The Approach to the Medical Diagnosis for
Nurse Practitioners:
A Review of the
Nursing Diagnostic Process and the
Medical Diagnostic Process
and how they differ
Objectives
This module has been designed to help the
Student NP to understand the thinking
processes behind the development of a nursing
diagnosis and the development of a medical
diagnosis.
Upon completion the Student NP will be able to
describe the key differences between the two
processes and understand the appropriate
application of each within NP practice.
Outline
This module will:
• Review the steps of the Nursing Process and its link to the cognitive
processes of developing a nursing diagnosis
• Review the cognitive processes of developing a medical diagnosis
• Compare the two processes
• Give examples of each process
• Show why the nursing diagnostic process should not be used to
make a medical diagnosis
• Provide a detailed “walk-through” of the medical diagnostic process
• Make statements regarding the appropriate use of each process in
NP Practice
The Nursing Process has five stages
Assessment
Diagnosis
Planning
Implementation
Evaluation
The Nursing Diagnostic Process
The Nursing Diagnostic Process follows the Nursing
Process. It begins with an assessment and works
towards a diagnosis.
▫ The nurse collects all data from the holistic assessment
(subjective and objective), detects patterns and
regularities, confirms the pattern with additional data
and comes to a conclusion (diagnosis) about the
patient.
Pattern recognition is used to distinguish normal from
abnormal patterns
It looks like this:
•
•
•
•
An observation is made
Obtain subjective and objective data
a pattern is recognized and a hypothesis is made
More information is gathered to confirm the
hypothesis
• The pattern is confirmed = Diagnosis
Metaphor:
I search for as
many puzzle pieces as possible.
I begin to see a pattern emerge.
I gather more pieces to allow
me to confirm the pattern is true.
The pattern is the Diagnosis.
The Medical Diagnostic Process
• The medical diagnosis begins with identifying
the chief complaint or symptom.
• The practitioner takes into account some key points
about the patient and the context: usually age and gender. This
gives the practitioner a context for the chief complaint.
(Nurses do this, too.)
• The practitioner comes up with about 3-5 ideas about the etiology
of the chief complaint in consideration of the context of the
patient.
• These 3-5 ideas make up the differential diagnoses.
• In a sense, the diagnosis comes first. However, it is just a
hypothesis at this point and not a conclusion.
• Note that Data Collection is only very preliminary at this point.
Medical Diagnosis cont.
Working from a differential list
• After compiling a differential diagnosis list, the
practitioner begins to gather subjective and objective
data and, as he/she does so, the practitioner works to
gather data to support or refute the 3-5 differentials.
The practitioner is testing the hypothesis that one of
these diagnoses may be correct.
• The practitioner is able to do this by having a good
understanding of the typical signs and symptoms of each
possible diagnosis, and knowing what is common and
uncommon for this patient’s demographics and risk
factors. (Pattern recognition)
It looks like this:
•The green icon is the chief
complaint.
•The four hearts represent the DDx
•The squares below the hearts are
the data points that support that
particular DDx.
•The diagnosis favours the yellow
heart hypothesis, and the orange
heart hypothesis must also be kept
in mind.
Metaphor:
It is a matching game where I match data pieces to pre-determined patterns .
The biggest collection of matching pieces “wins.”
An Example of the Medical Diagnostic Process
• A chief complaint of unilateral ear pain in an
otherwise healthy adult could be:
 Eustachian tube dysfunction (inner ear
congestion),
 Acute Otitis Media,
 URTI
 Cerumen impaction.
These are the differential diagnoses for a
complaint of unilateral ear pain in the healthy adult.
Subjective data:
With the differential in mind, the practitioner will ask about:
• Diving, air travel, trauma, recent URTI, fever, dizziness,
nausea, hearing loss, drainage from ear, ringing in the ear,
headache. Has he ever had this before? Does he have any
allergies.
[ Notice how each of these is a characteristic of one of the
differential diagnoses and not “every possible” item of data.
It is a focused data collection based on the Differential.]
Findings: This patient denies all of these except for some
hearing loss in that ear that has gradually worsened. He has
had this before; ear was “plugged with ear wax.” He has a
history of hay fever and environmental sensitivities that
cause rhinitis and sneezing. He works as an accountant.
The Evolution of the Differential Diagnosis (DDx)
At this point, the DDx looks like this:





Eustachian tube dysfunction –Possible (2˚to allergy)
Acute Otitis Media –unlikely without URTI
URTI -ruled out*
Cerumen impaction -Possible
Gradual onset hearing loss - Acoustic Neuroma?*
*During the process data collection, some DDx may be
removed entirely, some may be added due to new
findings, and some will be weakly positive and others
strongly positive
Continuing the Data Collection,
Working From The Differential List
Objective Data:
• On examination, the patient is found to have cerumen
impaction in the affected ear canal. His neurological exam,
in regards to the acoustic neuroma, is negative. He has no
signs or symptoms of a URTI and no cervical adenopathy.
