What is a cross sectional study? What can it be used to measure?
Assesses frequence of disease (or other factors) in a group of people at a particular point in time - What is happening?
Measures disease prevalence - shows risk factor association with disease NOTE correlation =/= causation
What is a case control study? What does it measure?
Compares group with disease to control - Looks for risk factor
Measures Odds ratio
What is a cohort study? What does it measure?
Compares group with risk factor to group without risk factor. Looks to see if exposure increases likelihood of disease. Can be retrospective or prospective.
Measure relative risk - e.g. smokers had higher risk of developing COPD than non smokers.
What is a twin concordance study? What does it measure?
Compares the frequency with which both monozygotic twins or both dizyogtic twins develop the same disease;
Measures nature vs nurture
What is an adoption study? What does it measure?
Compares siblings raised by biological vs adoptive parents
Measures nature vs nurture
What does a triple blinded clinical trial entail?
Blinding of patients, doctors and researchers analyzing the data
What is the purpose of a phase I clinical trial?
Assesses safety, toxicity, pharmacokinetics and pharmacodynamics
What is the purpose of the phase 2 clinical trial?
Assesses treatment efficacy, optimal dosing and adverse effects
What is the purpose of phase 3 clinical trials?
Compares new treatment to current treatment or placebo
What is the purpose of phase 4 clinical trials? what does it involve?
Postmarketing surveillance of patients after treatment is approved.
Detects rare or long term adverse efects
Define the sensitivity of a test.
Probability that a test detets a disease when disease is present.
SN-N-OUT = a highly SeNsitive test, when Negative, rules OUT disease
Define the specificity of a test
Probability that the test detects no disease when disease is absent.
SP-P-IN = a highly SPecific test, when Positive, rules IN disease
Define positive predictive value
Probability that a person actually has the disease when given a positive test result
Define negative predictive value
Probability that person actually is disease free when given a negative test result
Define incidence and prevalence
Incidence - no of new cases / no of people
Pevalnce = no of existing cases / no of people at risk
Define odds ratio
Odds tht the group with the disease was exposed to a risk factor divided by odds that the group without the disease was exposed
Define the relative risk
Risk of developing disease in exposed group divided by risk in unexposed group
Define the attributable risk
difference in risk between exposed and unexposed groups
Define relative risk reduction
Proportion of risk reduction attributable to the intervention as compared to a control
RRR = 1 - Relative Risk
Define absolute risk reduction
Difference in risk attributable to the intervention as compared to a control
ARR = (c/c+d) - (a/a+b)
Define the number needed to treat
Number of patients who need to be treated for 1 patient to benefit
Define the number needed to harm
number of patients who need to be exposed to a risk factor for 1 patient to be harmed
Define precision of a test
absence of random variation in test
Define the accuracy of a test
Trueness of test measurements
What is the berkson bias?
Study population selected from hospital is less healthy than general population
What is the healthy worker effect?
Study population is more healthy than general population
What is the non response bias?
participating subjects differ from nonrespondents in meaningful ways
How would you reduce selection bias?
Ensure the choice of the right comparison group
How would you reduce recall bias?
Decrease time from exposure to follow up
What is measurement bias and how would you reduce it?
Info is gathered in a way that distorts it
Reduced using a standardised method of data collection