The positive likelihood ratio is the probability of a person who has the disease testing positive divided by the probability of a person who does not have the disease testing positive. (I.e. true positives/false positives).

	Disease Present	Disease Absent
Test result Positive	a	b
Test result Negative	c	d

+LR = [a/(a+c)] / [b/(b+d)]

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The Compendium platform was created by David Kwinter, MD, CCFP(EM).