• The differential now looks like this:
 Eustachian tube dysfunction – unlikely
 Acute Otitis Media -ruled out
 Cerumen impaction -positive
 Acoustic neuroma – unlikely but
important to rule out.
Arriving at a Diagnosis
The diagnosis can now be stated:
Dx: Cerumen impaction – unilateral, Rt.
DDX: acoustic neuroma with unilateral hearing loss,
eustation tube dysfunction.
• The practitioner can commence with a treatment plan based
on the working diagnosis (keeping the DDX in mind)
Action: The impacted cerumen is removed with irrigation and
curretage. The patient states he can hear normally now and
the pain is almost gone. The TM is normal. (Reassessment)
• The diagnosis is confirmed: Cerumen impaction.
Comparing the Two Processes:
A Review
The Nursing Diagnostic Process
-is like gathering as many pieces of a puzzle as possible
and then arranging them into a pattern.
The pattern identified is the diagnosis
 The strength of this model is that it works well for nursing diagnoses
especially those that concern the whole person rather than the
disease itself.
 The weakness of this model is that it may stop before the underlying
etiology is found, and it may not take in to account other possibilities.
 It uses high-level critical thinking, reason and cognitive skills but not
the scientific method of hypothesis-testing.
The Medical Diagnostic Process
Starts by having only one piece of a puzzle, and recognizing that
that piece could be part of several possible etiologies or pictures.
More puzzle pieces are gathered and matched according to the pictures
under consideration.
In the end, the pattern with the most matching pieces is the diagnosis.
The weight of evidence will usually
favour one hypothesis which then becomes the diagnosis
 The strength of this process is that all findings must be accounted for
and remaining differentials are kept in mind even when the final
diagnosis is made. It has this feature as a safeguard in case the first
diagnosis is, in fact, wrong.
 This also allows for symptoms of red flag conditions to be ruled out or
in to avoid catastrophe.
 The main weakness is that it is disease-oriented and is not the best
method to approach personal and lifestyle issues.
Key differences
• While pattern recognition, high level reasoning,
critical thinking and hypothesizing are utilized in both
processes;
The medical diagnostic process uses data to compare
the best fit of sign or symptoms to hypothesized predetermined patterns. The pattern most heavily weighted
by the evidence is the diagnosis. This is a deductive
process;
The nursing diagnostic process sums up data pieces into
a pattern that can be confirmed by additional data. The
pattern is confirmed and becomes the diagnosis. This is
an inductive process.
Another example
Nursing diagnosis of a medical issue*:
Assessment: Urine output is dropping.
The nurse will gather more information by conducting a
through head to toe assessment including vital signs, patient
subjective experiences, colour and warmth of skin, sources of
fluid loss, and history of intake, IV patency, knowledge about
the patients current illness/condition.
The nurse discovers that the patient is not eating or drinking
well.
The nurse investigates why the patient is not eating/drinking
and finds that the patient is nauseated.
Nursing Dx: Decreased urine output secondary to nausea as
evidenced by decreased oral intake.
*to illustrate that nursing models and medical models have unique uses and should not replace each other.
Medical Diagnosis, same issue:
Chief complaint: The urine output has dropped.
Context: situation, age, comorbidities, history
Differential diagnosis: dehydration, renal failure, decreased
intake, increased output elsewhere. r/o hemorrhage and
shock.*
Data collected: Subjective: nausea; Objective: vital signs,
peripheral perfusion, examination for sources of fluid
loss/third spacing, Diagnostic tests: urine specific gravity,
labs including CBC, lytes, BUN and Cr, stool for OB.
*Note again how the data collection is
connected to the differential diagnoses.
It is not a random or general collection of data.
Another example
A patient comes in complaining of fatigue. The physical
exam is negative. Lab reports (CBC and low ferritin) come
back showing anemia.
Nursing diagnosis: Fatigue secondary to anemia as
evidenced by hgb of 80. Likely due to insufficient iron
intake as evidenced by low ferritin.
Medical diagnosis: fatigue and anemia
DDX: hypothyroidism, chronic blood loss,
pregnancy, iron-deficiency anemia.
The nursing diagnosis may not adequately consider the
many underlying causes of the anemia or lead one to
consider serious diseases like cancer. The nursing
diagnosis is still useful because it will lead to diet teaching
regarding iron-rich foods which is still an appropriate
nursing interventions.
Let’s walk through another example of
the Medical Diagnostic Process.
The chief complaint is a cough.
You know that the patient is a 18 months old boy. His
immunizations are up to date, and the child has no
allergies or chronic conditions. It is winter. His older
brother has a cold.
What do you do next?
Construct a differential list.
