The anatomy and physiology of clinical research part 2 Flashcards
Background significance
This section sets the proposed study into context and gives its rationale.
In published scientific articles, the “introduction” section is first read by many readers to tell them “where the article is going and why”.
This section cites previous research that is relevant and indicates the problems with the prior research and what uncertainties remains.
It will specify how the findings of the proposed protocol will help resolve these uncertainties and lead to new scientific knowledge.
Move structure 3 step process
Introduce a research area (general)
identify the gap
fill the gap (specific)
Study design
Whenever a study is being planned or designed, researcher cannot:
- Manipulate the independent variables.
- Examine the cause and effect between two variables.
HOWEVER, it is possible to examine the associations between the independent (predictor) and dependent (outcome) variables in a study.
Clinical Studies are observational studies that considers an association between two variables
The researcher does not manipulate the independent variable(s).
This is not to say that it is impossible to do so, but it will be impractical or unethical to do so. It is not possible to examine the cause and effect between the variables, but we can examine the associations or relationship between the predictor/independent and outcome/dependent variables
Association = connection
Observational studies
Considering an association between two variables
How study design is split
It is split into clinical trials and clinical studies
Clinical studies is split into cross sectional studies, cohort studies and case control studies
Clinical trials is split into phases 1,2,3,4
Cohort studies
For example, a researcher may be interested in the effect of illegal, recreational drug use (the independent variable(s)) on certain types of behavior (the dependent variable(s)). However, whilst possible, it would be unethical to ask individuals to take illegal drugs in order to study what effect this had on certain behaviors. As such, a researcher could ask both drug and non-drug users to complete a questionnaire that had been constructed to indicate the extent to which they exhibited certain behaviors
Predictor (independent variable) - the effects of illegal, recreational drug use
Outcome (dependent variable) - people with a certain type of behavior
It is unethical to ask the subjects to take the illegal drugs for the researchers to investigate the drugs’ effects on their behaviour especially those who are unwilling.
However, a researcher can create a questionnaire for both drug and non-drug users to fill in to indicate the extent to which they exhibit certain behaviours.
Case control study / retrospective study
Compares patients who have the disease or outcome of interest (cases) with patients who do not have the disease or outcome (control) from the same population.
Cases definition
cases - patients who already have the disease or outcome
control - patients who do not have the disease or outcome
The main objective is to determine the exposure to risk factor of interest from both the cases and control group
example of retrospective study:
There is a suspicion that ZnO found in sunscreens worn by lifeguards is more effective at preventing sunburns that lead to skin cancer than other sunscreens.
We want to investigate if sunscreen containing ZnO is a more effective in the prevention of skin cancers
cases - a group of former lifeguards that had developed cancer on their cheeks and noses was
compared to
control - a group of lifeguards without this type of cancer
the lifeguards were also assessed on their prior exposure to ZnO and other sunscreens without ZnO
Characteristics of Retrospective study
Want to look back at the history of each of the persons to compare how frequent they had been exposed to mentioned risk factor in order to determine the relationship between the risk factor and disease.
No intervention is attempted
No attempt is made to alter the course of the disease
Require the subjects to recall information which could be very difficult
Goal is to determine the exposure to the risk factor of interest from each of the two groups – cases and controls
The controls must match similarly to cases to ensure other variables do not affect the results
in this case, same age, similar number of seasons as life guard, amount of time per season etc.
Case control studies: Persistent pulmonary hypertension of the newborn (PPHN)
Persistent pulmonary hypertension of the newborn is associated with substantial infant mortality and morbidity
There might be an association between the PPHN disease and the use of selective serotonin reuptake inhibitor Fluoxetine late in the 3rd trimester of pregnancy.
Perform a case control study to assess whether PPHN is associated with exposure to SSRIs during late pregnancy
Case control studies
Studies are applied as investigators are looking at whether a suspected exposure contributed to the outcomes in patients
compare 2 groups of people, one with disease (cases), and another similar group of people who do not have the disease or condition (controls)
Cohort studies (may be retrospective and prospective)
One or more samples (usually a large number) are followed over time.
Determine if a participant’s exposure (risk factor) is associated with disease/outcome
Retrospective studies
Examine information and specimens that have been collected from the past
Prospective studies
Studies that begin in the present and follow subjects into the future
Subjects who develop the disease over time is recorded
Cross sectional studies/prevalence studies
Disease and exposure are measured simultaneously in a given population. This is also known as prevalence studies.
Provides a “SNAPSHOT” of the frequency and characteristics of a disease in a population at a particular point in time.
Measure the prevalence of exposure with prevalence of disease/outcome.
Cross Sectional Studies provide useful information for planning health services and results can usually be obtained quickly.
Advantages of cross sectional studies
These studies are easy to conduct and relatively cheap
– does not require follow up
Allow researchers to compare many different variables at the same time
Disadvantage of cross sectional studies
Not possible to determine the direction of the association, i.e. not known if the exposure preceded the disease and is therefore a potential cause of disease
example: cant tell whether having cats is linked to being poor or having no cats is linked to being rich
Aim to provide data on the entire population under study unlike case control studies which include individuals with a specific characteristics
Aim of cross sectional studies
Aim to provide data on the entire population under study unlike case control studies which include only individuals with a specific characteristic
Purpose of Clinical trials
Examine the EFFECT of an INTERVENTION & allows the investigator to observe the EFFECT(S) on the OUTCOME VARIABLE. Often appear at a very late stage of the study
2 main purposes
- Assessment of the efficacy and/ or safety of a drug/treatment
- Comparing the efficacy, safety, risk benefit, relationship or utility of 2 treatments
Cross sectional studies vs cohort studies vs case control studies
Cross-sectional studies only provides a snapshot of the frequency and characteristics of a disease in a population at a particular point of time.
Cohort studies follows a group of people through time (usually years) and record which individuals develop the outcome of interest.
If comparing the wheat consumption of children who have celiac disease and without celiac disease before their first birthday, case control studies are appropriate for this study.
example of cohort study, assess the impact of sun exposure to skin damage in dragon boaters.
Some team members applied sunscreens and some did not.
at the end of practice, the dragon boater skin was analyzed for texture, sun damage and burns
Comparison of skin damage were then made based on the use of sun screen
