82 terms

USMLE

STUDY
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Terms in this set (...)

Cross-Sectional Study
Collects data from a group of people to assess frequency of disease at a particular point and time.
DOES NOT establish causality.

What is happening now??
Case-Control Study
Compares a group of people with disease to a group without the disease.
OR-Odds Ratio

What happened in the past??
Cohort Study
Compares a group with a given exposure or risk factor to a group without such exposure.
Likelihood of disease
RR-Relative Risk

Does exposure increase disease?
Twin Concordance Study
Compares the frequency with which both monozygotic twins or both dizygotic twins develop the same disease.
Measures heritability and the influence of environmental factors.
Adoption Study
Compares siblings raised by biological vs. adoptive parents.
Measures heritability and the influence of environmental factors.
Clinical Trial
Experimental study involving humans. Compares therapeutic benefits of two or more treatments, or of treatment and placebo.
Study quality improves: randomized, controlled or double blinded.
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.
=TP/(TP +FN)
SN-N-OUT=highly Sensitive test, when Negative, rules OUT disease.
Specificity (True Negative Rate)
Proportion of all people without disease who test negative, or the probability that when the disease is absent, the test is negative.
=TN/(TN +FP)
SP-P-IN=highly SPecific test, when Positive rules IN disease.
Positive Predictive Value
Proportion of positive test results that are true positive. Probability that a person who has a positive test result actually has the disease.
PPV=TP/(TP +FP)
Negative Predictive Value
Proportion of negative test results that are true negative. Probability that a person with a negative test result actually does not have the disease.
NPV=TN/(TN+FN)
Incidence Rate
Number of New Cases/Number of People at Risk.
Looks at new cases (incidents).
Prevalence
Number of Exiting Cases/Total Number of People in a Population
Prevalence looks at all current causes.
Odds Ration
Typically used in Case-Control studies. Odds that the group with the disease (cases) are exposed to a risk factor divided by the odds that the group without the disease (controls) was exposed.

OR=ad/bc
Relative Risk
Typically used in cohort studies. Risk of developing disease in the exposed group divided by the risk in the unexposed group.
Attributable Risk
The difference in risk between exposed and unexposed groups, or the proportion of disease occurrences that are attributable to the exposure.
Relative Risk Reduction
The proportion of risk reduction attributable to the intervention as compared to a control.
Absolute Risk Reduction
The difference in risk (not the proportion) attributable to the intervention as compared to a control.
Number Needed to Treat
Number of patients who need to be treated for one patient to benefit.
Number Needed to Harm
Number of patients who need to be exposed to a risk factor for one patient to be harmed.
Precision
The consistency and reproducibility of a test (reliability).
The absence of random variation.

High precision = low random error
Accuracy
The trueness of test measurements (validity). The absence of systemic error or bias in the test.
high accuracy=low systemic error
Selection Bias
Error in assigning subjects to a study group resulting in an unrepresentative sample. Most commonly a sampling bias.
Recall Bias
Awareness of disorder alters recall by subjects; common in retrospective studies.
Measurement Bias
Information that is gathered in a systemically distorted manner.
Procedure Bias
Subjects in different groups are not treated the same.
Observer-Expectancy Bias
Researcher's belief in the efficacy of a treatment changes the outcome of that treatment.
Confounding Bias
When a factor is related to both the exposure and outcome, but not on the casual pathway-factor distorts or confuses effect of exposure on an outcome.
Lead-Time Bias
Early detection is confused with increased survival.
Measures of Central Tendency
Mean=(Sum of values)/(Total number of values)
Median=Middle value of a list of data sorted from least to greatest.
Mode=Most common value.
Measures of Dispersion
Standard Deviation=how much variability exits form the mean in a set of values.
Standard Error the Mean= an estimate of how much variability exists between the sample mean and the true population.
SEM=SD/sqrt (n)
Percentages for gaussian distribution-standard deviations
1: 68%
2: 95%
3: 99.7%
Bimodal
Suggests two different populations.
Positive Skew
Typically, mean is greater than the median which is greater than the mode. Asymmetry with longer tail on the right.
Negative Skew
Typically the mean is less than the median which is less than the mode. Asymmetry with longer tail on the left.
Null Hypothesis
Hypothesis of no difference or relationship.
Alternative Hypothesis
Hypothesis of some difference or relationship.
Type I Error (Alpha)
Stating that there is an effect or difference when none exists. Also known as false-positive error. Measure of p value
Type II Error (Beta)
Stating that here is not an effect or difference when one exists. also known as false-negative error.
Beta-you were Blinded by the truth.
How can you reduce a Type II error?
increase sample size
increase expected effect size
increase precision of measurement
What are factors that can increase the power of a study?
increase sample size
decrease standard deviation
increase p value (type I error)
increase difference between groups
Confidence Interval
Range of values within which the true mean of a population is expected to fall, with a specified probability.
T-Test
Checks differences between the means of two groups.
Tea is meant for two.
ANOVA
Checks differences between means of three or more groups.
Chi-Square
Checks differences between two or more percentages or proportions of categorical outcomes (not mean values).
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.
Beneficence
Physicians that have special ethical duty to act in the patients best interest. May conflict with autonomy or what is best for society.
Nonmaleficence
"Do no harm." Must be balanced against beneficence; if the benefits outweigh the risks, a patient may make an informed decision to proceed.
Justice
To treat persons fairly and equitably. This does not always imply to equally.
Advance Directives
Instructions given by a patient in anticipation o the need for a medical decision. Details vary per state law.
Oral Advance Directive
Incapacitated patient's prior oral statements commonly used as a guide. Variance in interpretations.
What is the priority of surrogate decision makers?
SPOUSE ChiPS in

