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33 Cards in this Set
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 Back
What would a 100% sensitive test do?

Always detect disease when present


What would a 100% specific test do?

Always exclude disease when absent.


How is diagnostic testing different from screening?

Diagnostic tests symptomatic individuals
Screening tests individuals before symptoms start 

What is the purpose of doing a diagnostic test?

To move the estimated probability of disease toward either end of the probability scale.


When setting up a calculation chart for diagnostic testing:
What goes on the y axis x axis? 
Y = test pos or neg
X = actual disease pos or neg 

Define sensitivity:

The probability that a person with the disease will have a positive test.


Formula for sensitivity:

A/A+C


What is specificity?

The probability that a person without the disease will have a negative test.


Formula for specificity:

TN / TN + FP


What is PPV?

Pos predictive value  the probability of DISEASE given a pos test result


What is NPV?

Probability of NOT having disease given a neg test result


Formula for PPV/NPV

PPV = A/A+B
NPV = D/C+D 

Changing Prevalence of a disease affects what?

NPV and PPV  not sensitivity or specificity


So PPV/NPV depend on:

Sensitivity
Specificity Prevalence 

Prevalence formula:

A + C
 Total 

How do PPV and NPV change when you increase disease prevalence?

PPV goes up as prevalence does
NPV goes down 

Screening tests are for

Asymptomatic individuals


Diagnostic tests are for

Symptomatic individuals


What is Bayes' theorem?

The PPV of a test given a certain prevalence.


If a disease is rare, prevalence is low in a population, what will you see more of?

Falsely positive tests


What is Primary Prevention?
Give an example 
Measures to prevent disease from occurring; an example is vaccination.


What is 2ndary prevention?
Give an example 
Early identification of disease to prevent progression or reduce disability
Mammography 

What is Tertiary prevention?

Treatment or rehab once a disease has occurred, to minimize sequelae or recurrence.


When is primary prevention appropriate?

Before the true onset of disease


When is secondary prevention appropriate?

Between the true onset of disease and clinical onset.


When is tertiary prevention appropriate?

After the clinical onset of disease, but before late stages.


Mammography, clinical breast exams, and self breast exams are:

2ndary prevention techniques to detect developing breast cancer.


What type of prevention is BRCA genetic screening considered?

Primary


What is Tamoxifen?

Tertiary


What are the first 2 criteria for an effective screening test that have to do with the disease itself?

1. Morbidity/Mortality must be of sufficient concern to public health
2. Disease prevalence sufficient 

What 2 criteria for an effective screening test have to do with the test?

1. The test must be sufficiently sensitive and specific
2. The test must be safe and acceptable 

What 2 criteria for an effective screening test concerns the diagnostic workup?

The workup must be acceptable given the number of false positives.


Most important riteria for an effective screening test:

Preclinical intervention must improve outcomes.
