How to Develop a Differential Diagnosis

You and your colleagues have been asked to work together to create a differential diagnosis for Mr. Frank McGrath, prioritize your diagnoses, and propose tests that will help you confirm the first diagnosis in your differential.

For this task, you should begin by gathering information on Mr. McGrath's signs and symptoms from the patient interview video and the email from your attending physician. Then you should research what those signs and symptoms mean. Your research will help you create a differential diagnosis, and a plan for testing the first item in the differential. Finally, together with your team, you need to write a paper that includes:

• An explanation of your differential diagnosis, including your rationale for that differential.
  
  
• A proposal for which tests you would like to use to confirm or disconfirm the first diagnosis in your differential and an explanation of what the tests will tell you.

The steps below will walk you through this process.

1. Meet with your team and pick a team leader.
   
   Contact your mentor with questions about your team assignment.
   
   
• You may want to review the General Skills Resources link in the left menu for information on successfully forming a team.
  
  
2. Review the email from Dr. Jordan Casey. It may be helpful to print the email and highlight the important points.
   
   
3. Download the Clinical Findings Research Notes Template attached to Dr. Casey's email. This template will help you organize your notes.
   
   
   1. You will not need to submit this document. Use it to organize the information you will use to make your differential diagnosis.
      
      
   2. Each team member should download a copy of the template and keep his/her own notes. Each of you may notice different things, which you should share with each other and discuss.
      
      
   3. When you feel ready to learn how to develop a diagnosis, download and review the Develop a Diagnosis and Treatment Process document.
      
      
      1. This document is a reference that outlines the complete process of diagnosing and treating a patient.
         
         
      2. You may not want to look at this until after you've seen the patient video once or twice and taken notes on your observations. Or you may want a sense of where you are going now. Read this document whenever you wish. You may refer back to it at various points in your work.
         
         
      3. Pay special attention to Steps 1, 2 and 3. They are the steps you will work on in this task.
         
         
4. Gather clinical findings. Clinical findings are signs, symptoms, and test results, all of which give you information to help you make a diagnosis.
   
   
   1. Watch the patient interview video.
      
      
      1. As you watch the video notice any signs you see in the patient. How does he look? What are the outwardly visible indicators that he has a medical problem?
         
         
      • The video may not show enough of his physical state to judge, but the doctor describes how he looks. Consider the doctor's description.
        
        
   2. You should also pay attention to the patient's symptoms (the things he tells you he is experiencing). How does he feel? What's bothering him? What brought him into the clinic today?
      
      
   2. Read the email again and note any other clinical findings described in it.
      
      
   3. Write down each sign and symptom in the first column of the Clinical Findings Research Notes Template.
      
      
5. Develop and prioritize a differential diagnosis
   
   1. Using the Diagnosis and Treatment Archive (DATA), research each clinical finding you have identified and formulate a differential diagnosis about what is wrong with Mr. McGrath.
      
      
      1. Look up each sign, symptom, and test result you learned about from Mr. McGrath's exam. Read about what they each mean and what problems (diagnoses) might be causing them. As you research each clinical finding, take notes in column two of the Clinical Findings Research Notes Template. Write down anything that will help you understand each clinical finding.
         
         
      2. Then look up the possible causes/diagnoses to see what various signs and symptoms are commonly found with the given illness. See if the signs and symptoms of the diagnosis seem to describe what Mr. McGrath is experiencing. Write down these causes in the third column of the template.
         
         
      3. As you come across diagnoses that look like they describe Mr. McGrath's condition, look up how you would test for that illness/diagnosis, and what result you would need to see to confirm it.
         
         
      4. Make a list, using the template you downloaded, of the diagnoses that seem possible and the tests you need to do to confirm or disconfirm them.
         
         
         1. This list is your differential diagnosis, but you need to prioritize it, putting the most likely or most life-threatening diagnosis at the top of the list, and the least likely at the bottom.
            
            
         2. It is possible you might have one diagnosis that seems most comprehensive and reasonable. If that happens, it is fine. However you will need to include a few alternative diagnoses to fall back on if your tested diagnosis comes up negative (meaning the patient doesn't have that illness).
            
            
6. Determine appropriate tests. As you consider various diagnoses or causes of the various clinical findings, you should research how to test to confirm or disconfirm your suspected diagnoses. Track the test names and how they are relevant in column 4 of your Clinical Findings Research Notes Template.
   
   
7. Review the Tips and Traps by clicking the link at the top of this page. Carefully read each suggestion and make sure you are on the right track.
   
