Diagnostic Process Flashcards
what are the components of the diagnostic process
- information gathering
- integration and interpretation
- hypothesis
- gather more information
symptom
a manifestation of a disease as reported by the patient
sign
a manifestation of disease that the clinician observes
what is premature closure?
failing to consider reasonable alternatives after an initial diagnosis is made
evidence definition re: probabilities
information that helps you update your estimate probabilities
what is a disease illness script?
a representation of a condition in the mind of a practitioner
varies between practitioners
what are the components of a disease illness script
- epidemiology
- time course
- clinical presentation/syndrome
- mechanism or pathophysiology
syndrome definition
a set of signs and symptoms
what is included in epidemiology?
things that increase your risk
- demographics: age, sex, race, ethnicity, socioeconomic status
- risk factors or pre-existing conditions
- exposures (travel, hobbies, occupation, hobbies, drugs sexual, medications, pets)
what is included in time course?
duration and pattern (aka. persistence)
what is meant by duration?
duration can be: hyperacute, acute, subacute, or chronic
what is meant by pattern/persistence?
constant or episodic
what are some words that would describe a constant pattern?
stable, progressive
ex. something constantly getting worse
what are some words that would describe an episodic pattern?
waxing and waning (comes and goes); intermittent
what is included in clinical presentation aspect of a disease illness script?
the most important signs and symptoms
can use “classic” presentation but it can be misleading/lead to stereotyping
what are some features of high quality disease illness scripts?
- uses medical terminology and categories - it helps you to make better diagnostic decisions because you can categorize things appropriately
- they will change over time with experience and research
- multiple disease illness scripts can be compared/contrasted
does someone have to have all the signs and symptoms listed on a disease illness script to be considered for that condition?
no
problem representation definition
a representation of what’s going on with the patient that you want to match as closely as you can with a disease illness script
why is good problem representation important?
- you will have a more effective and precise diagnostic process if you have good problem representation
- also helps with researching possible treatments
steps to process patient information into a problem representation
create a problem list
process the list (emphasize the most valuable evidence and de-emphasize less valuable evidence; abstract patient concerns into medical terminology; process the list ie. put it into medical terms)
patient illness script definition
a concise representation of the patient’s concern that allows matching with a disease illness script
what are the components of a patient illness script?
- epidemiology
- time course
- clinical presentation (syndrome/signs/symptoms)
- other important medical history
how does a patient illness script differ from a SOAP note?
patient illness script won’t differentiate between subjective and objective but kind of combines them together
what is excluded in the clinical presentation aspect of a patient illness script?
- elements already mentioned in previous sections
- findings of little relevance
- past medical history that is unconnected to the chief complaint
- previous diagnosis - UNLESS they were clearly correct
differential diagnosis definintion
the process by which clinicians consider some possible causes of the patient’s signs and symptoms before making a final diagnosis
why is it important to come up with a differential diagnosis list?
if not done deliberately, people tend to fail to consider options after arriving at an initial guess
what is the availability heuristic?
the tendency to use information that comes to mind quickly and easily. It favours recent or more memorable experiences
are initial guesses or later guesses more subject to the availability heuristic?
initial guesses
why can we not make a list of all the possibilities instead of going through the differential diagnosis process?
- this is called possibilism
- technically impossible to do this as we are limited by our medical knowledge and time
- can lead to unnecessary testing/diagnostic work up
- people sometimes use mnemonics for generating differentials but they lead to very long lists
what is an emergent condition?
a condition that is an emergency,
it is NOT something that is emerging
what are the factors that we should consider when looking to make a differential diagnosis list?
probability - what is most likely
prognosis - which conditions are worse if left unconsidered
pragmatism - what conditions have the best benefit:harm ratio if treated
when do we start considering differential diagnoses?
generally after we are done gathering a bit of information about the chief concern
probability definition
how likely something is
how is probability expressed?
on a scale of 0-100% or 0-1 where 1=100%
is it possible to reach a probability of 100%?
