1 - 3 - EPIDEMIOLOGY AND PUBLIC HEALTH IN DERMATOLOGY Flashcards
study of disease in the population, and it includes the incidence, prevalence, distribution, cause, and natural history of disease.
Epidemiology
interventional studies that include randomized controlled trials (RCTs
Clinical trials
evaluates how an individual receives health care and interacts with the health care system
Health services research
most commonly refers to studies of how patients interact with their health care and disease
Patient-oriented research
course of the disease from its onset until its, or the patient’s, end or resolution, the latter of which may be study outcomes of interest
natural history of disease
measure of how an individual is affected by an illness
burden of disease
observation of primary interest
outcome
the strongest association between a risk factor or intervention and an outcome
causal association
application of a substance or an action to subjects in an experimental study
intervention
attribute that increases the likelihood of developing a disease or other outcome of interest
risk factor
occurs when an attribute or other factor is found to be related to an outcome of interest
association
systematic error that causes the results of a study to deviate from the truth
Bias
systematic error in a study caused by how subjects are selected or not selected for a study
Selection bias
bias that occurs because of reporting
. Information bias i
occurs when two risk factors or exposures are associated with each other and the outcome of interest
Confounding
measure of an effect in an** ideal setting**
Efficacy
Studies that minimize bias are thought to be _______
**internally valid, **which means that if the study was repeated using the same study design and the same study cohort, the same results would be found
Studies that measure efficacy are called __________
explanatory studies
how well an intervention works in the real world
Effectiveness
Studies that represent results that are reproducible in many other study settings are thought to be _________
externally valid or generalizable
refers to studies that compare two or more treatments that are generally accepted to be effective
Comparative effectiveness
often defined based on disease status or having a risk factor of interest
cohort
subjects receive an active intervention (ie, drug or other treatment)
Experimental studies
first studies performed in humans and are often designed with the notion that they are human pharmacology studies
Phase I studies
goal is to evaluate a drug’s dose range, safety, tolerability, pharmacokinetics, and pharmacodynamics
Phase I studies
also called initial efficacy studies
Phase II studies
conducted to initially determine the effect of an intervention on patients with the disease of interest
Phase II studies
also called comparative efficacy studies,
Phase III studies
designed to assess the efficacy of an intervention compared with that of a “control” treatment (either active treatment or placebo)
Phase III studies
postmarketing studies
Phase IV studies
usually conducted after a treatment obtains FDA approval for marketing
Phase IV studies
They may also be called effectiveness studies because of their focus on how well the approved drug works in the general population and how safe the drug is in a larger population and over a longer period of time
Phase IV studies
also known as large simple studies or Peto studies, are effectiveness studies that focus on understanding how an intervention works in the routine clinical setting
pragmatic trials
are those in which subjects are observed and exposures and outcomes are measured in routine care without any effort to intervene or otherwise influence any measured factors
Observational studies
sometimes called a prospective study,
cohort study
follows a group of patients over time and monitors the effect of a risk factor or exposure on the development of an outcome
cohort study
sometimes also called a retrospective study
case-control study
quantitative study of studies
meta-analysis
It is a systematic review that attempts to combine the results of multiple studies in order to create a pooled effect estimate of an outcome of interest
meta-analysis
frequency of a disease or other outcome of interest over a given period of time
Prevalence
It is measured as the number of individuals with a disease divided by the number of individuals sampled over a specified time period
Prevalence
frequency of new cases of a disease or other outcome among those who are at risk of the disease or outcome of interest within a specified period of time
Incidence
refers to those who have the potential to develop the disease or other outcome of interest
“at-risk population”
typical effect estimate is the
risk ratio or relative risk, also called a hazard ratio
the ratio of the odds that a case is exposed compared with the odds that a control is exposed
odds ratio
proportion of truly diseased individuals (ie, true positives and false negatives) who are defined as having the disease by a test (ie, true positives).
sensitivity
It is also called the true positive rate
the proportion of individuals who truly do not have the disease (ie, false positives and true negatives) who are defined by the test as not having the disease (ie, true negatives).
specificity
It is also called the true negative rate
proportion of individuals who have a positive test that truly have the disease
positive predictive value
proportion of individuals who have a negative test who truly do not have the disease
negative predictive value
What bias is present in this scenario?
