First Aid Step 1 - Public Health Sciences
Relative risk (RR)
Measures the risk of developing disease in the exposed group divided by risk in the unexposed group >> used in cohort studies
Hospice care
Medical care focused on providing comfort and palliation instead of definitive cure - priority is given to improving comfort and relieving pain - Available to patients on Medicare or Medicaid and in most private insurance plans whose life expectancy is <6 months
Nonmaleficence
"Do no harm." Must be balanced against beneficence - if the benefits outweigh the risks, a patient may make an informed decision to proceed (most surgeries and medications fall into this category)
4 exceptions to informed consent:
"WIPE" 1. Waiver from the patient 2. legally Incompetent patient who can't make their own decisions 3. therapeutic Privelege when disclosure would harm the patient 4. Emergency situations with implied consent
PrevaIence =
# of existing cases/total # in a population
Incidence =
# of new cases/# of people at risk
LR- =
(1-sensitivity)/specificity FN rate/TN rate
Hawthorne effect
(an example of measurement bias) participants change behavior upon awareness of being observed
Berkson bias
(an example of selection bias) cases and/or controls selected from hospitals are less healthy and have different exposures than general population
Attrition bias
(an example of selection bias) participants lost to follow up have a different prognosis than those who complete the study
Chi-square (X2)
(categorical data) Checks differences between 2 or more percentages or proportions of categorical outcomes EX: comparing percentage of members of 3 different ethnic groups who have essential hypertension
fisher's exact test
(categorical data) checks differences between 2 percentages or proportions of categorical, nominal outcomes - used instead of a chi-square test in small populations EX: comparing the percentage of 20 men and 20 women with hypertension
CFR% =
(deaths/cases) x 100
Type II error (B)
(false-negative error) Stating that there is not an effect or difference when one exists - null hypothesis is not rejected when it is in fact false
Type I error (a)
(false-positive error) Stating that there is an effect or difference when none exists - null hypothesis incorrectly rejected in favor of alternative hypothesis
t-test
(numerical data) Checks differences between means of 2 groups EX: comparing mean BP between men and women
ANOVA
(numerical data) Checks differences between means of 3 or more groups EX: comparing mean BP between 3 different ethnic groups
Mean =
(sum of values)/(total number of values)
how to reduce over-expectancy bias:
- Blinding (masking) - Use of placebo
how to reduce procedure bias:
- Blinding (masking) - Use of placebo
how to reduce recall bias:
- Decrease time from exposure to follow-up
how to decrease lead-time bias:
- Measure "back-end" survival (adjust survival according to the severity of disease at the time of diagnosis)
how to reduce selection bias:
- Randomization - Ensure the choice of the right comparison/reference group
Situations in which parental consent is usually not required:
- Sex (contraception, STIs, pregnancy) - Drugs (substance abuse) - Rock and roll (emergency/trauma)
how to reduce measurement bias:
- Use objective, standardized, and previously tested methods of data collection that are planned ahead of time - Use placebo group
3 ways to increase power and decrease B:
- increase sample size - increase expected effect size - increase precision of measurement
how to decrease confounding bias:
- multiple/repeated studies - crossover studies (subjects act as their own controls) - Matching (patients with similar characteristics in both treatment and control groups)
how to decrease length-time bias:
- randomized controlled trial assigning subjects to the screening program or to no screening
if the 95% confidence interval for odds ratio or relative risk includes 1 then:
- the H0 is not rejected
if the 95% confidence interval for a mean difference between two variables includes 0 then:
- there is no significant difference - H0 is not rejected
p is judged against a preset value for a, which is usually ____
0.05
power =
1 - B
3 most common causes of death: 45-64 years
1. Cancer 2. Heat Disease 3. Unintentional Injury
Conditions with frequent hospital readmissions: Private
1. Chemotherapy 2. Mood Disorders 3. Complications of Surgery
3 most common causes of death: <1 year
1. Congenital malformations 2. Preterm Birth 3. SIDS
Conditions with frequent hospital readmissions: Medicare
1. Congestive HF 2. Septicemia 3. Pneumonia
3 most common causes of death: 65+ years
1. Heart Disease 2. Cancer 3. Chronic Respiratory Disease
Conditions with frequent hospital readmissions: Uninsured
1. Mood Disorders 2. Alcohol 3. Diabetes w/ complications
Conditions with frequent hospital readmissions: Medicaid
1. Mood Disorders 2. Schizophrenia/Psychosis 3. Diabetes
3 most common causes of death: 15-34 years
1. Unintentional Injury 2. Cancer 3. Heart Disease
3 most common causes of death: 1-14 years
1. Unintentional Injury 2. Suicide 3. Homicide
what percent of a sample lies within +/- 1 SD of the mean?
