DDx Flashcards
DDx
Differential diagnosis is a systematic process used to identify the proper diagnosis from a set of possible competing diagnoses.
A differential diagnosis is a list of possible conditions or diseases that could be causing the patient’s symptoms. It’s based off of the facts obtained from the patient’s symptoms, medical history, basic laboratory results, and a physical examination.
It is a method of analysis of the patient’s history and physical exam to arrive at the correct diagnosis.
DDx is a process of weighing the probability of one disease vs. that of other diseases causing a patient’s illness.
learning how to identify a medical dx
As part of this process, review items such as:
Your patient’s current symptoms
Health history
Results from a physical examination
confirming a dx
The PCP will make a list of the most likely conditions or diseases that may be causing your symptoms. This is the differential diagnosis.
Prioritize your list differential diagnoses
It enables you to rule out possibilities and confirm a final diagnosis.
Critical thinking
Process by which the information is gleaned from the history and physical examination:
Merged with clinical knowledge, experience, and the current best evidence
Formulate the next steps in patient care -Development of the diagnostic and management plans
Critical reflection = Clinical reasoning
Critical reflection involves thinking through the reasoning for these decisions
The clinical examination
Thus far, we have been concerned with the initial interaction with the patient:
Establishment of respectful rapport
Information gathering processes -History and physical examination
Next steps:
Organizing
Integrating
Analyzing inform
Assessment, judgement, and evidence
Bringing the decision making, clinical experience, and knowledge of the patient together with the current best evidence regarding the issues involved
Assess information.
Assign priorities.
Form clinical opinion.
Reflect on own biases.
Integrate patient and professional preferences.
Assess further
Problem identification
Problem is anything that will need further evaluation and/or attention.
May be related to:
-Uncertain diagnosis
-New findings related to a previous diagnosis
-New findings of unknown etiology
-Unusual findings revealed in the clinical examination/laboratory tests
-Personal, social, or emotional difficulties
Formulate problems as specifically as possible.
The problem list is key to developing a complete understanding of a patient’s concern
Review the list and note the absence of findings that you might expect in support of your hypotheses. -Beware of “red herrings,” the bits of information that are distracting and draw your thinking away from central issues.
Critically evaluate unexpected or unusual findings, but do not let them distort full consideration of all you have learned
After a match between the data (both subjective and objective) and a presumed diagnosis is made -Consider the appropriate laboratory or radiologic studies to confirm the diagnosis.
-Specialty consultation may be needed before laboratory or radiologic testing and establishing the diagnosis. -Helps focus your investigation
Valid Hypotheses
Clinical reasoning allows you to consider and discard a variety of possible diagnoses—from the common to the rare.
There are at least three diagnoses for every disease (Kopp, 1997):
-The one that unifies what you have learned
-The one you cannot afford to miss
-The one that it actually is
Do not have tunnel vision or jump to conclusions during the interview.
Occam’s razor or lex parsimoniae (“law of parsimony” or “law of succinctness”)
-All findings should be unified into one diagnosis.
-This is not always true.
-More than one disease process can exist at one time in the same person.
Possible Barriers to Clinical Reasoning
Feelings, attitudes, and values can impair decision making.
Know yourself and take time for personal reflection.
Critical reflection involves thinking through the reasoning for these decisions.
The Ethical Context
Ethics does not provide answers.
Consideration of ethical principles provides the framework for respectful, flexible discussion and a disciplined approach to decision making.
For a given problem, consider:
-Autonomy
-Beneficence
-Nonmaleficence
-Utilitarianism
-Fairness and justice
-Deontologic imperatives
Mechanism and Probabilism
Mechanistic (deterministic) thinking is governed by a sense that knowledge must be certain and not subject to attributes of the observer.
Our decision making must have a balance between mechanism and probabilism (certainty in knowledge is impossible).
Do not be dominated by the mechanistic assumption that there is a precise and discoverable cause for every event.
Validity of the Clinical Examination
Great majority of diagnoses can be achieved with the information from a competent history and clinical examination.
Limit the indiscriminate use of expensive technology.
Keep in mind:
-Sensitivity
-Specificity
-True positive and true negative
-False positive and false negative
-Positive predictive value and negative predictive value
Bayes Theorem
Likelihood of your diagnosis being related to your findings depends on:
-Probability of those findings being associated with that diagnosis
-Prevalence of both that particular diagnosis and that combination of findings in the community in which you are serving
Evidence-Based Practice
Evidence-based practice (EBP) is a system that incorporates the best available scientific evidence into clinical decision making, in the care of the individual patient.
EBP balances the strength of the evidence, the risks and benefits of treatment (including lack of treatment), and diagnostic tests, while integrating clinical expertise.
