Epidemiology and ethics 1 Flashcards
Case fatality rate
percentage of people with a given disease who die within a certain amount of time
birth rate
live births per 1000
fertility rate
live births per 1000
of women aged 15-45 years
death rate
deaths/1000
neonatal mortality rate
neonatal deaths (first 28 days of life)/10000 live births
perinatal mortality rate
neonatal deaths+ stillbirths/1000 total births
infant mortality rate
deaths (from 0-1 yo)/1000 live births
maternal mortality rate
maternal pregnancy-related deaths (deaths while pregnant or in the first 42 days after delivery)/100,000 live births
relative risk
probability of getting disease in group that is exposed to risk factor, compared to (divided by) probability of getting that disease in people who are unexposed
A/(A+B)/C(C+D)
RR>1 positive disease
RR
Odds ratio
A/C divided by B/D
Attributable risk
difference in risk between exposed and unexposed
A/(A+B)- C/(C+D)
Absolute risk reduction
Conceptually similar to calculation of attributable risk, but opposute
C/(C+D)-A/(A+B)
NNT
1/ARR
The number of patients you would need to treat in order to save/affect one life
important to determine if a drug should be used or is cost effective
Sensitivity
Probability that a screening test will be positive in patients with a disease
A/(A+C)
Specificity
D/(B+D)
false positive rate= 1-specificity
PPV
PPV= A/(A+B)
what’s the value of the positive test result? likelihood that the person will be positive if they have tested positive
NPV
NPV= D/(C+D)
high prevalence gives high positive predictive value
low prevalence gives high negative predictive value
Likelihood ratio
does not depend on prevalence
odds of having a positive test result in individuals with a disease, compared with the odds of a positive result in those without the disease
(the positive person should test positive)
PLR= sensitivity/1-specificity
or sensitivity/false pos rate
NLR= 1-sensitivity/specificity
or false neg rate/specificity
Negative likelihood ratio
odds of having a negative test result in individuals with a disease compared with the odds of a negative result in those without the disease
NLR= 1-sensitivity/specificity
or false neg rate/specificity
PLR= sensitivity/1-specificity
or sensitivity/false pos rate
Accuracy
correct/true results
true pos/true neg/everything
Type i error
rejects null even though it’s true
Type II error
null hypothesis rejected even though it is false
beta error
Statistical significance
statistically detectable difference between 2 groups (not the same as clinical significance)
measured by the arbitraty p value
power
ability of study to detect a difference between 2 groups
Confidence interval
range of values in which the examiner can be (90,95, 99%) confident that the value obtained from the study truly reflects reality
ranges from
[mean-z(SEM)] to
[mean+z(SEM)]
z= 1.645 for 90%
- 96 for 95%
- 57 for 99%
if CI crosses 1, no relationship
if CI for 2 treatment groups crosses 0, there may be no difference between the 2 groups
What’s important in a screening test? in a confirmatory test?
sensitivity for screening (Catch everybody)
specificity for confirmation (eliminate false pos)
what percentage falls within 1,2,3 sd’s of the mean in a normal distribution?
68,95,99.7%
DMAIC for quality improvement
Define the problem
Measure: establish an objective baseline
Analyze- identify causes of the problem
Improve- identify and implement interventions (re-measure, re-analyze, and re-intervene as needed)
Control- maintain the improvement that you achieved
Identifies 2 groups: diseased group and healthy group. Retrospectively compares them. Weakened by recall and selection biases
case- control study
Seeks to estimate disease prevalence and exposure across a population
cross- sectional study
examines a collection of studies on a given subject
meta-analysis
prospective blinded study involving placebos, existing therapies, and experimental interventions
RCT
Focuses on ONE group with a shared exposure or disease and either prospectively or retrospectively compares them
cohort study
examines a collection of cases to seek insight into the disease of interest. Useful in rare diseases
case control
Memory errors produce incorrect data
recall bias
subject awareness of being studied alerts their answers and behaviors from normal
observational bias
certain medical studies attract subjects with particular medical histories rather than general population
selection bias
studies that show a difference are preferentially published and then later included in meta- analysis rather than studies that support the null hypothesis
publication bias
screening tests designed to detect asymptomatic disease may miss rapidly- progressive disease because the interval between successive screenings only detects slowly- progressive ones
length bias
screening test may allow earlier diagnosis of disease but does not translate into actual length of survival
Lead- time bias
exemptions from condifentiality
- patient allows physician to share information
- disease is legally reportable (HIV, STD, hepatitis, Lyne, door-borne, meningitis, rabies, TB, impaired ability to drive, child abuse, elder abuse)
- patient is suicidal or homicidal
- penetrating wound from an assault
- adolescent with a condition that is harmful to self or others
maintain adolescent confidentiality if pertaining to with STDs, pregnancy, or contraception
Informed consent
potential risks and benefits of proposed treatment
alternative treatments
risks of refusing treatment
pt can always change their mind
not required in an emergency
Capacity
patient has the mental ability to make decisions regarding his or her medical care
Competence is a legal thing
Competence- legalities
not psychotic or intoxicated
have understanding of medical situation
capable of making decisions
medical decisions by parents on behalf of minors may be legally overruled it…
considered harmful to the child
in an emergency, treat the patient despite the parents’ wishes and get the court order later
Durable power of attorney
designates a surrogate decision maker
makes decisions consistent with the patient’s values
“substituted judgment”
Living will
written document that details a patient’s wishes about specific medical situations
out of hospital DNR order
advance directive
Physician- assisted suicide
physician supplies patient with means of ending his or her life
- Oregon
- Washington
- Vermont
- Montana (exceptions)
- Canada
Euthanasia
physician actively ADMINISTERS lethal agent to patient, to end suffering
This is illegal in the US
Brain death
- irreversible absence of all brain activity
- > 6 hrs
- absence of cranial nerve reflexes
- apnea
- absence of brainstem- evoked responses, absence of cerebral circulation, or persistent isoelectric EEG
- Cannot be explained by a medical condition that mimics death (encephalopathy, hypothermia, intoxication, locked-in syndrome, Guillain-Barre syndrome)
Medical malpractice
Duty of care (legal obligation to conform to a reasonable standard of care)
breach of duty (failure to conform to the standard of care)
harm
causation (breach of duty is the cause of injury or harm)
What are the 2 ways that “standard of care” can be established in a malpractice case?
- expert testimony
2. Res ipsa loquitur “it speaks for itself” doctrine
Vicarious liability principle
supervisors are responsible for the actions of their subordinates
When can a physician refuse to treat a patient on the grounds of futility?
- no rationale for treatment
- maximal intervention has already failed
- treatment does not achieve the goals of care
