Evaluating Tests & Measures Flashcards
Why is there no tertiary prevention screening programs?
Bc it would be too late by then and it wouldn’t really make a difference
What is the ultimate goal for epidemiology?
Description
Causation
Prevention
What is the purpose of screening?
To halt or slow down the disease process through detection of disease
What is the assumption of screening?
That it won’t be affective or it would be false as well wouldn’t make a difference
Give two examples of successful screening programs
Mammogram - breast cancer
Pap smear - cervical cancer
PSA - prostate cancer
What are two measures of validity?
Sensitivity
Specificity
What is the difference between screening and diagnostic testing?
Screening is not definitive - would state if you may get the disease etc
Diagnostic is definitive - would state if you do have the disease etc
Sensitivity formula
Ppl with the disease
Specificity formula
Total population w/o disease
A screening test has 90% sensitivity and 75% specificity, interpret this values.
Sensitivity - 90% correctly identified positive cases with disease
Specificity - 75% correctly identify those without the disease
What are true positives?
You for sure have the disease
What are true negatives?
You for sure don’t have the disease
What are false positives?
It says you have the disease but you don’t
What are false negatives?
It says you don’t have the disease but you do
How do we determine the best cutoff point to decide positive or negative screening results?
Compromise btwn specificity and sensitivity
Choose of the cut off usually results in misclassification of cases or bias
Positive predictive value formula
True positive + true negative
Negative predictive value formula
False positive + false negative
How do you interpret PPV and NPV?
PPV - % of ppl truly have disease
NPV - % of ppl who truly do NOT have the disease
How does the prevalence affect the predictive value?
Higher the prevalence the more precision, sensitivity & specificity
What does sequential testing accomplish?
Screening test are not definitive so people who do test positive they get more testing done in order to confirm and it reduces # of false positives and the second test is usually more expensive bc it’s also more accurate and invasive
To hit group(s) of people do we apply the second test in sequential testing?
Those who testing positive
What are the criteria for successful screening program?
Disease is an important health prob Accept treatment for patient w/disease Available facilities for diagnoses & treatment Effective interventions High sensitivity & specificity Acceptable screening tests to the pop Understanding natural history of disease