No, we can never be completely certain
is it possible to reach a probability of 0%?
No, we can never be completely certain
are practitioners more likely to over estimate or under estimate probability of diagnosis before and after testing? what types of bias are present here? implications of this?
- they are likely to overestimate probability of diagnosis both before and after testing
- cognitive bias: base rate neglect, anchoring bias, confirmation bias
- implications: over testing, excessive medication and procedures
representativeness definition
the degree to which something is representative of, or similar to, the stereotype
when we are asked to judge probability, what do we often judge instead?
representativeness - whether someone fits into a certain category
T/F: an uncommon presentation of a common disease is more likely than a common presentation of a rare disease
true: if this weren’t so, diagnosis might be a matter of pattern-matching. we should think of the thing that is more common, not as much of the thing that matches the most
base rate definition
the base rate of a disease or a statistic that there is a certain ratio of something (ex 20:1 male farmers:male librarians in North America)
pretest probability
the best estimate of a disease probability before you do a test;
serves as a starting place from which to update probability
how to determine pretest probability
want to start with a good/best reference class
best reference class definition
the set of patients that most closely matches the patient at hand
reference classes that can be used as pretest probabilities
- prevalence of disease in a population
- studies that give eventual diagnosis in patients presenting with the complaints similar to your patients (this would be more specific than prevalence, less common/hard to find)
what should you NOT use as a reference class for pretest probability? why?
- incidence in the population because it’s the frequency fo a disease over a period of time
- lifetime prevalence - its the chance of developing the disease over a lifetime and will be an overestimate for pretest probability
likelihood ratio (LR) definition
a measurement of evidence strength
numbers that represent the value of the information a test provides
what does an LR of 1 mean?
it is useless because it does not change the probability
what does an LR >1 mean?
greater LRs increase the probability by more
what does an LR <1 mean?
LRs < 1 decrease the probability (they can go all the way down to zero)
what does an LR of 0 mean?
LR of zero tells us we can definitively rule out a condition
can you have an LR < 0?
No
Is a change is probability linear with the size of the LR?
No, there are diminishing returns
ie. if the LR doubles, it doesn’t mean that the probability will also double
what probability will have the most effect on what the post-test probability will be? Why?
the pre-test probability because the more extreme your initial probability (closer to 0 or 100%), the harder it should be to change your mind
what % probability is the most uncertain you can get?
50% certainty. Any lower and you’re more certain that the condition is not present
what is meant by “good” tests and “bad” tests?
tests can’t really be described as good or bad. A good test may mean it has valuable information if it’s positive, negative, or both but usually a test is only particularly good at ruling in or ruling out a condition and not both.
when do we look at the LR+ value?
when the finding is present
when do we look at the LR- value?
when the finding is absent
what is the equation for calculating LR+?
LR+ = sensitivity/ (1-specificity)
what is the equation for calculating LR-?
LR- = (1-sensitivity)/specificity
what is the SpPIN/SnNOUT mnemonic telling us?
a Specific test, if Positive, helps rule the condition IN
a Sensitive test, if Negative, helps rule the condition OUT
what should you do if you can’t find an LR?
you should be conservative with your estimates about a test’s value because people tend to overestimate the “diagnosticicity” of their evidence
diagnostic odds ratio definition
a ratio of likelihood ratios, calculdated by LR+/LR-
gives an overall measurement of a test’s performance
what can we use a diagnostic odds ratio for?
we cannot use it the same was as we use LRs but it gives an overall measurement of a test’s performance
what do they call LRs outside of medicine?
