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Flashcards in Segars: Screenings in Medicine Deck (17)
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What does a patient want to be told when they get screened for a disease?

-The truth!


What 2 questions should patients ask their physician when a medical screening test is recommended?

-how accurate is it?
-When the test results are announced, how confident will you be in your prediction of whether I do or don't have the disease?


What is true positive?

-test is positive and the patient does have the disease
-Box A


What is False positive?

-test is positive but the patient does not have the disease
-Box B


True negative

-negative test
-pt doesn't have the disease
-box D


False negative

-negative test
-but the pt does have the disease
-box C


What will the numerator be?

-either box A or D


What is sensitivity and specificity related to?

-the test itself


What does positive or negative predicitive values do?

-predicts the accuracy of diagnosis (based on known test result)
-remember, boxes A and D are the numerators


What is sensitivity

-how well a test can detect preence of disease when in fact it is truly present
-proportion of time that a test is positive in a pt that is known to have the disease
-TP/(everybody that has disease)*100%


What is specificity?

-how well a test can detect absence of disease when in fact it is truly absent
-proportion of time that a test is negative in pt that is known to not have the disease
-TN/(all non-diseased... like TN and FP)*100%


What is a positive predictive value (PPV)?

-how accurately a positive test predicts the presence of disease in a pt with a positive test result
-proportion of true positives in a pt that tests positive (correct prediction)
-PPV=TP/(all positive tests)


What is negative predictive value (NPV)?

-how accurately a negative test predicts the absence of disease ina pr with a negative test result
-proportion of true negatives in a pt that tests negatvie (correct prediction)
-NPV= (TN/(All negative tests))


What is Diagnositc accuracy/diagnostic precision?

-Proportion of patients that are correctly identified as either having truly having disease (TP) or truly not having disease (TN) out of all pts screened
-(TP+TN)/(all patients)*100%


How do we figure out if it is a column total or row total that we will be dealing with?

-with sensitivity or specificty, there will be something about absolute truth... column totals


What is validity?

-getting it right.... telling the truth
-getting it in boxes A and D


What is reliability

-ability of a test to give the same result on repeated uses
-a valid test is always reliable, yet a reliable test is not always valid