In a cohort study evaluating whether a topical therapy used to treat psoriasis is more effective than a systemic therapy, this bias would occur if those selected for treatment with a topical steroid had less severe disease than those selected for the systemic therapy
Selection bias
In a case-control study, this bias can occur if the source population from which the cases are drawn is different from the control source population.
Selection bias
What bias is present in this scenario?
In a hypothetical case-control study evaluating the association between nonsteroidal antiinflammatory drug (NSAID) use and colon cancer, comparing cases of colon cancer drawn from patients admitted to the hospital with control participants drawn from patients with arthritis admitted to the hospital may result in a falsely low effect estimate because the control participants likely have had a high exposure to NSAIDs
Selection bias
What bias is present in this scenario?
In a case-control study evaluating the association between cigarettes and lung cancer, because of previous reports and package warnings about cigarettes, it is likely that those with cancer are more likely to recall and report a history of cigarette use than those without lung cancer.
Information bias
In a cohort study evaluating the risk of cancer among patients with psoriasis, this bias could be introduced if the method of information gathering (ie, psoriasis subjects answer survey questions while waiting patiently for phototherapy) elicits more detailed responses about cancer risk factors, such as cigarette use, in the psoriasis patient cohort than in the cohort of patients without psoriasis (ie, subjects without psoriasis answer survey questions while completing an office visit after a wart treatment).
Information bias
Sometimes called pivotal studies
Phase III studies
Identify the type of RCT
Dutch study of home versus outpatient ultraviolet B phototherapy for psoriasis (PLUTO) 3 and a UK study of prophylactic antibiotics for prevention of cellulitis (PATCH II)
Pragmatic RCT
Identify the study design
in an effort to answer the question of whether or not treatment of acne with isotretinoin increases the risk of developing inflammatory bowel disease (IBD), this study design could be employed.
Cohort study
Identify the study design appropiriate with the scenario:
Individuals with acne and no prior history of IBD who are treated with isotretinoin (the exposed group) could be followed and compared with individuals who have not been treated with isotretinoin (the unexposed group) to determine if there is a difference between the two groups in risk of developing IBD
Cohort study
These studies sample a group with a disease of interest and another that does not have the disease.
Case-control study
The study subjects are then interrogated or preceding data are examined to determine the prevalence of a risk factor
Case-control study
Palmer and coworkers used this study design to identify loss-of-function variants of filaggrin that are associated with atopic dermatitis.
Case-control study
calculated based on the prevalence of exposure in the two groups
effect estimate, typically an odds ratio
particularly useful for studying rare outcomes, take much less time (subjects are not followed for the outcome to occur), and are particularly subject to selection and recall biases
Case-control studies
What is the study design in this scenario:
measuring the prevalence of a particular disease or other outcome in a population
Cross-sectional studies
Quality reporting tools and checklists for systematic reviews or meta-analyses.
- AMSTAR (A Measurement Tool to Assess Systematic Reviews)
- PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses)
- QUOROM (Quality of Reporting of Meta-Analyses)
Quality reporting tool and checklist for clinical trials
CONSORT (Consolidated Standards of Reporting Trials)
Quality reporting tool and checklist for observational studies
STROBE (Strengthening the Reporting of Observational Studies in Epidemiology)
the Cochrane group’s recommended scale for grading quality of evidence and strength of recommendations
GRADE scale
This scale allows for grading of evidence for diagnostic tests, prognostic markers, and harm that many other scales do not
Oxford Centre for Evidence-Based Medicine (OCEBM) scale
how is incidence measured
In a given time frame, incidence is measured by dividing the number of individuals who developed a disease by the number of individuals in the at-risk population
It is the absolute risk in the exposed persons minus the absolute risk in the nonexposed persons.
Attributable risk or risk difference