68%
what percent of a sample lies within +/- 2 SD of the mean?
95%
what percent of a sample lies within +/- 3 SD of the mean?
99.7%
LR- < ____ indicates a highly sensitive test
<0.1
if p<0.05 for a study outcome, then the probability of obtaining that result purely from chance is ____
<5%
relative risk reduction =
= 1-RR (RR = [a/(a+b)] / [c/(c+d)])
NNH =
= 1/AR AR = [a/(a+b)] - [c(c/d)]
NNT =
= 1/ARR ARR = [c/(c+d)] - [a/(a+b)]
ARR =
= [c/(c+d)] - [a/(a+b)]
LR+ > ____ indicates a highly specific test
>10
4 parts of Medicare:
A = hospital insurance, home hospice B = basic medical bills C = (A+B) provided by approved private companies D = prescription drugs
Meta-analysis
A method of statistical analysis that pools summary data (means, RRs) from multiple studies for a more precise estimate of the size of an effect - Also estimates heterogeneity of effect sizes between studies - Improves strength of evidence and generalizability of study findings
Informed consent
A process that requires: - Disclosure via discussion of pertinent information - Capacity and an ability to understand - Voluntariness and freedom from manipulation
decision-making capacity
Ability to understand and process information and make a choice regarding appropriate medical care - determined by a physician for a specific healthcare-related decision (versus competency, which is determined by a judge and refers to global categories of decision making)
Recall bias
Awareness of disorder alters recall by subjects - common in retrospective studies
Adoption study
Compares siblings raised by biological vs adoptive parents - Measures heritability and influence of environmental factors
Odds ratio
Depicts the odds of a certain outcome given an exposure (disease; a/c) vs the odds of the outcome in the absence of that exposure (no disease; b/d) >> used in case control studies
lead-time bias
Early detection is confused with increased survival
Confounding bias
Factor related to both exposure and outcome (but not on causal path) distorts effect of exposure on outcome - EX: ice cream sales and robberies
Swiss cheese model
Focuses on systems and conditions rather than an individual's error - The risk of a threat becoming a reality is mitigated by differing layers and types of defenses >> Patient harm can occur despite multiple safeguards when "the holes in the line up"
Human factors designs
Forcing functions (those that prevent undesirable actions) are the most effective
Normal distribution
Gaussian/bell-shaped curve - the mean, median, and mode are all the same
Bundle Payment
Healthcare organization receives a set amount per service, regardless of ultimate cost to be divided among all provides and facility
Null (H0) Hypothesis
Hypothesis of no difference or relationship >> theory that there is no association between the disease and the risk factor in the population
Alternative (H1) Hypothesis
Hypothesis of some difference or relationship >> theory that there is some association between the disease and the risk factor in the population
Quaternary disease prevention
Identifying patients at risk of unnecessary treatment, protecting from the harm of new interventions (EX: imaging studies)
Consent for minors
In general, parental consent should be obtained, but exceptions exist for emergency treatment or if minor is legally emancipated Physicians should always encourage healthy minor-guardian communication. Physician should seek a minor's assent even if their consent is not required.
