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