias): It arises when a gap in time occurs between exposure and selection of study subjects § Response and non-response bias: occurs due to systematic differences between responders and non-responders 53 The Sources of Bias in Cross-Sectional Studies Bias can be introduced because of any systematic errors in the design, conduct, or analysis of research 2. Information Bias: arises from systematic differences in the collection, recall, recording or handling of information used in a study. 3. Measurement Bias: occurs when information collected is inaccurate. 4. Confounding: A situation in which the effect or association between an exposure and outcome is distorted by the presence of another variable which can confuse the association between an exposure and an outcome. 54 Critical Appraisal Tools and Checklists of Cross-Sectional Stuies: § STrengthening the Reporting of OBservational studies in Epidemiology ( STROBE Checklist): checklist of 22 items https://www.strobe-statement.org/checklists/ § Joanna Briggs Institute (JBI checklist): checklist of 8 items https://jbi.global/critical-appraisal-tools § The Center for Evidence-Based Management (CEBMa checklist): checklist of 12 items https://cebma.org/resources-and-tools/what-is-critical-appraisal/ § Appraisal tool for Cross-Sectional Studies (AXIS): checklist of 20 items https://bmjopen.bmj.com/content/bmjopen/6/12/e011458/DC2/embed/inline-supplementary-material-2.pdf?download=true § The National Institutes of Health (NIH quality assessment tool): 14 items https://www.nhlbi.nih.gov/health-topics/study-quality-assessment-tools § Specialist Unit for Review Evidence (SURE): checklist of 12 items https://www.cardiff.ac.uk/__data/assets/pdf_file/0010/1142974/SURE-CA-form-for-Cross-sectional_2018.pdf 55 Critical Appraisal Tools and Checklists of Cross-Sectional Stuies: • Factors to look for: § Population, sampling technique, sample selection and size , power calculation § Inclusion and exclusion criteria § Response rate § Non-responders § Confounding § Measurement Validity & Reliability § Appropriate statistical analysis § Presentation of results (clear, precise) § Applicability to local and general population 56 Case Report and Case Series: examples Sulimany, A. M., Alsamhan, A., Alawwad, A. A., Aqueel, M., Alzaid, N., Bawazir, O. A., & Hamdan, H. M. (2021). Knowledge Levels and Educational Experiences among Dental Graduates in Saudi Arabia Regarding Child Abuse and Neglect: A National Study. Children (Basel, Switzerland), 8(9), 724. https://doi.org/10.3390/children8090724 Al-Majed, I., Murray, J. J., & Maguire, A. (2001). Prevalence of dental trauma in 5-6- and 12-14-year-old boys in Riyadh, Saudi Arabia. Dental traumatology : official publication of International Association for Dental Traumatology, 17(4), 153–158. https://doi.org/10.1034/j.1600-9657.2001.170403.x 57 Break Out Session Instructions: Scan the following QR code: • Identify and explain the design of the research • What are the population, sampling technique, and inclusion and exclusion criteria? • What are the main findings? 58 Break Out Session Feedback 59 Correlational/Ecological Studies: overview § A correlational study uses population-level data to look for associations between two or more characteristics that have been measured in several groups § The variables included in correlational analyses are usually aggregate (grouped) statistics such as the proportion of a population with a particular characteristic or the average value of the variable in a population § A correlational study is sometimes called an aggregate study because correlational studies look only at grouped population-level data and they do not include any individual-level data 60 Correlational/Ecological Studies: overview § For most correlational studies, at least one characteristic of the populations being examined is designated as an exposure and at least one is designated as an outcome or disease § Correlational studies then examine exposure–outcome pairs –Statistical methods can be used to control for interactions among related variables § A correlational study that explores an environmental exposure may be called an ecological study 61 Correlational/Ecological Studies: overview § Correlational studies compare groups rather than individuals – No individual-level data are included in the analysis, only population-level data § Ecological fallacy: the incorrect assumption that individuals follow the trends observed in population-level data – The experience of individuals in a population may vary significantly from the population average 62 Correlational/Ecological Studies: overview § Information about all the variables of interest must be available for a suitable number of populations, which can be grouped by place or time – For any one variable in a correlational study, the best option is for all data to come from the same source – When using multiple sources of data for one variable, the researcher should establish a scientifically justifiable set of inclusion criteria for the