What are the top 5 differentials* in this case?
1) URTI
2) RSV Bronchioloitis
3) Asthma
4) GERD
5) Foreign body aspiration
* Your list may be slightly different. That’s okay.
Now what?
1) Collect subjective and objective data to rule in or rule out
your potential diagnoses.
2) Assess the HEENT and chest and cardiac systems in this
process.
3)But what are you looking for?
Think about your differential list.
▫
▫
▫
▫
▫
1) URTI
2) RSV Bronchiolitis
3) Asthma
4) GERD
5) Foreign body aspiration
What are the disease patterns and symptoms and
signs of each differential you are considering?
• You know the symptoms of an URTI.
• You know the pattern of RSV: runny nose, mild fever, cough, low O2
saturations, fine crackles bilaterally to chest. The cough is loose.
• You know the pattern of Asthma: cough occurs when the airways are
50% constricted. It is often preceded by a URTI. The expiratory
phase may be longer than normal. The cough may be dry or
congested and can be paroxysmal. The cough is worse at night.
• You know that GERD often presents with cough when supine and
after meals. They may have had a lot of post-feeding regurgitation
as a smaller infant.
• You know that a sudden onset of cough and sometimes an
inspiratory wheeze (stridor) are hallmarks of a foreign body
aspiration.
Your data collection finds the following
subjective findings:
The history:
• Has had a runny nose ++ for three or four days.
• Had a flu immunization one month ago.
• Has not been eating very well and drinking poorly
• Coughing day and night for 2 days; came on gradually
and getting worse.
• Had a mild fever on day 1.
• Doesn’t want to lay down.
• Sometimes a little blue around the lips.
• No regurg history as a smaller baby.
Refine your differential as you go
along: What is your differential now?
• RSV bronchiolitis – possible: Rhinitis, mild fever, cough,
mild cyanosis reported
• Asthma – possible, started with URTI symptoms,
paroxysmal cough, mild cyanosis reported
• GERD – unlikely, pattern not typical of GERD.
• URTI – possible, has cold symptoms and cough and mild
fever
• Foreign body – ruled out for now: slow onset cough and
URTI symptoms.
Your physical exam finds:
•
•
•
•
T 37.5, HR 148, RR 48 and moderately laboured
O2 saturation 87%, slight peri-oral cyanosis.
Hands and feet cool with cap refill 4 seconds.
Chest has fine crackles bilaterally to entire posterior
chest and RML. No wheezes or stridor heard. Expiratory
phase normal.
• Clear profuse rhinitis.
• Prefers to sit on mother’s lap.
• Decreased energy.
What is your medical diagnosis?
1) RSV – Positive, all symptoms fit, time of year matches
2) Asthma – Unlikely: negative Hx of RAD
3) URTI – unlikely: viral URTI symptoms but breath
sounds and hypoxia do not fit
4) GERD – rule out, child ill
5) Foreign body aspiration –ruled out
6) Bacterial pneumonia – positive findings: hypoxia, resp
distress, unwell. Negative findings: pathologic breath
sounds are bilateral and classic for RSV.
Diagnosis: RSV bronchioloitis, hypoxia, dehydration
DDX: bacterial pneumonia (supra-infection of viral RTI)
Conclusion
• Nursing and medical diagnostic processes differ.
• Both processes are valuable.
• Nursing diagnostic processes are excellent for
patient-oriented, holistic care issues, and for
guiding nursing care in all settings.
• Medical diagnostic processes are efficient and
effective for making medical diagnoses.
• There is some overlap but one is not a substitute
for the other; each has their unique purpose.
Bibliography
Baerheim A. (2001). The diagnostic process in general practice: has it a twophase structure? Family Practice, 18(3), 243–245. Retrieved from
http://fampra.oxfordjournals.org/content/18/3/243.full
Dunphy, L., Winland-Brown, J., Porter, B. & Thomas, D. (2007). Primary
care: The art and science of advanced practice nursing (2nd ed.).
Philadelphia: F.A. Davis Company.
Godron, M. (1976). Nursing diagnoses and the diagnostic process. American
Journal of Nursing, 76(8), 1298-1300. Retrieved from
http://www.jstor.org/stable/3424002
Richardson, W., Wilson, M. & Guyatt, G. (2002). The process of diagnosis.
Users’ Guides to the Medical Literature. Retrieved from
http://medicine.ucsf.edu/education/resed/articles/jama6_the_process.pdf
Robinson, D. (2002). Clinical decision making: A case study approach (2nd
ed.). Philadelphia: Lippincott.
Trochim, W. (2002). Research methods knowledge base: Deduction &
induction. Retrieved from
http://www.socialresearchmethods.net/kb/dedind.php
Athabasca University
Centre for Nursing and Health Studies
MN:NP Program
Author Donna Clare MN NP
Jan 2012