# ruling in vs ruling out

#### johndoe3344

##### Full Member
10+ Year Member
Can someone explain the terms 'ruling in' and 'ruling out' to me?

I don't mean the mathematics or what the formula is, or any of the 2x2 tables for sensitivity and specificity. I memorized all of that and I can apply it perfectly fine, I just don't intuitively understand the meaning of the words to 'rule in' and to 'rule out'

For example, for all the kids that come to my office with sore throat and fever, I do a strep test. What's the purpose of the test -- am I 'ruling in' or 'ruling out' strep?

#### projectlogic

##### Full Member
Can someone explain the terms 'ruling in' and 'ruling out' to me?

I don't mean the mathematics or what the formula is, or any of the 2x2 tables for sensitivity and specificity. I memorized all of that and I can apply it perfectly fine, I just don't intuitively understand the meaning of the words to 'rule in' and to 'rule out'

For example, for all the kids that come to my office with sore throat and fever, I do a strep test. What's the purpose of the test -- am I 'ruling in' or 'ruling out' strep?

If a test has HIGH SENSITIVITY and the result comes back negative, then you can be fairly certain that the patient does not have the particular disease that you are testing for. In other words, you RULE OUT the disease in your list of differentials (it's unlikely that the patient has that disease).

On the other hand, if a test has HIGH SPECIFICITY and the result comes back positive, then you can be fairly certain that the patient most likely has that particular disease that you are testing for. So you RULE IN or keep it on your list of differentials.

#### shan564

##### Full Member
10+ Year Member
If a test has HIGH SENSITIVITY and the result comes back negative, then you can be fairly certain that the patient does not have the particular disease that you are testing for. In other words, you RULE OUT the disease in your list of differentials (it's unlikely that the patient has that disease).

On the other hand, if a test has HIGH SPECIFICITY and the result comes back positive, then you can be fairly certain that the patient most likely has that particular disease that you are testing for. So you RULE IN or keep it on your list of differentials.

Good explanation.

#### msIngrid800

##### New Member
I learn (then forget) the concept, but I find this keyword association gets the right answer 99% of the time:

SPin - SNout

If the question says "blah blah blah, rule in a diagnosis" the answer is good SPecificity.
If the question says "blah blah blah you want to rule this out" the answer is good SeNsitivity.

It makes my brain hurt to figure out the math, so I just use this shortcut and cross my fingers...not that I'd recommend you do the same

#### bettertomorrow86

##### New Member
sorry this is a very old thread but i have one additional question to it.

is it important that the test is JUST HIGH in specificity (rule in)/ sensitivity (rule out).. without any other requirements?

f.e. can you say: HIGH sensitivity and middle specificity -> rule out and HIGH sensitivity and low specificity -> rule out? or is it different then?

This thread is more than 4 years old.

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