study and then exclude any data sources that do not meet all of those eligibility requirements 63 Correlational/Ecological Studies: overview Key Features Of Correlational Studies Aim/Objective Compare average level of exposure and outcome in several populations Research Question Do populations with a higher rate of exposure half a higher rate of disease? Case/Sample/Population Existing population-level data are used: there are no individual participants When you use this design To explore possible association between exposure and the disease using population-level data Requirement/Resources The topic has not been previously explored using individual-level data Steps 1. Select the sources of data that will be used 2. Decide on the variables to include in the analysis What to look for The ecological fallacy, limited publication Key statistical measure Mainly descriptive statistics are required, to determine the correlation 64 Advantages and Disadvantages of Correlational Studies § Advantages: § Disadvantages: • Collect much information from many subjects at one time. • Cannot tell us about causal relationships (only correlation, no cause and effect). • Interpretation of results is difficult. • Study a wide range of variables and their interrelation. • Show strength of relationship between two variables. • Gain quantitative data which be easily analysed. 65 Correlational/Ecological Studies: data collection Before conducting a statistical analysis of aggregate data, the data from each population must be entered into a spreadsheet • Each population should be assigned to its own row in the spreadsheet • Each exposure and each outcome should be assigned to its own column • The data should be filled into the cells in each column so that they line up with the correct population 66 Correlational/Ecological Studies: analysis § When all the points fall neatly along or very near to a sloped line (with a positive upward or negative downward slope), the correlation is strong § When the points are not exactly linear but a line for trend can be drawn through them, the correlation is mild or moderate § When the points appear to be randomly placed and no obvious line can be drawn through them, or when the best-fit line is horizontal then the correlation is weak or nonexistent 67 Correlational/Ecological Studies: analysis • Different equations are used to calculate correlations between different types of variables – The Pearson correlation coefficient (r) is used for continuous variables and other variables with responses that can be plotted on a number line (such as age) – The Spearman rank-order correlation (ρ = rho) is used with variables that assign a rank to responses (like 1st place, 2nd place, 3rd place, and so on) or that have ordered categories (such as scales that range from 1 = strongly disagree to 5 = strongly agree) 68 Correlational/Ecological Studies: analysis • The value of r (or ρ) ranges from –1, when all points lie perfectly on a line with a negative slope, to 1, when all points lie perfectly on a line with a positive slope – When r = 0, there is no association between the exposure and outcome • The coefficient of determination, r2, shows how strong a correlation is without indicating the direction of the association – The value of r2 ranges from 0 for no correlation to 1 for perfect correlation 69 Correlational/Ecological Studies: example Aida, J., Ando, Y., Aoyama, H., Tango, T., & Morita, M. (2006). An ecological study on the association of public dental health activities and sociodemographic characteristics with caries prevalence in Japanese 3-year-old children. Caries research, 40(6), 466–472. https://doi.org/10.1159/000095644 70 Putting all this together 71 Research Approaches and Designs Algorithm for classifying the types of research, this scheme is intended to classify the study types as clearly as possible. Medical Research Primary Research Epidemiological Research Basic Research Theoretical § § § § Method development § (physics, chemistry § biology, § bioinformatics) § Analytical § measurement procedure Imaging procedure Test development assessment procedure Weaker evidence Secondary Research Applied Cell research Animal research Stem cell research Genetics Tissue banking Clinical Research Descriptive Case Report A report on a single patient with an outcome of interest Case Series A report on a series of patients with an outcome of interest. No control group is involved Analytical Surveillance Study Report obtained from the databases that follow and record a health problem for a certain time Qualitative Ecological Cross-sectional Examines the relationship between exposure and outcome by examining population-level data rather than individuallevel data 72 Exposure and Exposure ← Outcome outcome are at the same time Meta-analysis QuasiExperimental Research Randomised Controlled Trial Case-control Systematic Review Cohort Exposure → Outcome Stronger evidence Research Approaches and Designs Study Designs Decision Tree is not completely exhaustive but