Introduction to Research Methods Flashcards
Evidence based dentistry is …
the practice of dentistry that integrates the best available evidence with clinical experience and patient preference in making clinical decisions
Types of Study Design
- meta-analysis
- systematic review
- randomised control trial
- cohort
- case-control
- case series
- case report
- cross sectional
- narrative review
- ecological
Evidence Levels
Level 1 (most reliable)
> systematic review
> randomised control trial
Level 2
> cohort
Level 3
> case control
Level 4
> case series
> case reports
Level 5 (least reliable)
> narrative review
> editorial
> expert opinion
2 main types of epidemiological studies
1) descriptive
> no attempt made to understand why the data is the way it is, only describes the the findings e.g., that cancer rates are higher in Scotland than England
> examples include case reports, case series, cross-sectional/survey
2) analytical
> attempting to understand the data e.g., the cause of something such as why cancer levels are higher in Scotland than England (observational studies such as case-control or cohort; experimental studies such as randomised control trials)
Types of descriptive epidemiological studies
> all descriptive epidemiological studies are observational
> observational descriptive epidemiological studies can be either: case reports, case series, or cross-sectional/surveys
Types of analytical epidemiological studies
> analytical epidemiological studies can be either observational OR experimental
> observational analytical studies include: case control, or cohort
> experimental analytical studies include: randomised clinical trials
Features of Experimental Studies e.g., RCTs
> sample population chosen
sample divided into 2 groups
one group receives the intervention
one group receives the control/placebo
both groups are studied to assess an outcome
e.g., one group uses cylindrical shaped interdental brushes - one group uses conical shaped interdental brushes - both groups assessed for efficacy of plaque removal
Features of observational studies
> no intervention is given to participants
2 groups of participants
group 1 is of interest
group 2 is of comparison to the group of interest
both groups are followed over time
the outcomes of both groups are compared
e.g., group of smokers and non-smokers followed over time to determine if smoking is associated with lung cancer
Features of Cohort (longitudinal/follow-up) study design
- observational (i.e., no intervention given)
- follows a group of individuals (called a cohort) over time to investigate the relationship between an exposure/risk factor and a particular outcome/health condition
- cohorts are divided into 2 groups e.g., smoker and non-smoker
- can be prospective or retrospective
- prospective types recruit a group of individuals who do not have a particular disease or outcome of interest at the start of the study and then follow them over time to discover if the disease or outcome of interest develops
- retrospective types recruit a group of individuals who already have been exposed to the something and look back to see if they developed the disease or outcome of interest
- established intervals for follow-up and evaluating subjects within a defined interval, such as yearly or every 3 months
- needs to retain a high number of its participants over a long period of time
ADVANTAGES
> helpful in determining patterns i.e., cause and effect relationships
> more data is collected over longer periods of time allowing for better and more concise results
> cheaper than an experimental design
> high in validity
DISADVANTAGES
> expensive
> time consuming
> selection bias
> attrition bias as participants drop out or are lost so results not always generalisable to the whole population
Features of Case Report study design
- provides a detailed description of a patients medical history, diagnosis, treatment and outcome
- viewed only as hypothesis generating, such as calling attention to a new or unexpected clinical finding
- there are no controls, so any descriptions of therapeutic outcomes must be viewed cautiously
- clinical data are usually gathered from past clinical records
ADVANTAGES
> describes rare or poorly understood diseases or conditions
> helpful to generate hypotheses
> helpful to identify patterns or trends in patient populations
> conducted quickly and at low cost
DISADVANTAGES
> selection bias as patients reported may not represent the general population
> lack control group making it difficult to ascertain the effectiveness of different treatments or interventions
> descriptive as cannot establish causality
> cannot control for confounding factors
Features of Case-Series study design
- involves a group of patients sharing a similar disease or condition
- involves a comprehensive review of medical records for each patient to identify common features or disease patterns
- helps to better understand a disease’s presentation, diagnosis and treatment
- provides a broader perspective on a specific disease
ADVANTAGES
> describes rare or poorly understood diseases or conditions
> helpful to generate hypotheses
> helpful to identify patterns or trends in patient populations
> conducted quickly and at low cost
DISADVANTAGES
> selection bias as patients reported may not represent the general population
> lack control group making it difficult to ascertain the effectiveness of different treatments or interventions
> descriptive as cannot establish causality
> cannot control for confounding factors
Features of Cross-Sectional/Survey study design
- aims to classify participants into two distinct categories i.e., with disease or without disease
- aims to measure the prevalence or frequency of a disease in a population at a specific point in time
- the disease of interest or exposure has already occurred i.e., retrospective
- useful in determining the prevalence of more common diseases in the population of interest
- indirectly assess the value of public health measures such as water fluoridation, human papilloma virus (HPV) vaccination, or smoking cessation programs on disease prevalence
- must not infer causality from these studies
- The best cross-sectional studies evaluate outcomes using standardised methods and/or validated instruments
ADVANTAGES
> quick and inexpensive
> provides a snapshot of prevalence and distribution of a particular health condition in a population
> helps to identify patterns and associations
> helps to generate hypotheses for future research
DISADVANTAGES
> cannot establish causality
> selection bias as sample may not represent population
> cannot account for confounding variables
Features of the Case-Control study design (OBSERVATION
- no intervention given
- compares people who have developed a disease of interest (case) with people who have not developed the disease (control)
- helps to identify potential risk factors associated with the disease e.g., age, sex, lifestyle, environment (used to determine whether exposure to something might be related to the development/prevention of a certain disease)
- compares the prevalence of risk factors between the cases and controls to determine the association between them and the disease
- retrospective
DESIRABLE FEATURES
> at least the same number of controls as cases
> cases and controls must be evaluated using the same methods
> cases and controls should come from the same populations
> those judging clinical outcomes should not know whether a subject is a case or control
EXAMPLE
comparing patients with lung cancer to those without lung cancer to assess if smoking is a risk factor in the development of lung cancer
ADVANTAGES
> useful for studying rare diseases
> useful for investigating potential risk factors
> helpful when it is not ethical or practical to expose patients to variables or randomise participants
DISADVANTAGES
> selection bias
> cannot establish causality
> can be difficult recruiting suitable controls with similar characteristics to cases
Features of Clinical Trial study design (including randomised control trials)
- study that is testing an intervention which is anything that can alter the course of a disease, such as a pharmaceutical agent, a medical device, a surgical technique, a behavioural intervention, or a public health program
- randomised controlled trials provide the strongest evidence for the causal nature of a modifiable factor and a disease outcome (randomly allocates subjects to a placebo arm or active therapy arm; the randomisation procedure presumably controls for hidden factors that could influence outcomes)
- treatment assignment is concealed from the subjects enrolled in the study, the investigators conducting the study, and those conducting the statistical analyses until the final results are determined
- a phase I trials are used to establish dose and safety of a drug or intervention
- phase II trials are conducted to determine initial efficacy of a new intervention
- phase III trials are necessary to establish the efficacy of an agent and are sometimes referred to as pivotal trials because they enrol hundreds to thousands of subjects with diversity
- phase IV trials determine how well an efficacious treatment works in practice i.e., determine the effectiveness of a therapy
ADVANTAGES
> reliable study design for establishing causal relationships
> reduce the risk of selection bias
> controls confounding variables
DISADVANTAGES
> ethical concerns if an intervention is withheld from a group of people when it is known that the intervention is effective
> expensive
> time consuming
> have strict inclusion and exclusion criteria which limits generalisability to broader populations