Oral advance directive
Incapacitated patient's prior oral statements commonly used as guide for decision making - Problems arise from variance in interpretation
Measurement bias
Information is gathered in a systemically distorted manner - EX: using a broken tool to measure BP
Advance directives
Instructions given by a patient in anticipation of the need for a medical decision
Phase III Drug Trial
Involves a large number of patients randomly assigned either to the treatment under investigation or to the standard of care (or placebo) Purpose: asks is it as good or better?" - Compares the new treatment to the current standard of care
Phase II Drug Trial
Involves a moderate number of patients with disease of interest Purpose: asks "does it work?" - Assesses treatment efficacy, optimal dosing, and adverse effects
Phase I Drug Trial
Involves a small number of healthy volunteers or patients with disease of interest purpose: asks "is it safe?" - assesses safety, toxicity, pharmacokinetics, and pharmacodynamics
Phase IV Drug Trial
Involves post-marketing surveillance of patients after treatment is approved Purpose: asks "can it stay?" - Detects rare or long-term adverse effects (eg, black box warning) - Can result in treatment being withdrawn from Market
Likelihood ratio
Likelihood that a given test result would be expected in a patient with the target disorder compared to the likelihood that the same result would be expected in a patient without the target disorder +> 10 and /or -<0.1 indicate a very useful diagnostic test.
Selection bias
Non-random sampling or treatment allocation of subjects such that study population is not representative of target population - Most commonly a sampling bias
Number needed to harm (NNH)
Number of patients who need to be exposed to a risk factor for I patient to be harmed >> Higher number = safer exposure
Number needed to treat (NNT)
Number of patients who need to be treated for I patient to benefit >> Lower number = better treatment
Autonomy
Obligation to respect patients as individuals (truth-telling, confidentiality), to create conditions necessary for autonomous choice (informed consent), and to honor their preference in accepting or not accepting medical care
Active error
Occurs at level of frontline operator - cause an immediate impact EX: wrong IV dose given
Latent error
Occurs in processes indirect from operator but impacts patient care - considered to be an "accident waiting to happen"
Safety culture
Organizational environment in which everyone can freely bring up safety concerns without fear of censure - Facilitates error identification
Medical power of attorney
Patient designates an agent to make medical decisions in the event that he/she loses decision-making capacity - Patient may also specify decisions in clinical situations - Can be revoked by patient if decision-making capacity is intact >> More flexible than a living will
Global payment
Patient pays for all expenses associated with a single incident of care with a single payment - Most commonly used during elective surgeries, as it covers the cost of surgery as well as the necessary pre-and post operative visits
Fee-for-service
Patient pays for each individual service
Discounted fee-for-service
Patient pays for each individual service a ta discounted rate predetermined by providers and payers (eg, PPOs)
Case fatality rate (CFR)
Percentage of deaths that occur over the disease course
Beneficence
Physicians have a special ethical (fiduciary) duty to act in the patient's best interest - May conflict with autonomy (an informed patient has the right to decide) or what is best for society (EX: mandatory TB treatment) >> Traditionally, patient interest supersedes
Capitation
Physicians receive a set amount per patient assigned to them per period of time, regardless of how much the patient uses the healthcare system - Used by some HMOs
Primary disease prevention
Prevent disease before it occurs (EX: vaccination)
Positive predictive value (PPV)
Probability that a person who has a positive test result actually has the disease varies directly with pretest probability (baseline risk, such as prevalence of disease): high pretest probability
Negative predictive value (NPV)
Probability that a person with a negative test result actually does not have the disease - varies inversely with prevalence or pretest probability
PDSA cycle
Process improvement model to test changes in real clinical setting Plan- define problem and solution Do- test new process Study- measure and analyze data Act- integrate new process into workflow
Sensitivity (true-positive rate)
Proportion of all people with disease who test positive, or the probability that when the disease is present, the test is positive
Specificity (true-negative rate)
Proportion of all people without a disease who test negative, or the probability that when the disease is absent, the test is negative
Preferred provider organization
Provider: Patient can see providers outside network Specialist: No referral required Payment: Higher copays and deductibles for alIservices
Point of service
Provider: Patient can see providers outside network Specialist: Requires referral from primary care provider Payment: Higher copays and deductibles for out-of- network services
