rule in, rule out

[surgok]

For some reason, no matter how much I look at it, I don't seem to grasp this concept very well.
I can just memorize SPPIN/SNNOUT, but I'd rather learn the concept if I can.
Someone care to elaborate this in plain simple term? Thanks!

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[dyspareunia]

Sensitivity = rule out = "snout". A highly sensitive test is one that does not miss any true positives, meaning there are no false negatives.

100% sensitivity means everyone with HIV tests positive for HIV. There will be many false positives, but no false negatives. Therefore, a highly sensitive test "rules out" a disease because if the test says you don't have it then you probably don't have it.

Specificity = rule in = "spin". A highly specific test is one that has no false positives.

100% specificity means everyone that's HIV free will test negative for HIV. There will be many false negatives, but no false positives.

 

[Missorleans]

For some reason, no matter how much I look at it, I don't seem to grasp this concept very well.
I can just memorize SPPIN/SNNOUT, but I'd rather learn the concept if I can.
Someone care to elaborate this in plain simple term? Thanks!

If you want to rule out a disease, then you want a test that has a high probability of detecting the disease if it is there. Sensitivity is the number that test positive and have the disease/total that have the disease. So we use tests that have high sensitivity because it is less likely that we will miss any diseased persons.

Might not be the best explanation but that's how I remember it. Since I know sensitivity I just remember that specificity is the opposite: number that test negative and are not diseased/ total without disease.

 

[surgok]

Sensitivity = rule out = "snout". A highly sensitive test is one that does not miss any true positives, meaning there are no false negatives.

100% sensitivity means everyone with HIV tests positive for HIV. There will be many false positives, but no false negatives. Therefore, a highly sensitive test "rules out" a disease because if the test says you don't have it then you probably don't have it.

Specificity = rule in = "spin". A highly specific test is one that has no false positives.

100% specificity means everyone that's HIV free will test negative for HIV. There will be many false negatives, but no false positives.

Makes more sense now. Thanks!