Module 11 - Medical Decision Making Flashcards
(23 cards)
What is a screening test?
Used to detect disease at earliest stages among asymptomatic persons in general population
What is a diagnostic test?
Used to confirm a diagnosis among persons with existing signs or symptoms of illness
What is a synonym for validity?
Accuracy
What is a synonym for reliability?
Precision
What is test validity (aka accuracy)?
How well a test or instrument or procedure measures what it says it is measuring
What is internal validity?
The extent to which you are able to say that no other variables except the one you’re studying caused the result.
What is external validity?
The extent to which the results of a study are valid for the population from which the sample was drawn (i.e. how generalizable are the results)
What are common threats to external validity?
Examples of how you might be wrong in making generalizations. Threats include people, places, times
What is reliability?
The degree to which a measurement is immune from random variation
What is a false positive and how does it relate to type 1 error?
A person who tests positive but does not have the disease, is equal to type 1 error and also equal to the alpha level set for the test
What is a false negative and how does it relate to type 2 error?
A person tests negative but they really do have the disease. This is equal to the type 2 error and is also equal to 1-alpha level. This parameter is known as Beta.
Sensitivity
Proportion of individuals with disease who test positive, measure of true positive rate
Specificity
Proportion of those without disease who test negative, measure of true negative rate
How does false negative rate relate to sensitivity?
False negative rate = 1 - sensitivity
How does false positive rate relate to specificity?
False positive rate = 1 - specificity
Which type of test is used for screening?
A very sensitive test is used to screen for disease or to rule out the disease
SNNOUT: if a person tests negative using a highly sensitive test, you can rule out that disease for that person
Which type of test is used for diagnostic purposes?
A very specific test shoul dbe used to confirm or rule in a disease.
SPPIN: a person who tests positive using a highly specific test should be considered as having that disease
What tool would you use to determine the cutoff point for sensitivity and specificity?
A ROC curve - each point on curve corresponds to pair of sensitivity and specificity at that cutoff. The pair should be chosen based on whether you are screening or diagnosing.
What is PPV?
The probability that a person actually has the disease given a positive test result
What is NPV?
The probability that a person does not have the disease given a negative test result
What is the prevalence?
The proportion of individuals with disease to the total population
If the prevalence of a disease is high, what effect will this have on the PPV and NPV?
PPV will be high, NPV will be low
If the prevalence of a disease is low, what effect will this have on the PPV and NPV?
PPV will be small
NPV will be large