   
8. Write your plan to test the first diagnosis in your differential.
   
   
   1. Download the Diagnostic Report Template from Dr. Casey's email. You should use this as an outline when writing your report.
      
      
   2. Using the notes from your Clinical Findings Research Notes Template, create a report in Microsoft Word. This document should contain:
      
      
      1. Your differential diagnosis (the prioritized list of diagnoses you are considering) with a rationale for the list (why you are considering each possible diagnosis, and why you ordered each diagnosis the way you did).
         
         
      2. The test(s) you want to run to confirm or disconfirm your highest prioritized diagnosis, and why (what you will learn from the result).
         
         
   3. For writing help, refer to the General Skills Resources link in the left menu.
      
      
9. Review your work.
   
   1. Did you develop a list of possible diagnoses based on Mr. McGrath's symptoms?
      
      
   2. Did you prioritize them according to the most likely or life-threatening to the least likely or life-threatening?
      
      
   3. Have you identified tests that will confirm or disconfirm the first diagnosis in your prioritized differential, and defended the need for those tests?
      
      
10. Submit your work.
    
    Review the checklist located in the Submit Your Work section of this task and submit the assignment to your mentor.
    

Getting Started

1. Work with your team and decide how you will approach this assignment. Create a work plan that shows how you will divide up your work. It is important to have a plan of attack!
   
   
2. Review all the materials thoroughly before you start writing your report (i.e., emails, video, step-by-step instructions, templates, resources, etc.). Make sure you understand what you are being asked to do. If you have questions, you should contact your mentor.
   

Gathering Clinical Findings

1. Some signs might be the same as the symptoms. If your patient tells you about something you can see, write it down as a sign. You don't need to list it more than once.
   
   
2. The patient's history can be as important as his signs and symptoms. Listen carefully when he describes his background. Think about the impact his history may have on his current condition.
   

Using DATA

1. When you are working in the Diagnosis and Treatment Archive (DATA), you may find that the clinical findings are not listed exactly as you noted them from the patient examination. Look for entries on the Clinical Findings list that are close to what you have written on your Clinical Findings Research Notes Template. You may need to be creative and think about different ways to say the same thing: e.g., a bruise may also be called a skin discoloration.
   
   
2. When you are using the DATA, some of the links might present information written in fairly advanced language. Don't be discouraged if you have trouble understanding it right away. Work slowly. Discuss the information with your group. It may even help you to read the material out loud. If you and your team cannot understand something that you believe may be important, feel free to contact your mentor for support.
   

Developing a Differential Diagnosis

1. You should develop a differential diagnosis by looking for common denominators in the "Possible Cause" column of your Clinical Findings Research Notes Template. For example, if through your research you learn that every sign or symptom you have identified can be caused by a heart problem, then a heart problem should be one of the diagnoses in your differential, and perhaps it should be given a high priority.
   
   
2. If a diagnosis explains only one of the patient's signs or symptoms but does not explain the others, try to find a diagnosis that explains more than one, and if possible, all of them.

A patient may have multiple conditions at one time causing several unrelated signs and symptoms. When that is the case, each problem requires its own treatment. Often, though, if a patient complains of multiple signs and symptoms at one time, there is one cause/diagnosis that results in numerous signs and symptoms.

For example, not drinking enough water can be the cause of a person feeling hungry, tired, and dizzy (all symptoms of dehydration). By treating the root of the problem rather than each individual symptom, you can eliminate further complications.

3. Your differential diagnosis may include only one primary diagnosis that seems to explain all of the signs and symptoms you have observed in this patient. That's fine; you will need to include a few alternative diagnoses to fall back on if your tested diagnosis comes up negative (meaning the patient doesn't have that illness).

Checking Your Work

1. If you determine that a diagnosis in your differential is highly likely, you may be tempted to go a step further and try to determine the cause of that problem. You are not being asked to do that in this task. You will get a chance to look at those causes, but for now, focus on explaining the symptoms.
   
   
2. When you recommend a test for a diagnosis, make sure to provide a rationale for how it will help you to confirm or disconfirm the diagnosis. What will it tell you about the organ or organ-system you think may be causing the patient's problematic signs and symptoms?
   

Diagnosis and Treatment Archive (DATA) - Internal Medicine

Diagnosis and Treatment Process
This document describes the process that health care professionals typically use to diagnose and treat their patients.

Lasix Overview
This link provides an overview of Lasix, including its use and possible side effects.

Ask the Expert

What is a differential diagnosis?

What is an example of a differential diagnosis?