Testing for Diagnosis and Screening Flashcards Preview

Contemporary Practice of Medicine > Testing for Diagnosis and Screening > Flashcards

Flashcards in Testing for Diagnosis and Screening Deck (19):

Sensitivity and specificity

Sens - percentage of people who do have a disease that test positive

Specificity - percentage of people that DO NOT have the disease that test positive


Screening and confirmatory tests

Screen - maximize sensitivity

COngirm - maximize specificity


Advantages of sequential testing

Lowers overall sensitivity and raises specificity


How does prevalence change

Higher prevalence - means great PPV

Lower prevlaence - means lower PPV and higher NPV


Likelihood ratio

Used to asses value of a given diagnostic test


Positive and negativel ikleihood ratio

Sensitivity/1-specifcity for positive

1-sensitivity/specificity for negative likelihood

Can use Fagan nomogram


Strong moderate and weak

Also unhelpful

Strong - 10-infinity or .1 to 0

Mod - 5-10 or .1 to .2

Weak - 2 to 5 or .2 to .5

.5-2 is generally unhelpful


Diseases that can be screened

Important health problems (high incidence or mortalitiy)
Tx more bebenficial in early stages compared to later
Early dx impoves QOL or survival


Appropriate screening tests

Simple, safe, and precise
Can detect the latent or early sx stage
Beneift outweight physical or psych harm


Screening benefits

Disease incidence or mortality
Increase in life expectancy (standard is over 1 month gain)...avoid screening if life expectancy less than 10 years


Screening harms

Adverse effects of screening
Overdx of disease
False positive screening tests


Screening program rationale

Cost is balanced in relation to expenditures
Systematic plan for monitoring program
Participant edu about benefits and disadvantages


Simultaenous testing

Screening test emphasis on sensitivity and sacrifice PPV

Cotesting will raise sensitivity and lower specificty


Overdiagnosis bias

Makes it look like mortality lower because we are including people who were asymptomatic in the orginal group...you find the true positives who are asymptomatic


LEad time bias

Outcome is the same but it looks like the survived with the disease longer because the diagnosis was made earlier in their life

Could artificially inflate the benefit of the results


Length bias

Due to different types of diseases

Will capture more slowly progressive cases than rapidly progresing


All ture positives and negatives

Maximizes sensitivity while minimizing specificty


Clinically meaningful ositives and negatives

Minimizes sensitivity while maximizing specificty


RCTs vs cohorts

Cohorts - healthy used

RCTs - outcome should be cancer mortality in the overall population and NOT survival or cancer case fatality rate