Please enter data into the 2 by 2 table
to determine the likelihood ratio

		Disease
		Present	Absent
Test	given
	not given

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Positive Likelihood Ratio:
Negative Likelihood Ratio:

Likelihood Ratios
The likelihood ratio for a test result compares the likelihood of that result in patients with disease to the likelihood of that result in patients without disease.

So how much do LRs change disease likelihood?

High LRs	Low LRs	Impact on Likelihood
>10	<0.1	Large
5-10	0.1-0.2	Moderate
2-5	0.2-0.5	Small
<2	>0.5	Tiny
1	1	No Change

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Formulas
Positive Likelihood Ratio= (a/(a+c)) / (b/(b+d))
Negative Likelihood Ratio= (c/(a+c)) / (d/(b+d))
- or -
Positive Likelihood Ratio= (sensitivity)/(1-specificity) = TP/FP
Negative Likelihood Ratio= (1-sensitivity)/(specificity) = FN/TN

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