Bayes factor from Bayesian probability
what are some examples of double-counting evidence (findings that are closely correlated or included in other findings)
- increased patellar reflex and increased ankle jerk reflex (when one increases, the other also increases)
- getting 4/5 ABCDE score for melanoma and irregular borders since these would both be present if the other was present, we couldn’t count this as 2 pieces of evidence
sensitivity definition
in patients who have the disease, the probability that the test will be positive
specificity definition
in patients who don’t have the disease, the probability that the test will be negative
T/F: specificity is the same as the top part of the LR (probability that you would see some evidence if your hypothesis were true)
false: sensitivity is the same as the top part of the LR
what is the least reliable method of getting a LR value?
estimating
rule of thumb for rough calculation of probabilities for moderate pre-test probabilities (close to 50%)
know the table for moderate pretest probabilities:
LR 10 +45%
LR 5 +30%
LR 2 +15%
LR 1 0% change in probability
LR 0.5 -15%
LR 0.2 -30%
LR 0.1 -45%
rule of thumb for rough calculation of low pre-test probabilities and moderate LRs
multiply the probability by the LR to get a good estimate
ex. a pretest probability of 2% with and LR of 5 applied results in a post-test probability of 10%
negative predictive value definition
probability that the disease is absent given that a test was negative
positive predictive value
probability that the disease is present given that a test was positive
what assumption is made with NPV and PPV
we assume that your patient’s pretest probability is the same as those in the study that was used to deterine the PPV and NPV
are using PPV and NPV more or less accurate compared to applying LRs?
they are not as accurate as applying LRs, depending on the pretest probability
pathognomic findings definition
are pathognomic findings more sensitive or specific?
findings that, if present, strongly increases the probability of a condition
they are highly specific, not necessarily sensitive
would a pathognomic finding have a high LR+ or low LR-?
high LR+
Sine qua non findings definition
findings which, if absent, strongly decreases the probability of a condition
would a sine qua non finding have a high LR+ or low LR-?
low LR-
close to zero
testing threshold definition
the probability below which you would no longer gather diagnostic information explicitly about a condition because you will have sufficiently ruled it out;
above this probability, you would need to do more testing
treatment threshold definition
the probability above which you believe a particular treatment is warranted
if you are between the testing threshold and treatment threshold, what should you do?
do further testing - more questions, physical exams, labs, other diagnostic workups
if you are below the testing threshold, what should you do?
nothing, the probability was not high enough to warrant testing
if you are above the treatment threshold, what should you do?
you should treat with the specific treatment for which you’ve set the threshold
what factors determine the testing threshold?
- severity of the condition
- harms and accuracy of available tests
what factors determine the treatment threshold?
- the degree to which it’s safe to go without treatment
- harms and accuracy of further testing
- harms and benefits of treatment
you should not set the testing threshold below the ___
population prevalence
- this would suggest that you think someone taken at random from the population is in the testing zone, not just someone who is symptomatic
what is the management threshold?
the treat zone is sometimes called the management threshold because this is where you will figure out if the condition needs to be managed/treated
what is a working diagnosis?
the diagnosis that you are actually treating
will the treatment threshold for all conditions be the same?
no, some will be higher and some will be lower
what types of conditions do patients not often think of when asked about their medical problems? what can we do to offset this?
chronic illnesses because they may not realize the significance or relevance of the chronic diseases. We can ask questions in a way that patients understand what we are asking
why is the history component of patient interviewing important?
- approximately 80% of medical diagnoses can be made with history alone
- relatively low cost, low harm, with possibly high information return
what do you need to get out of history-taking?
you need sufficient info to complete a patient illness script and ideally, to cross a threshold (test or treatment threshold)
what is the CC?
chief complaint/chief concern
the patient’s reason for the visit
what is the HPI and how is it related to the CC
HPI = history of the present illness
it is how we explore the patient’s CC
what is sometimes included in history-taking?
Review of Systems
what does SOCRATES stand for?
Site
Onset
Character
Radiation
Associated Symptoms
Timing/change over time
Exacerbating or relieving factors
Severity (0-10)
what does OLD CARTS stand for?
Onset
Location
Duration
Character
Aggravating factors
Relieving factors
Timing
Severity
what does OPQRSTUV stand for?
