All Nurse Practitioners have experienced patients presenting with vague symptoms. Knowing what questions to ask and what tests to order are key to eliminating potential diagnoses until you find the right one. In this article, we will cover the various steps of the differential diagnosis process and how Nurse Practitioners can build comprehensive and efficient potential diagnosis lists.
Related: Laboratory Diagnosis: Challenging Case Studies
What is a differential diagnosis?
A differential diagnosis is formulated anytime a patient presents with symptoms that can fit multiple conditions. Differential diagnosis is the foundation for ruling out similar conditions until you finally arrive at the correct diagnosis. Differential diagnosis is essential to prevent overlooking a serious condition and to ensure the patient starts the correct treatment plan.
What are the steps of a differential diagnosis?
When a patient presents with a complaint, the first step is to formulate a list of all potential causes of that symptom. Then, perform a comprehensive assessment, including symptom analysis, history, and physical examination designed to help support or refute all potential diagnoses. Next, create a list of all the potential causes of the symptoms and order tests to rule out or confirm these causes. Finally, review test results and decide on a treatment plan for your patient.
What are the facets of a comprehensive symptoms analysis?
Begin by assessing the patient’s symptoms and ensuring you understand the full context. It is essential to ask patients the right questions to get a complete picture of the presenting symptom. A symptoms analysis must include:
- Location on the body, including radiation
- Quality: dull, sharp, etc.
- Severity on a pain scale
- Timing: onset, duration, and frequency
- Setting where it occurs
- Aggravating factors
- Relieving factors
- Associated manifestations
How patient history collection aids in differential diagnosis
Next, review the patient’s medical history, including prior injuries, surgeries, social history, medication history, allergies and family history which may be related to the current complaint. Be sure to ask your patient if they have previously experienced these symptoms, recently started a new medication, or know anyone in their family with similar symptoms.
It is also important to gather information about the patient’s lifestyle. This includes diet, exercise, sleep, stress levels, and changes in interpersonal relationships. For certain symptoms, you may also ask about recent trips, outdoor excursions, and physical activities.
Gathering all this information will give you a better idea of potential causes for their complaint. For example, if you know your patient presenting with GI trouble recently traveled to a country with poor access to clean water, you might test for certain bacterial infections before worrying about Irritable Bowel Syndrome or another disease.
How to perform a physical examination for a differential diagnosis
The physical examination is a powerful tool for assessing a patient’s condition and gathering key data. Physical examinations can include a mix of observation, palpitation, auscultation, and percussion.
When evaluating for a differential diagnosis, the physical examination will focus on those diagnoses supported by the chief complaint and history of present illness. Through the physical examination, Nurse Practitioners can get more information that either supports or refutes a potential diagnosis. This feedback can help refine your theories and justify prioritizing one potential diagnosis over another.
For example, say the patient presents with a generalized skin rash. Nurse Practitioners may feel challenged by diagnosing a skin rash due to the number of potential conditions that can cause a rash and the many different presentations of rash a condition can cause. After questioning the patient about itchiness and pain and checking about new medicines, outdoor exposures, and potential allergens, a physical examination may be most helpful for determining the correct diagnosis.
You should consider what parts of the body the rash covers and how it appears. Is the skin dry or greasy? Are there discreet bumps or large swathes of irritation? Do you see pustules in hair follicles? Are there targets, lines, or lesions? Understanding the key elements of a condition’s presentation will help you know what to look for in a focused physical examination.
Related: Grand Rounds for the AGACNP Diagnostic Reasoning for the Adult-Gerontology Acute Care Nurse
How can Nurse Practitioners generate an inclusive differential diagnosis list?
Once you understand the patient’s symptom history, you can compile a list of potential diagnoses. Prioritizing life-threatening conditions over less severe ones is an important first step in differential diagnosis. Also, prioritize conditions with elevated risks due to your patient’s comorbid conditions.
Next, rank potential diagnoses by how common they are: in general, in your geographical area, and for your patient’s population. Start with common conditions, then uncommon, then rare ones until you have a comprehensive list of all potential causes for the patient’s complaint.
How to maximize diagnostic testing to rule out potential diagnoses
The next step of the differential diagnosis is to order tests for potential diagnoses. This might include lab tests like blood tests or urinalysis; imagining such as X-ray, MRI, or Ultrasound; or biopsy.
Because testing can be extremely costly and potentially invasive, it is important to order tests strategically. Many dermatologic conditions can be diagnosed via clinical examination. When diagnostic testing is necessary, begin with basic tests and move on to more elaborate testing only when necessary. Additionally, start with the most likely diagnosis, which may be the most common condition, and move down the list from there.
Finally, if the patient’s symptoms match any serious, urgent, or potentially life-threatening conditions, it is important to do testing to rule out such conditions, or even immediately refer to a higher level of care when necessary. Even if the likelihood is small, Nurse Practitioners should never count a serious condition out of the differential diagnosis until the proper testing rules it out.
Reviewing results and choosing a treatment plan
Once you have the test results back, you will hopefully have a better understanding of what condition is ailing your patient. Build a treatment plan based on a positive test result. See if the treatment alleviates the symptoms.
What do you do when a differential diagnosis fails?
If you complete a differential diagnosis and still have multiple potential conditions, what’s the next step? Maybe the tests were inconclusive, the initial treatment plan did not work, or new symptoms arose.
As a Nurse Practitioner, you have three options: you can order more tests, send the patient to a specialist, or start a treatment plan. While you may have a preferred next step, it is important to discuss these options with your patient. For example, many patients have GI upset from certain antibiotics and may choose to wait for treatment until further testing is done to ensure they start the right medication.
If you and your patient decide to move forward with a treatment plan despite an inconclusive diagnosis, how do you choose the correct treatment? The best treatment will depend on what remains on your potential diagnoses list. It may be best to start with a low-impact or short-lasting treatment to see if you are headed in the right direction.
Alternatively, you may prescribe a stronger and more widely beneficial medication that treats numerous conditions. For example, many bacterial infections are typically treated with a specific medication but can also be eliminated with penicillin or a cephalosporin antibiotic.
Differential diagnosis is a challenging skill that takes time and practice to master Nurse Practitioners. Taking each step one at a time will help you work efficiently to arrive at the correct diagnosis.
Earn CE hours by enrolling in our Clinical Challenges in Primary Care online course (free with Passport Membership)!