Accountable care organization
Provider: Providers voluntarily enroll Specialist: Providers voluntarily enroll Payment: Medicare
Exclusive provider organization
Provider: Restricted to limited panel (except emergencies) Specialist: No referral required
Health maintenance organization
Provider: Restricted to limited panel (except emergencies) Specialist: Requires referral from primary care provider Payment: Denied for any service that does not meet established, evidence-based guidelines
Confidence interval
Range of values within which the true mean of the population is expected to fall, with a specified probability
Observer-expectancy bias
Researcher's belief in the efficacy of a treatment changes the outcome of that treatment
Secondary disease prevention
Screen early for and manage existing but asymptomatic disease (EX: pap smear for cervical cancer)
length-time bias
Screening test detects diseases with long latency period, while those with shorter latency period become symptomatic earlier
____ and ____ are fixed properties of a test ____ and ____ vary depending on disease prevalence in population being tested
Sensitivity and specificity positive predictive value (PPV) and negative predictive value (NPV)
Written advance directive
Specifies specific healthcare interventions that a patient anticipates he or she would accept or reject during treatment for a critical or life-threatening illness - EX: A living will
Correct result
Stating that there is an effect or difference when one exists (null hypothesis rejected in favor of alternative hypothesis) or Stating that there is no effect or difference when none exists (null hypothesis not rejected)
Procedure bias
Subjects in different groups are not treated the same
Bimodal distribution
Suggests two different populations EX: metabolic polymorphism such as fast vs slow acetylators, age at onset of hodgkin lymphoma, suicide rate by age
____ error decreased accuracy in a test
Systematic error
Negative predictive value (NPV) =
TN/(TN+FN)
specificity =
TN/(TN+FP)
Sensitivity =
TP/(TP+FN)
Positive predictive value (PPV) =
TP/(TP+FP)
Precision (reliability)
The consistency and reproducibility of a test - The absence of random variation in a test
Absolute risk reduction (ARR)
The difference in risk (not the proportion) attributable to the intervention as compared to a control
Attributable risk (AR)
The difference in risk between exposed and unexposed groups
Accuracy (validity)
The trueness of test measurements - The absence of systematic error or bias in a test
Justice
To treat persons fairly and equitably
Tertiary disease prevention
Treatment to reduce complications from disease that is ongoing or has long-term effects (EX: chemotherapy)
Cross-sectional study
Type of study that assesses frequency of disease and frequency of risk-related factors are assessed in the present - functions to measure disease prevalence - Functions to ask "What is happening?"
Case-control study
Type of study that compares a group of people with a disease to a group without a disease - Looks to see if odds of prior exposure or risk factor differ by disease state - functions to measure the odds ratio - functions to ask "What happened?"
Cohort study
Type of study that compares a group with a given exposure or risk factor to a group without such exposure - Looks to see if exposure or risk factor is associated with later development of disease - functions to measure relative risk - Can be prospective (asks "Who will develop disease?") or retrospective (asks "Who developed the disease [exposed vs nonexposed]?")
Crossover study
Type of study that compares the effect of a series of 2 or more treatments on a participant - Order in which participants receive treatments is randomized - Washout period occurs between each treatment >> Allows participants to serve as their own controls
Twin concordance study
Type of study that compares the frequency with which both monozygotic twins vs both dizygotic twins develop the same disease - Measures heritability and influence of environmental factors
AR% =
[(RR - 1)/RR] x 100
AR =
[a/(a+b)] - [c(c/d)]
RR =
[a/(a+b)] / [c/(c+d)]
root cause analysis
a retrospective medical error analysis approach that is applied after a failure event to prevent recurrence - uses records and participant interviews to identify all underlying problems and mistakes that lead to an error
odds ratio (OR) =
ad/bc
never event
an adverse event that is identifiable, serious, and usually preventable - a major error that should never occur EX: scalpel remains in a patient's abdomen
Standard error
an estimate of how much variability exists in a (theoretical) set of sample means around the true population mean
RR<1 means:
an exposure is associated with decreased disease occurrence
RR>1 means:
an exposure is associated with increased disease occurrence
Medicare
available to patients >65, <65 with certain disabilities, and those with end-stage renal disease
what type of study functions to measure an odds ratio?
case-control
what type of study functions to measure relative risk?
cohort
what type of study functions to measure disease prevalence?
cross-sectional
what type of study allows participants to serve as their own controls?