Onset
Provocation
Quality
Radiation and region
Severity
Timing
Understanding
Values
as part of history-taking, what are the components of Other Medical History? (SMASH FM)
Social history
Medical history
Allergies
Surgeries
Hospitalizations
Family History
Medications
what are the components we would inquire about as part of taking a social history? (FED-TACOS)
Food/diet
Exercise
Drugs
Tobacco
Alcohol
Caffeine
Occupation/hobbies
Sexual
what is the ICE mnemonic used for?
Ideas about their diagnosis
Concerns about elements discussed
Expectations for the visit and including treatment
what is the Review of Systems?
askign questions ordered by body system
breadth of questioning is somewhat arbitrary
what is the review of systems NOT used for? why?
screening, otherwise it may lead to overdiagnosis, instead use a targeted approach
what is the purpose of medical interviewing?
to gather information, to establish a safe atmosphere/trust with the patient, and to provide patient education
what is problem-oriented interviewing?
it is simply gathering information about a problem
how does the biomedical approach differ from the biopsychosocial approach in medicine?
biomedical approach focuses on just biological factors leading to limited understanding
biopsychosocial approach connects biological factors with psychological and social and allows for increased understanding of illness and health
patients often seek care due to their ___ and not their ___
experience; symptoms
what is the rationale for medical interviewing? (3 components)
- patients often seek care for their experience of their symptoms affecting their ability to do things in their life
- they often have more than one concern
- being able to tell one’s symptom story is therapeutic and diagnostically useful
how does patient-centered interviewing differ from clinician-centered interviewing?
- patient centered involves patient leading interaction, allows them to express importance and describe their experience of the disease, uses open ended questioning and builds and maintains the clinician-patient relationship
- clinician centered has clinician leading interaction, is biased by clinician’s beliefs and priorities, interviewing is to elicit symptoms of disease, uses more closed-ended questions, and differentiates potential conditions patient may be suffering from
are using open-ended questions more of a patient-centered or clinician-centered interviewing skill?
patient-centered
what are the 2 categories of open-ended questions?
focusing and non-focusing
what are non-focusing questions? what are some examples of this?
things that don’t give any indications where you want the patient to go
ex. silence, nonverbal encouragement, continuers
what are focusing questions? what are some examples of this
they let the patient know you want to know more about what they said
ex. echoing, requesting, summarizing
are closed-ended data gathering skills more of a patient-centered or a clinician-centered interviewing skill?
clinician-centered
what are some examples of closed-ended data gathering skills/questions?
- questions that produce Yes/No answers
- questions that produce brief replies
- multiple choice questions
what are the different types of emotion-seeking skills?
direct inquiry and indirect inquiry
what is an example of a direct inquiry in patient interviewing
how did that make you feel?
what is an example of an indirect inquiry in patient interviewing
- inquiring about the impact
- eliciting beliefs or attributions
- intuiting how the patient might be feeling
- asking about triggers
what is the NURS mnemonic used for?
conveying empathy skills
Name the feeling or emotion
Understand the statement
Respect
Support
what are the steps, in order, of an integrated medical interview?
- opening interview - set the stage
- elicit CC and set agenda
- open HPI
- learn patient experience of illness
- transition to middle of interview
- HPI
- past medical history
- psychosocial history
- family history
- ROS
- end of interview
overdiagnosis definition
involves making people into patients unnecessarily
what components are involved in overdiagnosis?
overdetection and overdefinition
what is the main result of overdiagnosis?
diagnosis causes more harms than benefits and can trigger a cascade of over-treatment
overdetection definition
identifying problems that were never going to cause harm
overdefinition definition
medicinizing ordinary life experiences through expanded definitions of disease
components of overdetection
finding abnormalities that are any of the following:
- were never going to cause harm
- do not progress
- progress too slowly to cause symptoms or harm during a person’s remaining lifetime
what are some causes of overdetection?
- increased use of high-resolution imaging causes us to see incidentalomas
- self-testing
- certain screening programs
what is an incidentaloma?
surprise abnormalities unrelated to the original reason for doing the test
what is one recognized risk of excessive CT imaging?
surgical overtreatment
how does overdefinition happen?