covers most basics designs All Types Of Research Designs And Approaches Secondary Research All Types of Reviews Systematic Review Metaanalysis Is it a primary research (collecting new data) or a secondary research (synthesizing already published research)? Primary Research Basic Is it a basic research (e.g.: laboratory research) or clinical research (e.g.: involving human subjects)? Clinical Is there an intervention or experimental group? Yes Yes No Analytical Study Is there a comparison or Interventional/Experi Observational Study mental Study control group? No What is the starting point for research? Randomised Controlled Trial Non-randomised Controlled Trial Descriptive Study Exposure and Outcome at the same time Survey (Crosssectional) Outcome Exposure Case-control Study Cohort Study Case Report Case Series Analytical Crosssectional Study Qualitative Study Based on the work of Grimes et al., (2002). Grimes, D. A., & Schulz, K. F. (2002). “An overview of clinical research: The lay of the land”. The Lancet, 359(9300), 57-61 73 Research Approaches and Designs Key Features Of Case Report and Case Series Key Features Of Cross-Sectional Studies Key Features Of Correlational Studies Aim/Objective Describe a case/a group of individual with a disease or exposure of interest Aim/Objective Describe the exposure and/or disease status of a population/sample Aim/Objective Compare average level of exposure and outcome in several populations Research Question What are the characteristics of the included case/cases? Research Question What is the prevalence of the exposure and/or disease in the population/sample? Research Question Do populations with a higher rate of exposure half a higher rate of disease? Case/Sample/P opulation Individual/all Individual MUST have the same disease or exposure or have undergone the same procedure Case/Sample/Po pulation The study participants MUST be representative of the source population Case/Sample/Popul ation Existing population-level data are used: there are no individual participants When you use this design A source of included case/cases is available, and when there is no comparison or control group When you use this design Time is limited and/or the budget is small When you use this design To explore possible association between exposure and the disease using population-level data Requirement/ Resources An appropriate source of cases (e.g.: clinical notes, records) Requirement/Re sources The exposure and outcomes are relatively common, and the researcher expect to be able to recruit several hundred participants Requirement/Reso urces The topic has not been previously explored using individual-level data Steps 1. Steps 1. 2. Steps 1. 2. What to look for The ecological fallacy, limited publication Key statistical measure Mainly descriptive statistics are required, to determine the correlation 2. 3. 4. Specify what new and important information the study will provide Identify a source of case/cases Define and assign a case definition Select the characteristic of the study case/cases that will be described What to look for A lack of generalizability Key statistical measure Only descriptive statistics are required 3. Define a source population Develop a strategy for recruiting a representative sample Decide on the methods to be used for data collection What to look for Non-representative sample Key statistical measure Mainly descriptive statistics are required, to determine the prevalence 74 Select the sources of data that will be used Decide on the variables to include in the analysis References Required: Neale, J., 2020. Research methods for health and social care. Bloomsbury Publishing. Jacobsen, K.H., 2020. Introduction to health research methods: A practical guide. Jones & Bartlett Publishers. Additional: Bowling, A., 2014. Research methods in health: Investigating health and health services. Maidenhead, United Kingdom: Open University Press. Creswell, J.W. and Creswell, J.D., 2018. Research design: Qualitative, quantitative, and mixed methods approaches. Sage publications. World Health Organization. Regional Office for the Western Pacific, 2001. Health research methodology : a guide for training in research methods. 2nd ed.. WHO Regional Office for the Western Pacific. https://apps.who.int/iris/handle/10665/206929 World Health Organization. Regional Office for the Eastern Mediterranean. (2004). A practical guide for health researchers. https://apps.who.int/iris/handle/10665/119703 References Cited references: § Andiappan, V., Wan, Y.K. Distinguishing approach, methodology, method, procedure and technique in process systems engineering. Clean Techn Environ Policy 22, 547–555 (2020). § Grimes, D. A., & Schulz, K. F. (2002). “An overview of clinical research: The lay of the land”. The Lancet, 359(9300), 57-61 Next Lecture: Step 2: Selecting a Study Approach Case-Control and Cohort Studies Identify study question Select study approach Design study and collect data Thank you! Any questions [email protected] Analyse data Report findings