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 Step-By-Step Guide
Tips and Traps
Resources
Step-By-Step Guide
How to Critique a Differential Diagnosis
As the next step in your case review, you have been asked to do a critique of Dr. Chang's differential diagnosis. It is your job to evaluate whether Dr. Chang created an appropriate list and whether he used the correct reasoning.
To create a differential diagnosis, a physician needs to look closely at all of the information s/he collected during the interview and exam. At this stage, though still gathering data, the physician starts to analyze and interpret all of these facts. The physician starts to ask: what does all of this add up to? What is actually wrong with this patient? The physician makes a list of possible diagnoses and prioritizes them (i.e., decides which are most likely and which are least likely). With this differential diagnosis in mind, the physician can then test his/her hypotheses in an organized way, in an effort to narrow down the list.
Use the step-by-step instructions that follow to critique Dr. Chang's differential diagnosis and her rationale (or reasons) behind it.
Getting Started
- Get prepared to do your work in this task. Go to the email sent to you by your mentor and download the attachments. You will need the following throughout the task:
- Differential Diagnosis Form- This form lists the diagnoses that Dr. Chang thought might apply to Jenny Anderson, in order of priority. Dr. Chang noted the evidence she found for and against each diagnosis and gave her rationale for each placement she made on the differential.
- Critique Template of the Differential Diagnosis- This is the form that physicians at Lakeshore Hospital use to critique a fellow physician's differential diagnosis; it contains questions for the reviewer to answer about each of the physician's choices.
- In addition, you'll need to refer back to Task 1 materials, particularly the video and physician's notes in the Patient Interview and Examination Form, because a physician's differential is based on the data collected during the initial interview and exam. You will also need to reference your own assessment of Dr. Chang's notes, to carry through any mistakes you believe she may have made in the first steps of this case.
- Carefully review the email from Dr. Mendoza to become familiar with the goals of this task.
- Read through the Differential Diagnosis Form and the Critique Template of the Differential Diagnosis to familiarize yourself with the contents of each.
- For now, don't be concerned if many of the diagnoses on the list seem unfamiliar to you; you will become familiar with them as the task progresses.
- Work with your teammates to create a quick list of the major questions that you have about how physicians create a differential diagnosis; they should be questions that you would like answered as you complete this task. These questions might help you focus your thought process in this task.
- Read about the process physicians use to develop a differential diagnosis.
- It is a good idea to take notes on any material you find that answers the questions you raised, that you find especially interesting or enlightening, or that you believe may help you to critique Dr. Chang's differential.
- Read the second and third sections of Diagnosis and Treatment Process document, which cover the steps a physician takes when developing a differential diagnosis. These sections also includes a link that gives a clear definition of a differential diagnosis.
- Also explore the resources related to Developing a Differential Diagnosis in the Resources (above).
- For additional guidelines that physicians follow, see the Tips and Traps (above).
- Organize your team to do the critique.
- If you need a refresher on getting organized, refer to the step-by-step guide for Task 1.
Completing the Critique Template
Follow the steps below to fill out the critique template for each diagnosis in Dr. Chang's differential.
- Make a list of all of the significant findings for Jenny Anderson.
- Significant findings encompass anything abnormal, including:
- symptoms noted by Jenny and her mother
- signs Dr. Chang observed in the physical examination
- information from any early tests or lab reports (if available)
You will use this information to compare the list of findings for Jenny's case to the list of typical findings for each possible diagnosis.
- Review the patient's record in order to localize (or pinpoint the location) of these findings anatomically.
In order to determine what structures may have been injured, ask yourself the following questions:
- In which areas were pain and other abnormalities found?
- What functions or movements were affected?
- What structures control these movements?
- How do these structures (e.g. muscles or joints) work in a normally functioning person? If necessary, research the structures in the Resources (above) or in other materials you find.
- Why might the functioning of these structures be impaired or otherwise changed in this patient?
- In localizing the findings, try to get as specific as the data will allow but no more so. For example, you may only be able to pinpoint the body region of a patient (e.g., the back) or you may be able to identify the exact structure involved (e.g. left trapezius muscle). To describe the patient's problem to a very specific level, it may necessary to do further testing, so don't jump too far ahead if your evidence isn't conclusive.