- lowering threshold for a risk factor without evidence that it helps people live better or longer
- expanding disease definitions to include people with ambiguous or mild symptoms
what is one of the downsides of having so many different methods of diagnosis?
we see overdefinition result because a lot of normal conditions are thought of as pathological
what is a misleading consequence of overdefinition?
Will Rogers phenomenon: healthy people are included in disease population, making it appear that the new definition of disease helps people with the disease
overselling/disease mongering definition
categorizing unpleasant experiences most people have from time to time as diseases
harms of overdiagnosis
- treatments offer little (if any) benefit for lower risk patients, while harms remain the same
- psychological and behavioural effect of labelling
- adverse consequences of subsequent testing and follow up
- misinformation spreads so that people who have been overdiagnosed encourage others to get screened for a condition
higher rates of suicide in men within a year of prostate cancer diagnosis is an example of ___
one of the harms of labelling due to overdiagnosis
what % of thyroid cancer cases in Canada are estimated to be overdignosis? how do we know this?
75% because there has been a rise in diagnosis without a decrease in mortality
__ lab tests can contribute to overdiangosis
unvalidated lab tests
how do unvalidated lab tests contribute to overdiagnosis?
tests may give results that reflect something going on in the patient’s body that may not have any significant relationship with disease
what questions should we ask about lab tests to make sure that they are valid?
sensitivity and specificity
T/F: a plausible mechanism is an appropriate justification for a test to be considered valid
false: a plausible mechanism is NOT an appropriate justification for a test to be considered valid
screening definition
testing asymptomatic people
(via questions, physical exams, labs, etc.)
what are some examples of periodic screenings that are done?
colonoscopies
gynecological exams
mammograms
PSA
what value does a screening test provide?
the ability to rule out a disease in healthy people
what is the potential benefit of screening?
- detect diseases that are better treated before signs and symptoms show up and prevent people from suffering with/dying from them
what are the important factors for a DISEASE to be considered for screening
the disease should be:
- a significant public health concern (common or significant morbidity/mortality)
- treatable within these stipulations - the potential for cure increases with earlier detection; treatment is easily available
what are the important factors for a TEST to be considered for screening
the test should:
- be sensitive to PRE-clinical disease
- be safe
- be inexpensive
- be easily accessible/available
- lead to demonstrated improved health outcomes
pseudodisease definition
a condition detected by screening that does not require treatment because it will not adversely affect patient life;
if treated, patient may be considered “cured” despite the fact that even if untreated, the condition would not have killed them before they died of something else
what are the 2 types of pseudodisease? describe them. what are some examples of each type?
type 1 - conditions that might not progress to symptomatic disease and may even regress (ex. ductal carcinoma in situ)
type 2 - slowly progressive disease/conditions with a long detectable preclinical disease (ex. prostate cancer often is slow growing) - patient would die with it, not from it
is the pretest probability for a screening test very high or very low? why?
very low because the screening applies to otherwise healthy people
why is mammography a cliche screening test?
because doctors aren’t able to accurately assess post-test probability - pre-test probability is usually very low so the post-test probability is about 20% if positive and 0.7% if negative. therefore there is a very low likelihood that there is breast cancer
describe the harms of screening
- harms of tests: radiation, perforation from colonoscopy, cost, time
- false positive: psychological burden, over testing/further testing, over treatment financial burden, etc.
is screening for thyroid cancer useful? why or why not?
it is not because the potential for cure did not increase with early detection and testing did not lead to improved health outcomes
is it necessary to perform pap tests in women <25 yo? why or why not?
because at least 10% of women at this age have abnormal test results and the lesions would likely go away on their own
is it necessary to screen for PSA? how often does overdiagnosis of prostate cancer occur?
it is not often necessary to screen for PSA
one study found that 21-50% of cancers detected by screening were considered overdiagnoses
are general health checks/yearly physicals helpful clinically as a screening test?
no. overall, they do not reduce morbidity or mortality; plus they see increased new diagnoses and more people with self-reported chronic conditions
