Sensitivity and Specificity

This is a topic that I think doctors- both of the human and animal professions do not explain very well.  Another thing we don't explain very well is about testing, and the consequences of testing.

A highly sensitive test means it will "catch" all of the positives for a disease and a few (or even quite a few) false positives.  A highly specific test means if it says it's positive, it's positive, but it might come out as negative when it's really positive (or a false negative, if that's not confusing).

If you come up positive on a sensitive test, you might find yourself quite scared for a bit and then find out your diagnosis was incorrect.  You might even get put on medication that isn't necessary or even worse, could hurt you.  That's why most of the time if we perform a sensitive test, we try to follow it up with a specific test for confirmation.

There has been talk about breast cancer screening, prostate screening and colonoscopy screening and that some organizations are actually advocating reducing screening and increasing the time between screenings.  While it's easy to think this is due to a embattled health care system and cost issues, there are actually some legitimate reasons to think that maybe we screen too much.

First of all, is the issue is that not all screening tests are without risk.  I actually knew someone who went in for a colonoscopy screening, and due to a medical error walked out with a colostomy bag for the rest of their life.  That's obviously a extreme circumstance, and I still plan to get colonoscopies as I get older, especially if I ever develop clinical symptoms.  I don't mean to talk anyone out of screenings.  They can save people.  I'm just trying to discuss that everything should have a cost-risk analysis that should be discussed with your doctor.

Breast cancer screenings have radiation.  They are highly recommended for people with a family history of breast cancer.  They also can expose people to extra radiation, which can cause cancer. It seems kind of like a catch-22.  In looking for cancer, you can increase your risk of cancer.  Again, this is an individual's responsibility to talk with their doctor.  In my case, I had a aunt who died of breast cancer.  I spoke with my doctor about mammograms and she went over the thinking that yes, we still do them, but not as early on in a woman's life and not as frequently unless there is a clearer genetic risk.

Sometimes the treatment for things is worse than the disease. I sometimes find myself looking at blood work on a pet and feeling stuck between a rock and a hard spot.  I'm a doctor.  I'm supposed to treat disease, but in a pet that is feeling great and the only problem is their lab work isn't normal, I have to have a careful conversation with the owner.  A disease, such as Cushing's Disease, or hyperadrenocorticism can cause problems like increased thirst and urination, obesity and higher risk of infection.  It can be worthwhile to treat if the pet is experiencing medical problems from it.  However, if the pet is just a little overweight and otherwise happy, I'm less inclined to put them on medication that is actually meant to kill their adrenal glands and may send them into a life-threatening crisis.

There are many diseases where the treatment and side-effects can be worse than the disease.

I recently had personal experience with a doctor wanting to do numerous tests on me.  I went in for one concern and the doctor wanted to test over $5,000 in testing that with my medical knowledge was not related to my concern.  I tried to ask for the reason for some of the testing.  I don't have a problem paying for something that is beneficial, but from personal experience, I do have a problem with unnecessary testing.  If you are on a fishing expedition, you are bound to catch something.  It could also be completely unrelated to whatever you were looking into.  It could (and it has) in my case sent me down rabbit holes of unnecessary diagnosis, treatment and consequences.  As I say often to my patients, "There is some truth in- if it aint broke, don't fix it."

Astonishingly, when I asked the reasoning for the tests, the answer I got was, "Because the doctor said so."  I guarantee you if I ever used that as a reason for doing anything to my patients, that would not go over well.  After 2 weeks and about 5 phone calls,
I was able to get in contact with someone who had a little bit more knowledge.  We discussed that my medical issue they wanted to investigate was well managed and of little concern to me at this time.  Furthermore, I informed them that my husband and I were trying to get pregnant and I knew that the medical treatment they were interested in putting me on would be contraindicated.  It was a nice, civil conversation in which I basically said, "Please investigate the issue I came in for and maybe I will look into those other things later, but not at this time."

I share this information not because I enjoy putting my personal experience out there, but I realize that I'm blessed to have the medical knowledge and experience to understand these situations and articulate them with the medical profession.  I share this information to empower others.  I'm not discouraging people from doing diagnostic testing and I recommend tests far more often than I discourage them in my profession.  I do believe though, that one of the keys to improving our healthcare situation- the cost of healthcare, the care that we get; is to empower people to have conversations with their doctors.  It is your right to understand what is being done, what the consequences are and if the treatment is worse than the disease.  Empowerment to understand and own your healthcare is a key to better healthcare.


This post is NOT designed to give medical advice.  I am not a licensed human medical professional and am not qualified to give people medical advice.  Every reader should consult with their doctor regarding the best decision for them.  This post is just advocating that you HAVE a conversation with your doctor regarding the best decision for you, as an individual.