Understanding medical diagnosis: why it’s all ‘best guesses’

I thought it might be helpful to take a few steps back and dig into how doctors are trained to think about and look at patients, and how they are trained to make diagnoses.

This is really important because it helps us understand where missteps and mistakes are more likely to happen and to have a deeper understanding of how to ensure that we get properly diagnosed and treated.

The sheer amount of guesswork in medical care can feel deeply disturbing, but it is reality. Misdiagnoses are extremely common(about 1 in 4 diagnoses are wrong), and while some may be a necessary part of the diagnosis process, many are unnecessary and just extend the suffering of patients.

Two paths to diagnosis

There are two different methods that physicians use to diagnose a patient: pattern recognition and differential diagnosis.

Pattern recognition is usually the more reliable method, but for it to work, the doctor needs to have seen and understood the symptoms before – direct experience generally, rather than reading about it in a textbook.

Pattern recognition, for example, is why many older doctors can diagnose pertusis(whooping cough) based on just hearing the patient cough. They know that sound and can instantly place it due to its uniqueness.

The other path is referred to as the differential diagnosis process. It’s a series of educated guesses which the doctor checks through testing.

As a simple example, if a person’s arm is painful after a fall and is being held at an odd angle, the doctor might hypothesize that there’s a break(tentative diagnosis). By x-raying the arm, that guess is either confirmed or proven false.

If the tentative diagnosis is correct, then the patient sees an orthopedist to get the bone reset and likely put in a cast for healing.

If the arm proves not to be broken(tentative diagnosis disproved), the doctor needs to come up with another hypothesis(such as damage to joints or other soft tissue) which will either be tested or accepted as the diagnosis.

If contradictory information occurs later, then the differential diagnosis process starts again until or unless a doctor who recognizes the pattern can make a firm diagnosis – or the problem is resolved.

The dangers and challenges to pattern recognition

When a doctor correctly recognizes a pattern, that’s often when you can feel most at ease about your diagnosis.

My FND diagnosis was that way. The neurologist who diagnosed me was a movement disorder specialist and my main symptoms were strange movements.

He observed how my symptoms worked and when they stopped or increased, and told me how the movements very firmly did not match with the typical patterns for other movement disorders. He had been taught about conversion disorder and seen it in other patients and felt secure in the diagnosis.

Conversion disorder/FND resembles other neurological disorders without having the same cause and the symptoms change or decrease with distraction – all of which he saw in my case.

He recognized the pattern of conversion disorder/FND in my symptoms(and how my symptoms did not match the other movement disorders he was familiar with) and so was able to make a firm diagnosis.

There are two major challenges to pattern recognition: not having experience of the pattern and being prone to see patterns that aren’t there.

The first problem is why the differential diagnosis process exists.

For doctors who haven’t seen patients with specific problems or the many conditions that don’t have easily identifiable indicators(or ones that need to be tested for), the differential diagnosis process is the only option.

The second problem is more chilling. It occurs when the doctor either has what I refer to as a ‘pet’ diagnosis or when the doctor won’t open their mind to diagnoses they are unfamiliar with.

The pet diagnosis problem, I have personal experience with – it was how I was misdiagnosed as having interstitial cystitis(IC). That doctor had IC herself and while it is sometimes challenging to diagnose, this doctor went too far in the other direction and gave tests of dubious value that pushed patients towards being misdiagnosed as having IC.

While she might be a good doctor for people who actually have the condition, she kept seeing the pattern of IC even when it wasn’t there, which led to me being treated for a condition I didn’t have.

There are also doctors who like to believe that they know or understand everything there is to know in terms of medicine. They make their diagnoses and refuse to consider the possibility that they missed something or that there are rare conditions out there that they haven’t heard of.

Those doctors reach points of uncertainty and then refuse to accept them. They insist that they recognize the pattern, even if it’s incorrect – or they insist that the patient must have ‘always been that way’ because they can’t consider the possibility of their patient having a condition they haven’t considered.

In some cases these are sexist or otherwise biased doctors who discount symptoms or whose personality prevents the patient from fully explaining the situation – but always these doctors will refuse to consider additional possibilities, and the only available option is to get another opinion.

The value and challenge of differential diagnosis

Differential diagnosis can also lead to a firm diagnosis. It’s essential for any diagnosis that requires testing or information that isn’t available based solely on direct observation.

Differential diagnosis is the process of weeding out possibilities until there is only one option left to explain the symptoms.

Sometimes, that single option becomes obvious quickly after testing, while other times it’s reached by removing the other possibilities(a diagnosis of exclusion).

Diagnoses of exclusion leaves a bit more uncertainty than ideal, but sometimes they still are the correct answer.

In the broken bone example, if an x-ray shows that the bone is broken, then that first theory was correct, proven by the X-ray.

When my FND first started, I had multiple doctors use the differential diagnosis process to try to figure out what I had, but none of them considered conversion disorder/FND, so they couldn’t do the appropriate comparisons.

The neurologist who did diagnose me was familiar with the condition, which is why he could fit the pieces together and come up with my diagnosis.

For differential diagnosis to lead to recognizing your condition, the doctor needs to be aware of the condition and have the theory that you may have it.

They usually start by testing for common or easily recognized conditions that match your symptoms, but if you don’t match those expectations, that’s when your doctor is really being put through their paces.

The more aware a doctor is of their own limitations, the more likely they are to refer you to a useful specialist or other experts if they can’t find an explanation for your symptoms.

