Getting the most from your doctor- How do doctors make a diagnosis

A better understanding of how doctors make diagnoses can help the consumer get the most out of a doctor visit.

A better understanding of how doctors make diagnoses can help the consumer get the most out of a doctor visit.

By no means am I suggesting that patients need to know how to make a diagnosis but rather that a better understanding of the mechanics of the process may help avoid unnecessary waste of time and money in trying to provide care.

Testing has a greater role in preventive care where the goal is to look for problems before symptoms begin.

So what is a diagnosis? A diagnosis is the final conclusion of all the facts in the case. Pneumonia, appendicitis, asthma are all examples of diagnoses. This is the disease process that will be treated.

There are many misconceptions within the general public with regards to how a doctor arrives at a diagnosis. Ask most non medical consumers and they will say that the diagnosis was made by a test like a blood sample or an imaging study like a CT scan. This cannot be further from the truth. In fact diagnostic testing in my opinion is almost the least important part of making a diagnosis.

I cringe when my colleagues order tests before even examining the patient. In my opinion this can be misleading and adds unnecessary cost and time to the patient often with very little added information.

For example while on rounds earlier today I was asked to see a patient that was admitted with a fever. After a brief interview and a physical examination I concluded that she had a pyelonephritis, an infection of her kidney. I went on to tell her that I planned to give her an antibiotic and some fluids. She and her family then asked if I was going to perform any tests. When I replied that none were further needed unless she did not respond as expected, they were taken aback. I explained that the clinical history and physical examination was clear enough to make the diagnosis in this young otherwise healthy lady. Appropriate treatment was started and her fever did as predicted abate and she felt better the following morning. Later the following day she was discharged feeling much better.

So how did I arrive at the diagnosis without ordering any tests? The same way doctors have done for hundreds of years by using their knowledge of medicine. When I was a medical student my professor would say “Take a detailed history the diagnosis will come to you”.

So what is the first step in making a diagnosis? The first step is to understand the chief complaint. The chief complaint is the main reason the patient decided to come to the doctor. “My side hurts” or “I have a headache” are simple examples of a chief complaint. Just this simple one sentence with the age and sex of the patient will narrow the diagnosis considerably. My side hurts in a young woman above would narrow the diagnosis to an abdominal problem.

The next step is the history of the complaint. When did it start? What other features are present with it? Is it getting better or worse? Is the patient losing weight unexpectedly? Was there any recent travel? Any fever? Chills? Diarrhea? These may be some of the other features that can accompany the chief complaint “My side hurts” This will further narrow down the possibilities of the diagnosis. In the above patient she had a fever of 104F with chills and shivering without any diarrhea. Already we have been able to narrow the diagnosis to most likely a kidney infection. Unfortunately this is the part that most busy physicians spend the least amount of time with and often patients are least willing to participate in. I cannot tell you the number of times I have been told by patients or their family members to “Just look at the tests that the other doc ordered” or  “I have already told the ER doc all this, why are you asking me this again?” I always get a detailed history on my own, like most other things in life the devil is in the details.

Think about your symptoms not about the diagnosis

Further information on past medical problems, surgeries, pregnancies and medications are now looked at.

By the time I have taken the history I often am at least 80% certain of the diagnosis. Now comes the physical examination.

A physical examination is the part where the doctor will methodically examine every organ system of the body for clues of the disease process including the vital signs. Already having a fair idea of the diagnosis the astute physician can further strengthen or refute the possibility of a diagnosis. By the time I have finished my physical examination I can often by over 90% sure of the diagnosis or have a very short list of the possibilities.

Mind you we still have not ordered any tests. In fact most medical school training is spent to understand what is normal and what is not. After all one cannot be expected to recognize something as abnormal if they do not know what normal is. A very small proportion of medical school training is on actual “tests”.

Back to our case; on examination she is shivering, appears dehydrated and has a rapid pulse rate, all indicating infection. Her abdomen is soft and without tenderness. This was important to exclude any other abdominal diagnosis that would have been a reasonable alternative diagnosis. In fact she did have a tender right flank that further added the likelihood that she is suffering from a kidney infection.

So without ordering a single test I am over 90% certain

So without ordering a single test I am over 90% certain that she has a right sided kidney infection as a result of which she is also dehydrated. She should respond to antibiotics and fluids. Which she did.

Her chief complaint was the flank pain and her diagnosis was kidney infection.

Does she need any further testing? In this case not at this time.

Am I advocating no testing? Not at all. A test is just that, a test. A challenge to see which way to proceed. But one must first have a destination. First have a reasonable set of diagnosis after a thorough history and physical examination then order the test that will be most helpful in breaking the stale mate. That is the best use of resources.

Most diagnosis can be made without any tests, some even without even touching the patient. Very often misguided testing produces unexpected inconsequential findings that have nothing to do with the original complaint which often leads to more testing and so on.

The most notorious test that I encounter in my day to day practice is where a patient goes to his healthcare provider with a fever and a throat strep test is ordered without examining the throat. This can be positive even without strep throat. Which unfortunately as soon as it is positive the further search for the diagnosis comes to a grinding halt. Practitioners please do not swab non inflamed throats!

So how does one get the most out the doctors visit, but clearly stating the reason for the visit, the complaint is a very important reason for the visit. Do not try to analyze and arrive at the diagnosis yourself. Also be ready to give the duration of the illness and any other associated symptoms that may go with it. All this will help make an accurate diagnosis minimize diagnostics and expedite treatment.

Remember be wary of the doctor who orders tests before even asking what the problem is.

Leave a Reply