"A positive likelihood ratio (LR+) is the probability that someone with a disease will have a positive test result divided by the probability that someone without a disease will have a positive result."
"A negative likelihood ratio (LR-) is the probability that someone with a disease will have a negative test result divided by the probability that someone without a disease will have a negative result. The formula for a positive likelihood ratio is:"
"The higher the positive likelihood ratio (LR+), the more likely that someone testing positive has the disease in question. The lower the negative likelihood ratio (LR-), the more likely that someone testing negative does not have the disease in question. An LR+ or an LR- of one means that people with and without disease are equally likely to test positive or negative respectively. Likelihood ratios of one mean that a test cannot discriminate between those who do and those who do not have the disease. As a general rule, an LR+ greater than 10 and an LR- less than 0.1 show that a test reliably discriminates between people who do and do not have disease. If we know the pretest probability of disease, we can use LR+ to calculate the post-test probability of disease among those who test positive using the following formula: Post-test odds = pretest odds x LR+."
"The higher the positive likelihood ratio (LR+), the more likely that someone testing positive has the disease in question. The lower the negative likelihood ratio (LR-), the more likely that someone testing negative does not have the disease in question. An LR+ or an LR- of one means that people with and without disease are equally likely to test positive or negative respectively. Likelihood ratios of one mean that a test cannot discriminate between those who do and those who do not have the disease. As a general rule, an LR+ greater than 10 and an LR- less than 0.1 show that a test reliably discriminates between people who do and do not have disease. If we know the pretest probability of disease, we can use LR+ to calculate the post-test probability of disease among those who test positive using the following formula: Post-test odds = pretest odds x LR+."
"The higher the positive likelihood ratio (LR+), the more likely that someone testing positive has the disease in question. The lower the negative likelihood ratio (LR-), the more likely that someone testing negative does not have the disease in question. An LR+ or an LR- of one means that people with and without disease are equally likely to test positive or negative respectively. Likelihood ratios of one mean that a test cannot discriminate between those who do and those who do not have the disease. As a general rule, an LR+ greater than 10 and an LR- less than 0.1 show that a test reliably discriminates between people who do and do not have disease. If we know the pretest probability of disease, we can use LR+ to calculate the post-test probability of disease among those who test positive using the following formula: Post-test odds = pretest odds x LR+."
"The higher the positive likelihood ratio (LR+), the more likely that someone testing positive has the disease in question. The lower the negative likelihood ratio (LR-), the more likely that someone testing negative does not have the disease in question. An LR+ or an LR- of one means that people with and without disease are equally likely to test positive or negative respectively. Likelihood ratios of one mean that a test cannot discriminate between those who do and those who do not have the disease. As a general rule, an LR+ greater than 10 and an LR- less than 0.1 show that a test reliably discriminates between people who do and do not have disease. If we know the pretest probability of disease, we can use LR+ to calculate the post-test probability of disease among those who test positive using the following formula: Post-test odds = pretest odds x LR+."
Expected headings
"Example"
"There are 2 types of likelihood ratios, positive and negative:"
"There are 2 types of likelihood ratios, positive and negative:"
"If a cancer screening test has 90% sensitivity and 80% specificity, then LR+ = sensitivity / (1-specificity) = 0.9 / (1-0.8) = 0.9 / 0.2 = 4.5: this means that someone with the disease is 4.5 times as likely to test positive as someone without the disease. The LR- =( 1-sensitivity) / specificity = (1-0.9) / 0.8 = 0.1 / 0.8 = 1.125: this means that someone with the disease is 0.125 times as likely to test negative as someone without the disease."