Evaluation and Management Plan
You decide what you think is going on (the diagnosis) and what you are going to do about it (the management plan).
You and your patient arrive at a jointly considered approach involving:
-Laboratory and imaging studies
-Subspecialty consultation
-Medications, equipment, assistive technology
-Special care
-Diet and activity modification
-Follow-up visit
-Patient education
Setting priorities
Ask yourself these questions:
What is the patient’s physical condition?
Is something going on that overrides every other consideration and needs immediate attention?
Are there abnormal laboratory values or imaging findings that need immediate attention?
What is the patient’s social circumstance?
Will a job be threatened if there is an absence from work?
Are there small children at home for whom no other caretaker is available?
Is there available and convenient transportation to and from services and care?
What is the patient’s economic circumstance?
Does the patient have adequate health insurance coverage?
Is the cost of care or medication going to compromise other areas of the patient’s life?
Patient’s subsequent behavior is a major variable in health status or therapy. -Medication adherence
The patient must be actively and positively involved if an optimal outcome is to be achieved.
Stages of Behavioral Change
Precontemplation
Not yet admitting there is a problem
Contemplation
Admitting that there is a problem but not yet ready or sure of wanting to make a change
Preparation
Intending to take action in the immediate future, beginning to take small steps toward change
Action
Changing behavior, overt modification in behavior
Maintenance
Being able to sustain action and working to prevent relapse
Termination
No temptation/confidence in not returning to old behavior
Relapse
Shift from action or maintenance to an earlier stage (precontemplation or contemplation)
Considering appropriate use of resources with concern for the greater good of the larger community is known as:
Beneficence
Nonmalficence
Utilitarianism
Fairness
Ans: C
Rationale: Utilitarianism is the showing concern for the greater good of the larger community.
The ability of an observation to identify correctly those who do not have the disease is:
Sensitivity
True positive
Specificity
True negative
ANS: C
Rationale: Specificity is the ability of an observation to identify correctly those who do not have the disease.
A problem may be defined as:
Anything that will need further evaluation and/or attention
The chief concern that the patient tells you when they come in for a visit
Developed from the review of systems
Absence of findings that denote health or well-being
ANS: A
Rationale: A problem may be defined as anything that will need further evaluation and/or attention. It may be related to one of the following: an uncertain diagnosis, new findings related to a previous diagnosis, new findings of unknown etiology, or personal or social difficulties.
5 steps to ddx
Acquired data: use all available sources
Identify key features: both pos and neg finding. May be from hx, exam, labs, other tests, or chart review
Create prob representation: use semantic qualifiers. Synthesize related findings into clinical syndromes
Adopt a framework: may be anatomic, physiologic, or other. Commonly adapted from a reference source.
Apply key features to the framework: this generates the ddx
Pt hx
Acquire Data
CC/ HPI
Past History
Social History
Family History
Allergies
Identify key factors
Physical Exam
Labs, Diagnostic tests, treatments, consults
Results/ Findings
Create a problem rep
Use semantic qualifiers:
“Qualitive abstractions of the signs & symptoms of a case which is implied or explicit
“Over the past several month, both legs have been getting weaker and weaker”
CHRONIC, PROGRESSIVE BILATERL LOWER EXTREMITY WEAKNESS
Synthesize related findings into clinical syndromes
A constellation of clearly related findings should be grouped into a single clinical syndrome, if possible.
Confusion, T 39.0, HR 120, BP 130/90, RR 24, WBC 16.2, Cr 2.4, positive blood cultures
SEVERE SEPSIS
Caution: this is the clinical syndrome not the diagnosis!
Adopt a framework
Anatomic
Lungs, heart, kidneys, etc …
Physiologic
Neurologic, pulmonary, renal
Others
Environmental, psychological
Apply Key Factors into a Framework
Generating a Differential Diagnosis
Make a list of pertinent key factors from
Patient’s history
Physical exam
Diagnostic and lab results
Additional info
Examples of Differential Diagnosis
The DDx of may look like this:
Patient complains of headache ( cc/HPI, H&P)
Meningitis, stroke, stress/tension are common causes
Patient complains of SOB. ( cc/HPI, H&P)
Heart failure, asthma, pneumonia are common causes
Patient complains of chest pain. ( cc/HPI, H&P)
MI, GERD, pericarditis are common causes
Provisional Diagnosis
The most likely diagnosis of the differential diagnosis list based on the criteria and findings
A provisional diagnosis denotes it is not 100% sure of a diagnosis
More information is needed
Primary Diagnosis
The diagnosis that is decided and found to be identified health problem.
Used for healthcare billing purposes
ICD-10 codes (examples)
-Pneumonia due to Streptococcus pneumoniae J13
-Inguinal hernia K40
-Malignant neoplasm of the central portion of the breast C50.2
