Evidence Based Practice Flashcards
What is an incidence rate?
The measure of occurance of a new cases of a disease
We dont count people who already have the disease
Only works when the population is stable
What is incidence density?
Number of new cases of the disease within a specific time period
Used when the population isnt stable!
What is point and period prevelance?
Point –> Proportion of people who have a disease at a specific point in time
Period –> Number of people who have the disease in a time period, divided by by the population at the mid-point
What is the difference between absolute measures and relative measures?
Absolute –> Absolute risk reduction (eg, NNT/NNH)
Relative –> Ratios
What is a confidence interval?
A range of values of which we can be 95% confident that the real value is in-between
What is the point of no difference for absolute and relative measures?
Absolute –> 0
Relative –> 1 (as a ratio)
What is an observational study?
A non-experimental study
Lack of control over the exposures that are assigned
Confounding will occur
What is a cohort study?
An observational study
A population is picked that dont have the outcome (eg, bowel cancer) and then you pick an exposure and see the outcomes of those that were exposed to it and those that weren’t
It must be a certainty that nobody has the end outcome at the start! (can be difficult with things like cancer that could be present….just not diagnosed yet)
What are the strengths and limitations of cohort studies?
Strengths –> Multiple effects can be studied, Incidence rates and relative risks (RR) can be calculated
Limitations –> Difficulties with loss due to follow up (often a very large follow up period), Can have problems with bias, exposures can also happen after diagnosis (eg drinking to cope with a cancer diagnosis)
What are the 9 parts of Hill’s Aspects of Association?
What is a Case-Control Study?
When 2 populations (one with the outcome and the other without) are compared and the exposures looked at over a period of time
An observational study
What are the controls in a Case-Control Study?
Those who do not have the disease, but are otherwise comparable to the cases of those with the disease
Often matched up with gender, age etc
Can bring in bias, as you need to pick the controls (eg, where they are from) appropriately
How is an odds ratio worked out in a Case-Control Study?
What are the advantages and disadvantages of Case-Control Studies?
What is bias?
A systematic error in data
Pulls the risk estimate away from its true value
What is a potential type of selection bias?
Volunteer Bias
Volunteers choose to be in the study…..but is this population different to your everyday person?
What is the effect of differentional and non-differential misclassification?
Differentional (different misclassification for both groups) –> Can cause under or over-estimation
Non-Differentional (missclarification of the same degree for all groups) –> Will cause underestimation
What is a confounder?
A risk factor for the disease and is correlated with the exposure independent of the disease
What does an equal ‘estimated’ OR suggest?
That a confounder is present
When does effect modification occur?
When the effect of the exposure is different in different groups of the population (eg, men and women)
So no average ‘true value’
What are the 2 different categories of consequences when clincal trial outcomes go wrong?
Visible Consequences –> Allowed onto the market, leading to an increase in morbidity/morality
Not Visible Consequences –> Medicine is not marketed, so you have lost a chance to reduce morbidity/morality
What is phase IV of clincal trials?
Looking for ADRs and long term harm after the drug has been marketed to the public
What are the 3 types of Adverse Reaction?
A –> Drug Effect
B –> Patient Reaction
C –> Where the drug increases the frequency of spontaneous disease
What is a Proportional Reporting Ratio (PRR)?
Proportion of reactions of for the drug of interest compared to all drugs in the database
The higher the PRR the greater the strength of the signal
Could we assume that both of these drugs are teratogenic?
No!
As we cannot assume a drug class effect when it comes to birth defects (Glutethide is not teratogenic)
What is a pregnancy exposure register?
Women choose to be put onto a register when they take a specific drug (eg, lamotrigine) in pregnancy, and then they are followed up and seen if there are any birth defects or not
What is Relative Risk (RR)?
The likelyhood of getting in the outcome if you are exposed