- Review the list with your teammates when you are finished. As a group, come to a consensus on the final list before moving on to the next step. In the upcoming steps, you will be matching this list against diagnoses that can produce the signs and symptoms you have identified.
- Do some research about the diagnoses that Dr. Miller hypothesized (or thought could be possible) for this patient.
Please note: If when you organized the team you decided to “divide and conquer” the research of the diagnoses, it is important for you to meet with your teammates at the end of the research period to share the information each person found. By the time you are finished with this step, everyone needs to have a basic familiarity with each diagnosis.
- In order to critique the possible diagnoses in Dr. Miller's differential for Jenny Anderson, you'll need to be familiar with what a typical presentation of each condition looks like. You'll need to know:
- typical signs and symptoms
- risk factors
- the kinds of motions or actions that typically cause the injury (also known as “mechanism of injury”)
- Some resources that you may find helpful include:
- Diagnosis and Treatment Archive (DATA) - DATA contains lists of signs, symptoms, risk factors, and tests for each diagnosis; you can use this information to explore Jenny's condition in a systematic way. This can be found in the Resources (above).
- Web resources- You can find additional reading with facts about each diagnosis in the websites listed in the Resources (above). You can also use web resources that you find in your own searches.
- Print resources – If available, school and public libraries may have many resources you can draw upon as supplements, such as library books about sports medicine and sports injuries, anatomy books, or encyclopedias.
- Fill in the third column of the critique template ("Do you agree with the physician's decision to include this condition...?"). Indicate whether you agree with Dr. Chang's decision to include or exclude each condition from the differential diagnosis, and explain your reasons. To determine whether you agree or disagree, consider the following for each diagnosis:
- Is there a match between the significant findings for the patient and the typical presentation for this injury?
- The summary list for Jenny Anderson that you created in Step 1 can help you with this analysis. With this list in hand, go back to DATA (Diagnosis and Treatment Archive) and to your research notes/materials for each diagnosis, and note each sign, symptom, or risk factor Jenny has that is typical of the injury.
- Pay attention to the timing of the symptoms for this patient. When was the onset (or start) of the symptoms and how quickly did they develop? Symptoms that develop acutely over 24 hours might suggest a different problem than the same symptoms that develop over 2 or 3 months.
- Pay attention to the location of the symptoms for this patient, which you considered in Step 1 of these instructions. Now match this information against each diagnosis. Is there evidence that the patient may have injured the relevant structure(s) for that diagnosis?
- Does the patient fall into a group with a high (or low) statistical likelihood for experiencing this injury?
- Look back at the patient's demographic information, lifestyle, and other risk factors and compare it with what you've found in your research for the injury.
- Review the information on risk factors for each diagnosis in both the DATA (Diagnosis and Treatment Archive) and in the websites related to each diagnosis in the Resources section.
- Was the patient's story consistent with the mechanism of injury for this condition?
- Since certain motions, actions, or events will cause particular kinds of injuries, it's often helpful to compare the patient's story with the typical one for this injury. Review the typical mechanism of injury for each diagnosis.
- If you can identify how the patient's injury occurred and what abnormal motion or action took place at the time of the injury, if any, you can use this information to narrow down the differential.
- Were there any significant positive or negative results from early tests?
- If you find these results sufficiently convincing, you can base a decision to include or rule out a diagnosis on the test result(s).
- Fill in the fourth column of the critique template (“Do you agree with its ranking…?”). Indicate whether you agree with Dr. Chang's ranking for each diagnosis, and explain why or why not.
- Start by asking yourself which items you think should be ranked high, which low, and which in-between. See if you agree with Dr. Chang's general choice for each diagnosis. Note where you have disagreement – if you think a particular item was ranked or ruled in or out incorrectly.
- Within each grouping, make further distinctions, comparing the high-likelihood diagnoses with each other, and so on.
- In order to decide how each item should be ranked, revisit the questions in step 3 (above). In step 3, you decided whether the answers to those questions were sufficient to include the diagnosis in the differential. Now, you can compare two diagnoses at a time with regard to the answers to those questions. Use the information to decide which one seems more likely for Jenny.
- Fill in the fifth column of the critique template (“Do you agree with the physician's rationale…?”). Indicate whether, in your opinion, Dr. Chang used the right strategies to make a decision about the diagnosis.
- Review the factor(s) that Dr. Chang gave the most weight in making each decision. (These are found in the Rationale column in the Differential Diagnosis Form.)
