U2 PCCR - clinical reasoning

clinical reasoning

process used by practitioners to plan, direct, perform, and reflect on client care

the cognitive process clinicians use to gather data, interpret findings, generate hypotheses, and arrive at a diagnosis or management plan

differential diagnosis list

a list of possible causes for the patient's signs or for an abnormal finding

working diagnosis

the one diagnosis from a differential list used to base the patient's treatment plan

prevalence

fraction of a population having a specific disease at a given time

incidence

the number or rate of new cases of a particular condition during a specific time

sensitivity

percentage of patients who have a true positive

they have the disease

true positive = yes to disease

high sensitivity = low change of false negative

specificity

percent of patients who have a true negative/are disease free

high specificity = low chance of a false positive

pretest probability

probability that a disease is present before further testing is done

test threshold

probability below which the diagnosis is so unlikely you exclude it without requiring further testing

treatment threshold

probability above which the diagnosis is so likely you treat the patient without further testing

posttest probability

when a test is so helpful it pushes you past one of the thresholds

validity

measures if the test accurately identify whether a patient has a disease

positive predictive value,

probability that a person with a positive test has the disease

negative predictive value

probability that a person with a negative test does not have the disease

true negative

patient with a negative test does not have a disease

false negative

patient with a negative test does have a disease

true positive

patient with a positive test does have a disease

false positive

patient with a positive test does not have a disease

likelihood ratio

likelihood that a given test result would occur in a patient with the disease compared with the likelihood that the same result would occur in a patient without the disease

tells you how much a test result changes the pretest disease probability to the posttest disease probability

the magnitude of the LR indicates how strongly a specific test will raise (rule in) or lower (rule out) the likelihood of disease

two clinical reasoning systems

System 1: Intuitive

-operates quickly and often automatically via mental shortcuts

-rapid and intuitive -> habitual response systems -> challenging to alter

-used by experts most of the time

System 2: Hypothetico-Deductive (Rational)

-explicit analytical approach via deliberate and controlled thought process

-employs logic and probability to reach conclusions

-requires more time and cognitive effort

anchoring bias

a tendency to fixate on initial information from the patient that influences the diagnosis

tendency to lock onto salient features in the pt's initial presentation too early in the diagnostic process, and fail to adjust diagnosis later

availability heuristic

assumption that a diagnosis is more likely/frequent if it readily comes to mind

confirmation bias

seeking supportive evidence for a diagnosis at the exclusion of more persuasive information refuting it

diagnostic momentum

prioritizing a diagnosis made by prior clinicals, discounting evidence of altenative explanation

framing effect

interpretation of information that is influenced by the way the info is framed/presented

representation error

failure to take prevalence into account when estimating the probability of a diagnosis

visceral bias

visceral arousal (negative/positive feelings towards patients) leads to poor diagnostic decisions

availability bias

considering easily remembered diagnoses more likely irrespective of prevalence

base rate neglect

pursuing zebras

representativeness

ignoring atypical features that are inconsistent with the favored diagnosis

confirmation bias

seeking data to confirm, rather than refute the initial hypothesis

premature closure

stopping the diagnostic process too soon

steps of clinical reasoning

1. Identify the problem

2. Frame the differential

3. Organize the differential diagnosis list

4. Limit the list

5. Explore possible diagnoses using the H and P findings

6. Rank the differential list

7. Test the hypotheses

8. Re-rank with new data

9. Test the new hypotheses

ranking differential diagnosis

4 approaches to ranking

Possibilistic

-consider all known causes equally likely and simultaneously test for all of them

Probabilistic

-consider first the disorders that are more likely

-highest pretest probability -> probability that a disease is present before further testing is done

Prognostic

-consider the most serious diagnoses first

Pragmatic

-consider the diagnoses most responsive to treatment first

creating a differential diagnosis

Anatomic

-based on affected location (e.g., chest pain → cardiac, pulmonary, GI)

Organ/system

-by body system (cardiac, neuro, renal, etc.)

Physiologic

-by underlying mechanism (obstructive, infectious, inflammatory, metabolic)

Pivotal points

-key features or red flags that narrow possibilities (e.g., sudden onset, fever, weight loss)

treatment plan

-disposition

-further work up/evaluation

-consulation/referrals

-treatment (non pharm, pharm, therapeutic education/procedures)

-follow up

-patient education/health maintenance

social determinants of health

factors like income, education, housing, food security, employment, cultural background, and access to healthcare affect how patients present, what treatments they can adhere to, and what follow-up is realistic

a good management plan must be feasible within the patient's context