crossover
an increase in precision of a test leads to a ____ in standard deviation
decrease in SD
an increase in NPV will cause a ____ in prevalence
decrease in prevalence
clinical trials
experimental study that involves humans and compares the therapeutic benefits of ≥2 treatments or a treatment and a placebo - have 4 phases
in sensitivity, a value approaching 100% is desirable for ruling out disease and indicates a low ____ rate
false-negative rate
in specificity, a value approaching 100% is desirable for ruling in disease and indicates a low ____ rate
false-positive rate
failure mode and effect analysis (FMEA)
forward-looking medical error analysis approach that is applied before a process is implemented to prevent failures - uses inductive reasoning to identify all the ways a process might fail and prioritize them by probability of occurence and impact on patients
Deficient designs
hinder work flow and lead to staff workarounds that bypass safety features
Standard deviation
how much variability exists in a set of values, around the mean of these values
decrease in risk factors: incidence = prevalence =
incidence = decreases prevalence = decreases
extensive vaccine administration: incidence = prevalence =
incidence = decreases prevalence = decreases
faster recovery time: incidence = prevalence =
incidence = n/a prevalence = decreases
increased mortality: incidence = prevalence =
incidence = n/a prevalence = decreases
increased survival time: incidence = prevalence =
incidence = n/a prevalence = increases
an increase in precision of a test leads to a ____ in statistical power
increase in statistical power
an increase in PPV will cause a ____ in prevalence
increase prevalence
Surrogate decision-maker
individuals (surrogates) who know the patient and must determine what the patient would have done if the patient loses decision-making capacity and has not prepared an advance directive Priority of surrogates: - spouse - adult children - parents - siblings - other relatives
Medicaid
joint federal and state health assistance for people with limited income and/or resources
____ is the measure of central tendency most affected by outliers
mean
Negative skew distribution
mean < median < mode Asymmetry with longer tail on left
Positive skew distribution
mean > median > mode Asymmetry with longer tail on right
Balancing Quality Measurement
measure the impact on other systems/outcomes
Outcome Quality Measurement
measure the impact on patients
Process Quality Measurement
measure the performance of system as planned
Structural Quality Measurement
measure the physical equipment, resources, facilities
Median =
middle value of a list of data sorted from least to greatest
____ is the measure of central tendency least affected by outliers
mode
Mode =
most common value
as sample size increases, confidence interval ____
narrows
- r value = ____ correlation between variables
negative correlation
double-blind
neither the participant nor the researcher known whether the participant is in the treatment or the control group
+ r value = ____ correlation between variables
positive correlation
prevalence ____ (<, >, =) incidence for a short duration disease (like the common cold)
prevalence = incidence
prevalence ____ (<, >, =) incidence for a chronic disease (like diabetes)
prevalence > incidence
Do not resuscitate (DNR) order
prohibits cardiopulmonary resuscitation (CPR) - Other resuscitative measures that may follow (EX: feeding tube) are also typically avoided
burnout
prolonged excessive stress that leads to: - cynicism - detachment - decreased motivation and interest - sense of failure and helplessness - decreased immunity >> medical errors due to lack of concern
Pearson correlation coefficient
r is always between -1 and +1 The closer the absolute value of r is to 1, the stronger the linear correlation between the 2 variables
____ error decreases the precision of a test
random error
Confidentiality
respect for a patient's privacy and autonomy
Tests with a high ____ are used for screening
sensitivity
LR+ =
sensitivity/(1-specificity) = TP rate/FP rate
____ of processes reduces wasteful activities
simplification
fatigue
sleep deprivation that leads to: - low energy and motivation - cognitive impairment >> medical errors due to intellectual function
Tests with a high ____ are used for confirmation
specificity
____ of processes improves process reliability
standardization
triple-blind
the participant, researcher, and data analyst don't know whether the participant is in the treatment or control group
a
the probability of making a type I error (stating that there is an effect or difference when none exists)
B
the probability of making a type II error (stating that there is not an effect or difference when one actually exists)
statistical power
the probability of rejecting the null hypothesis when it is actually false
Relative risk reduction
the proportion of risk reduction attributable to the intervention as compared to a control
RR=1 means:
there is no association between an exposure and disease
if the CIs between two groups do not overlap, then:
there is probably a statistically significant difference between the two