1. Spouse
2. Children
3. Parent
4. Sibling
4 parts of informed consent
1. Disclosure
2. understanding
3. capacity
4. Voluntary

Exceptions:
1. lack decision-making capacity
2. implied consent in emergencies
3. therapeutic privilege
4. waiver
When is parental consent not required?
Sex: STI, contraception, pregnancy
Drugs: substance abuse
Rock-Roll: emergency/trauma
Exceptions to confidentiality
SAVED

Suicide/homicide
Abuse (child)
Victim--duty to protect
Epileptic
Diseases-reportable
Developmental Milestones Infant 0-12 Months of Age(Parents Start Observing)
P: Primitive reflexes disappear (moro, rooting, palmar, Babinski), posture (lifts head up prone), picks (passes toys hand to hand), Points (to observed objects).

S: Social smile, stranger anxiety, separation anxiety.

O: orients-voice, then name and gestures, object permanence, oratory (says "mama" and "dada."
Infant 0-12mos: Motor reflexes
P

P Primitive reflexes disappear
1. Moro--3mos
2. rooting--4 mos
3. Palmar--6mos
4. Babinski (up)--12mos

Posture
1. lifts head--1mos
2. rolls/sits--6mos
3. stands--10mos
4. walks--12-18mos

Points to objects
1. by 12mos
Infant 0-12mos: Social
S

Social smile--2mos
Stranger anxiety--6mos
Separation anxiety--9mos
Infant 0-12mos: Verbal/Cognitive
O

Orients
1. to Voice--4mos
2. to name/gestures--9mos.

Object Permanence
1. by 9mos

Oratory
1. says mama/dada--10mos.
Developmental Milestones Toddler 12-36 Months of Age (Child Rearing Working)
C: Cruises, climbs stairs, cubes stacked, cultured, kicks ball.

R: Recreation (parallel play), reapproachemnt (moves away form and then returns to mother), realization (core gender identity formed).

W: Words (200 words by age 2).
Toddler 12-36 mos: Motor
C

Cruises-steps by 12 mos.
Climbs stairs--18mos.
Cubes stacked--#=agex3
Cutlery--20mo
Kicks ball--24 mos.
Toddler 12-36mos: Social
R

Recreation--parallel play 24mos
Rapproachement-leave/return to mom-24mos
Realization--core gender formed-36mos
Toddler 12-36mos: Verbal/Cognitive
W

Words
1. 200 by age 2
2. 2 word sentences
Developmental Milestones Preschool 3-5 Years of Age (Don't forget, they're still Learning)
D: drive (tricycle), drawing, dexterity (hops on one foot, using zippers).

F: Freedom (spending the day away from mother), friends.

L: Language (1,000 words by age 3), legends (tell detailed stories).
Preschool 3-5yr: Motor
D

Drive
1. tricycle-3 years

Drawings
1. copies line/circle-4 yr.

Dexterity*
1. hops on 1 foot--4 yrs
2. buttons/zippers--5 yrs
Preschool 3-5yr: Social
F

Freedom
1. spends part of day away--3yr

Friends
1. cooperative play--4yr
Preschool 3-5yr: Verbal/Cognitive
L

Language
1. 1000 words by 3
2. complete sentences/prepositions--4yrs

Legends
1. tells detailed stories--4yrs
Children should be rear-facing till age_______ and in car seats with harness until age________
2; 4
Older children should use a booster until age______
8
Children under age ______ should not ride in a seat with a front facing airbag
12
What are the 4 parts of Medicare?
*A*: hospital AA: hospital *A*dmission
*B*: *B*asic medical BB: *B*asic medical Bills
*C*: CombC: *C*ombo of A+B
*D*: DD: *D*rugs
#1 cause of death in young adults?
Unintentional injury
#1 cause of death in infants?
congenital malformations
#1 cause of death in elderly?
Heart disease
Primary Disease Prevention
Prevent disease before it occurs (HPV Vaccination).
Secondary Disease Prevention
Screen early for and manage existing but asymptomatic disease (Pap smear for cervical cancer).
Tertiary Disease Prevention
Treatment to reduce complications form disease that is ongoing or has long-term effects (Chemotherapy).
PDSA Cycle
Process improvement model to test changes in real clinical setting.
Plan-define problem and solution
Do-test new processes
Study-measure and analyze data
Act-to integrate new process into regular workflow.
Active Error
Occurs at level of frontline operatory (wrong IV pump dose programmed).
Latent Error
Occurs in processes indirect from operator but impacts patient care (different types of IV pumps used within same hospital).
Root Cause Analysis
Use records and participant interviews to identify all the underlying problems that led to an error. Categories of causes include process, people (providers or patients), environment, equipment, materials, and management.

Retrospective
Failure Mode and Effects Analysis
Use inductive reasoning to identify all the ways a process might fail and prioritize these by their probability of occurrence and impact on patients.

Prospective
Metyrapone stimuation test
Blocks cortisol synthesis by inhibiting 11-beat-hydroxylase (converts 11-deoxycortisol to cortisol) in the zone fasciculata

Decreases cortisol

Increases in pituitary ACTH secretion

Leads to increased 11-deoxycortisol and further metabolized to hydroxycorticosteroids that accumulate in the urine (if both these metabolites increase than that means an intact HPA axis)