Diagnosing Disease: Definition, Process & Steps

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

The process of diagnosis disease in patients involves several steps that allow a doctor or healthcare professional to collect information. In this lesson we'll walk through those steps to help you understand how a diagnosis is made.

What is a Diagnosis?

When you don't feel well you see a doctor because they are a trained medical professional who can diagnose why you are sick. The diagnosis is the identification of a disease, disorder, or other condition that you may have that is causing your symptoms.

Diagnoses are sometimes very easy to come by, while others may be a bit trickier. In order to make a good diagnosis your doctor will go through a process that involves several steps, allowing them to gather as much information as possible. Let's discuss the steps of that process so that you have a better idea of how a diagnosis is made. Ready to get started?

Step 1: The Medical History

The first thing your doctor will do when you come to the office is get your complete medical history. This involves collecting information about any past and current symptoms, any diseases that your family members may have, and collecting any other information that may be helpful such as medications you may be taking. You might think that lab tests and other diagnostic tools are more important than your medical history, but they can carry important clues the doctor might need.

The doctor will also to you about how you are feeling, how long you have been feeling that way, and any external influences that may be factors. This gives your doctor a good foundation from which to move forward.

Step 2: The Physical Exam

After talking with your doctor, they will want to examine you physically. This includes collecting your vital signs like your blood pressure, pulse, and temperature. These measurements can provide a lot of information to your doctor. Your doctor may also listen to your lungs and heart with a stethoscope, feel or palpate parts of your body like your lymph nodes and abdomen, test your reflexes, use percussion or tapping to listen to sounds in your body, look at your eyes, ears, and mouth, and examine any other places they think may be important.

Collecting your vital signs, such as blood pressure, pulse, and temperature can help aid in forming a diagnosis.
collecting vital signs

This physical exam allows the doctor to see, feel, and test your body to find out what is abnormal and what hurts (if you are experiencing pain). It's important to let your doctor know where you are experiencing symptoms so that they can more closely examine those parts of your body and collect more information for their diagnosis.

Step 3: Performing Diagnostic Tests

The next step in the diagnostic process is to run some tests. Usually by this step your doctor already has a good idea of what the diagnosis is and the tests are run simply to confirm this diagnosis. Other times though, your doctor may not be quite sure and the tests are used to rule out certain diagnoses to narrow down the field of possible options.

Your doctor may order an MRI, which is an imaging test to aid in forming a diagnosis.
MRI with patient

What kind of tests will your doctor run? It depends entirely on your symptoms and the suspected diagnosis. Your doctor may order bloodwork that will tell them how different organs are functioning, or imaging tests like a magnetic resonance imaging (MRI) scan, X-ray, ultrasound, or computed tomography (CT) scan to look inside your body. Respiratory tests, exercise tests, or any number of other diagnostic tools can also be used to provide information.

Step 4: Drawing Conclusions

It's time to put it all together to form the official diagnosis. Again, sometimes this is fairly straightforward while other times it may require a few runs through the diagnostic process.

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