Some doctors run out of ideas and don’t want to admit to their confusion, while others can and will.

Each doctor has their own mental list of possible conditions and their own slightly different interpretation of ‘normal’ results.

Getting diagnosed correctly isn’t always easy, and often requires seeing multiple doctors, potentially with multiple specialties, until you find a doctor who will keep digging until you can find the underlying cause of your condition – which then can be treated.

Diagnosis is often an iterative process, not a singular event

People who aren’t used to chronic conditions often assume that getting a diagnosis is a straightforward process – you go to the doctor, they examine you, and maybe they run a few tests, and then voila, you have a diagnosis and know what’s wrong.

I wish it worked that way, but it really doesn’t.

More often, when you have a problem, you mention it to your doctor, and they examine the issue more closely and come up with a hypothesis, their educated best guess about what’s wrong.

Sometimes they’ll also give you some form of testing to help confirm or deny their theory. It often takes hours to weeks for those test results to come back.

In the meantime, they either provide treatment for their best guess, or they wait for those results. Most people who go into the doctor’s office(pre-COVID19) because of something in the cold/flu family will either be told to rest and drink fluids, or be given an antibiotic if the doctor thinks the infection might be bacterial rather than viral(such as strep throat).

If the condition doesn’t seem to require immediate treatment, the doctor often waits for results to make a decision.

In many cases, the first round of tests may not confirm anything, so the doctor needs to guess again – and check again.

For relatively simple things, it may only be one or two doctors visits to find the source of the problem, but for many with multiple, chronic, or challenging conditions, getting diagnosed can literally take years.

If your primary care physician can’t make a solid diagnosis, they should then refer you to an appropriate specialist in order to have them look over your symptoms and come up with a diagnosis that explains your condition.

Sometimes it takes multiple specialists, and sometimes there are multiple diagnoses. Each doctor you see will often refer to the test results and notes that other doctors provide to help solve the mystery of your condition.

There are some doctors who are recognized as being especially skilled diagnosticians – ones who deeply understand the differential diagnosis process and love to solve the mystery around what you have.

If your regular doctor and/or specialists throw up their hands, you likely need to get a good diagnostician on your team to help you dig out the truth.

Often these are specialists and they focus on their particular type of medicine, but they can do amazing things and push on the edges of their expertise.

Getting Al diagnosed with pernicious anemia required a skilled diagnostician because his body had been ravaged by a silent disease and his symptoms were less common ones.

It did take a lot of testing and a lot of “normal” results to find a problem that would explain his osteoporosis. He only had one odd blood test result: low B12 levels.

He also had to see two different specialists to be able to get the appropriate testing to confirm his eventual diagnosis.

Treating medical conditions

While sometimes doctors quickly reach a useful diagnosis and are quickly able to treat it, more often the diagnosis process is an extensive one lasting for weeks to years. In those longer cases, doctors often prescribe treatments that manage their best guess as to what the condition is.

The treatment itself becomes part of the differential diagnosis process. If the treatment helps, the doctor’s diagnosis was correct, and if it doesn’t, then it’s time to try again with a bit more knowledge.

Doctors are trained to focus on the typical treatments for the average person with any particular condition, so that’s generally what a doctor does – suggest that typical treatment.

At this point, many conditions have a list of medications that may help, and each one will interact slightly differently with the patient’s system.

In most cases, there isn’t a way to know in advance what side effects an individual person may experience, or how effective one medication is likely to be as opposed to another.

Selecting the right medication is a series of best guesses made by the doctor to help their patient.

It’s very important, therefore, to think about the impacts the medication has on you- both the positive and the negative.

In an ideal world, you and your doctor should be a team, working together to determine the best treatment for you, what’s most likely to be helpful, and what side effects may come with your treatment – with thoughts on alternatives if the side effects are too unpleasant.

Protecting yourself with this understanding

Knowing how the process works and how long it can take, I hope that this empowers you to step up and ensure that you are correctly diagnosed by a doctor who is willing to work with you as a team.

You should have a primary care physician who is your teammate in this process- one who respects you listens to you and is always willing to help you find an appropriate specialist if you need one.

If your current primary care physician isn’t fitting the bill, it’s time to go doctor shopping and find one who does. You deserve a doctor who respects you. And yes, it is possible to find one.

Your primary care physician should either recognize the pattern of your symptoms, or use the differential diagnosis process to at least categorize your condition as something a particular sort of specialist should know about.

If your primary care physician doesn’t have the appropriate experience or knowledge base to diagnose or treat your condition, then it’s time to see a specialist.

Just like your PCP, you can usually choose among different specialists based on your insurance plan, so shop around a bit if you need to.

Your specialist should be able to recognize your condition and then suggest an appropriate treatment to help you manage the condition and/or your symptoms.

Once you have a firm diagnosis, you can work with your doctors to form a treatment plan, which includes medication, exercise, appointments/testing, self-care, and often dietary adjustments.

You and your doctor can find the right medication(s) to help you without too many negative side effects, and sometimes if you make the right lifestyle adjustments or develop the right habits, you may eventually not need any medications at all.

The important thing in all of this is to listen to yourself and be willing to have the hard conversations with your doctor if you need to. You also need to remember that you have every right to fire a doctor who isn’t helping you enough.

You deserve a firm diagnosis, and you can get it, as long as you find and work with doctors who will work with you, and who are willing and able to do additional research if needed.