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Epidemiology and biostatistics > Diagnostic tests > Flashcards

Flashcards in Diagnostic tests Deck (11)
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1

Which clinical areas are diagnostic tests applied to

radiological, laboratory, physiological

2

What is sensitivity and specificity

Sensitivity=true positive rate (number of diseased individuals positive to test/total number of diseased individuals)
Specificity=false negative rate (number of disease-free patients negative to test/total number of disease free individuals)

3

Positive predictive value and negative predictive value how to calculate

PPV==number of diseased individuals positive to test/total nummber of individuals positive to test
NPV=number of disease free individuals negative to test/total number of individuals negative to test

4

Draw out a table of the relationships between the terms: sensitivity, specificity, PPV,NPV, accuracy

ref. notes

5

How to calculate positive and negative liklihood ratios

PLR=sensitivity/1-specificity
NLR=1-sensitivity/specificity
If P is the prevalence of diseasePPV/(1-PPV)=P/(1-P)*PLR

6

Equation relating PPV to prevalence of disease and positive likelihood ratio

PPV/(1-PPV)=P/(1-P)*LR+

7

Purpose of predictive value and prevalence of disease

quantify usefulness of test

8

likelihood ratio purpose

combines sensitivity and specificity and is used to compare usefulness of different tests

9

Equation for agreement in qualitative test results

(observed % agreement-expected % agreement)/(100-expected % agreement)

10

Choice of cut off when dichotomising continuous data

choose sensitivity or specificity required. Move cut point to increase sensitivity but decreasse specificity vice versa

11

Bias and precision difference

Bias-mean difference with 95% confidence interval
Precision-standard deviation (or 95% range) of differences