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The Diagnosis of Exclusion

One parenting phrase I sometimes hear is “you’re only as happy as your unhappiest child.”

While I know that the intent of the statement is in regard to emotional/psychological health, I actually think in many ways it applies to physical health as well. When your child isn’t feeling well, neither are you as a parent. Best case scenario is that the problem can be diagnosed and solved quickly and then everyone just moves on. But what if the problem can’t be diagnosed with an xray and a lab test or two? What if the symptoms don’t seem to bundle up into a tidy package that has a straightforward treatment and course? What if, after test after test, things still don’t add up?

Even with all the smart healthcare professionals out there, and all the amazing advances in medicine and technology, this does happen of course, and it is not easy for anyone to manage. It often means multiple trips to different specialists, lots of waiting, and typically an uncomfortable test …or several. When results all end up normal or negative and the symptoms persist things can get frustrating in a hurry, although it’s important to point out that knowing what it ISN’T is just as important as knowing what it is. Coming to a final diagnosis can be a windy road full of detours and dead ends, and sometimes when that happens we arrive at what we call a DIAGNOSIS OF EXCLUSION.

What is this?

It’s a diagnosis that is typically only made by the process of elimination, once all other options are exhausted, so only after tests come back that would point to other medical problems end up being negative. Then and only then do we make this diagnosis. Usually medical conditions that are classified as diagnoses of exclusion are ones where there is no definitive test. What typically happens is that after an extensive medical workup with no concluding results, clinicians start to think about other, more unusual causes. Then, mostly based on the history and physical exam, the diagnosis of exclusion is made.

Chronic Fatigue Syndrome

How about an example-? A common one that many are familiar with is chronic fatigue syndrome (CFS). First of all, some people question whether or not this syndrome is really a legitimate medical “thing’ at all. This is often the case with diagnoses of exclusion, because as I said earlier, there’s no test to prove its existence. So the way that chronic fatigue syndrome gets diagnosed is by performing lots of other tests—like thyroid function tests, other general blood tests, and even perhaps a head CT scan—to make sure there’s no other attributable source for the symptoms—and if those all come up normal then CFS may end up as the diagnosis. At that point, symptom-targeted treatment may be initiated as an empiric trial to measure improvement (if any). This can help confirm the diagnosis.


Let’s look at another example, this time in children. There’s an unusual food allergy in children called “FPIES” which stands for Food Protein Induced Enterocolitis Syndrome that on the outside looks like a child is sick with a stomach virus: lots of vomiting and diarrhea several hours after eating. There’s no magic test to diagnose this disorder and if you think about it, when a child has these symptoms several HOURS after eating, an allergic reaction (usually occurs right away after exposure) isn’t the first thing you think of.

The way the diagnosis is arrived at isn’t necessarily by any specific testing but more by detective work in the child’s history and the determination that symptoms occur every time a child ingests a certain food, and there are common culprits (soy, grains). Once that symptom pattern occurs repeatedly it typically takes an astute clinician to suggest the possibility. Then the symptom pattern is compared to diagnostic criteria (these exist for some unusual disorders) and the final diagnosis is either confirmed or rejected.

While most of the time children outgrow FPIES, they often must avoid the exacerbating food so as not to incur symptoms. Strange though, right—here’s an allergy diagnosis that doesn’t cause typical allergic symptoms and you don’t get any positive results from allergy testing. It’s a diagnosis of exclusion, made only after the determination that the symptoms aren’t being caused by an actual stomach virus, other metabolic disorder, or something else altogether.

To Conclude…

It’s important to know about the concept of “diagnosis of exclusion” because it’s a reminder that medicine isn’t perfect and that answers can indeed sometimes be found in circumstances where it may seem like the events in the evaluation were just a wild goose chase of negative lengthy testing. Stay committed to and patient with the process, and in the majority of cases the answer is ultimately figured out, one way or another.

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About the Expert

headshot of Dr. Christina Johns

Dr. Christina Johns is a nationally recognized pediatric emergency physician and Senior Medical Advisor at PM Pediatric Care. An official spokesperson for the American Academy of Pediatrics, she is board certified in both pediatrics and pediatric emergency medicine. With extensive media experience, the proud mom of two teenagers shares over 20 years of pediatric expertise with patients and families everywhere. Follow Dr. Johns for more insights on children’s health!