- Identify the factors she identified for each diagnosis, such as:
- matching the patient's findings against the typical findings
- considering statistical likelihood for this patient
- considering whether the mechanism of injury for the patient is consistent with the diagnosis
- considering significant results from tests
- any other strategies that you, your teammates, or your mentor may identify
- Ask yourself some questions about the factors Dr. Chang noted:
- Were the factors that she noted relevant?
- Did she weigh each factor appropriately?
- Were there any findings that she did not use that she should have identified?
Meeting to Exchange Feedback
- Meet with your cohort (made up of all teams participating in the rotation) to discuss your findings and ideas. You will be assigned one or more sections of the critique form at the beginning of the meeting; your team will present your key ideas and lead the discussion of that section with the cohort.
- After incorporating any feedback you may have received during the cohort discussion, submit your work to your mentor. Be sure to save all of your work, regardless of whether you submit it to the mentor.
Tips and Traps
How to Develop a Differential Diagnosis
- Physicians do not build hypotheses on very general signs and symptoms that are associated with numerous conditions. Instead, they use the more unique findings in a patient's case as the basis for identifying potential diagnoses. For instance, pain and swelling can indicate a large number of orthopaedic (and other) conditions. While physicians would certainly take these symptoms into account as indicating a problem, they would not use them as the basis for creating a differential. Instead, physicians would look for more diagnostically relevant signs and symptoms that would help them to identify specific conditions.
- Physicians do try to figure out what processes are taking place in the body to cause the signs and symptoms. For example, the patient's signs and symptoms may signify that there is an inflammatory process taking place in response to an injury or an immune response to a virus or bacterium. Physicians make inferences about what the signs and symptoms suggest is going on in the body.
- Physicians do pay attention to the absence of certain symptoms or to negative findings in the physical examination or lab reports, when these will be helpful in making a diagnosis. For example, a patient who responds normally to the Thompson test (by plantarflexing the foot) cannot have a ruptured Achilles tendon.
- Physicians do eliminate or lower the ranking of conditions that couldn't be responsible for some of the patient's key symptoms. For example, nonallergenic rhinitis might be listed as a possible diagnosis causing a patient's stuffy nose, but if the patient also has very itchy eyes, a symptom usually associated with allergies but not with nonallergenic rhinitis, this diagnosis is either lowered in priority or removed completely.
- Physicians do consider the likelihood of seeing a given condition in a patient of a certain age, gender, lifestyle, etc. They give more weight to conditions that are more likely to be seen in a certain population and move them higher on the list.
- In general, physicians do rank common conditions ahead of rare ones with similar symptoms. Many medical students learn the old saying, “When you hear hoofbeats, look for horses, not zebras.”
- Physicians do not always accept the information stated by a patient at face value. While the information gathered from a patient is often valuable, it can be imperfect; patients can forget or misremember the facts of their illness or injury. Sometimes, patients can bias their reports (of pain severity or of their symptoms from a chronic or recurring condition) for personal reasons; for example, a competitive athlete may downplay a condition in order to continue participating in the sport. Physicians keep these possibilities in mind and do not rely on this information to be 100% reliable or complete as they creates the differential.
- Physicians do understand the capabilities and limitations of various tests and lab information, especially in the early stages of a condition. Some tests are only helpful in diagnosis after a certain amount of time has passed. Certain injuries may be hard to see on X-rays, especially in particular views. Physicians are aware of all of this as they create the differential.
- Overall, physicians do approach the differential diagnosis by keeping an open mind and being as thorough and careful as possible.
Meeting to Exchange Feedback
- Do back up the points you make with your research and with strong, logical arguments.
- Do be open to hearing disagreement or different ideas from other teams. If your points generate some debate, then you know you have done your job well and hit upon an interesting issue. Both your team and other teams can learn from the discussion.
- Do listen carefully to the thoughts the other teams are sharing, and note if they are the same or different from your own. Remember that there is not necessarily a “right” answer that all physicians would agree with. Different physicians use different approaches.
- Do jot down notes to record what you learn in the discussion. You may also note down any questions you still have about creating a differential diagnosis. You will return to the topic of differential diagnosis in other cases in this rotation.
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Diagnosis and Treatment Archive - Sports Medicine
What is a differential diagnosis?