Flashcards in Day 3.1 Behavioral Science Deck (135):

1

## Case-control study

###
Gp of people w disease vs Gp of ppl w/o disease

Retrospective (looks back in time)

Observational- looking at possible risk factors for dz (not nec a causal relationship)

Asks "What happened?"

2

## What is the measurement for a case-control study?

###
Odds ration (OR = ad / bc)

E.g. pts w COPD had higher odds of a hx of smoking than pts w/o COPD

3

## Cohort study

###
Compares Gp w risk factor to Gp w/o risk factor to determine if risk factor increases likelihood of dz

Prospective (forward in time)

Observational

Asks "What will happen?"

Clinical trials are cohorts.

4

## Measurement for cohort study?

###
Relative Risk (RR = [a/(a+b)] / [c/(c+d)]

E.g. smokers have a higher risk of developing COPD than non-smokers

5

## Cross-sectional study

###
Assesses freq of dx (and related risk factors) at a particular pt in time.

Observational

Asks "What is happening now?"

6

## Measurement for cross-sectional study?

###
Dz prevalence

Can show risk factor association, but doesn't show causality

7

## Twin concordance study

###
Measures heritability.

Compares freq with which both monozygotic twin or both dizygotic twins develop a dz

8

## Adoption study

###
Compares siblings raised by biologic vs by adoptive parents.

Measures heritability vs influence of env factors

9

## What is meta-analysis?

###
Pools and integrates data from many studies to get an overall conclusion. Has greater statistical power.

"Highest echelon of clinical evidence"

Limitations: quality of individual studies; bias in study selection

10

## 2x2 table

###
Disease is on top, test is on side

TP FP

FN TN

pos/neg are horizontal

11

## Sensitivity eqn

###
TP / [TP + FN]

Or, 1 - FN

12

## What is sensitivity?

###
Proportion of all people with dz who test positive. (TP over all people w/ disease)

Also, the ability of a test to detect a dz when it is present.

SNOUT - SeNsitivity rules OUT dz

13

## Specificity eqn

###
TN / [TN + FP]

Or, 1 - FP

14

## What is specificity?

###
Proportion of all people w/o dz who test negative (TN over all pts w/o dz)

Also, the ability of a test to indicate non-dz when no dz is present.

SPIN = SPecificity rules IN

15

## Are HIV tests sensitive or specific?

###
First test is ELISA - it's very Sensitive but has a high FP rate (SN rules OUT, so it's better to get everyone who might have it rather than miss someone who doesn't).

If positive ELISA could be TP or FP, so confirm with Western Blot, which is specific, and high FN rate.

SP rules IN. So use Western as confirmatory test.

16

## Which should be more sensitive, screening tests, or confirmatory tests? Which should be more specific?

###
Screening = Sensitive (SN rules OUT- so need to get all the possible positives- even if they are FP)

Confirmatory/diagnosing tests should be specific

SP rules IN.

17

## Eqn PPV

### TP / [TP + FP]

18

## What is PPV?

###
The proportion of all positive results that are accurate.

Probability that pt has dz if pt has a pos test result

19

## Eqn NPV

### TN / [TN + FN]

20

## What is NPV?

###
Proportion of neg test results that are correct.

Probability that a pt does not have dz, given negative result

21

## How does high prevalence affect PPV and NPV?

###
If there are a lot of pts w dz, the number of TP will go up, and the number of FN will also go up (bc more pts have it, and some of those will wrongly test negative).

Increased TP means increased PPV.

Increased FN means NPV will decrease.

22

## How does low prevalence affect PPV and NPV?

###
If prevalence is low, then the FP will go up, and also to TN will go up.

Increased FP means decreased PPV

Increased TN means increased NPV

23

## Will a test be more accurate in a population with high prevalence or low prevalence?

### High prevalence means a high PPV, and low NPV, so the test will peform better w high prevalence. This is why you should only screen pts who need screening.

24

## What is (point) prevalence?

###
total cases / total population at risk

this is at one point in time.

25

## What is incidence?

###
NEW cases during a given period / pop at risk during that period.

Incidence is NEW incidents only.

Pts who already have it don't count.

26

## How can you approximate prevalence using incidence?

### Prevalance is approx incidence (new cases) x disease duration

27

## For chronic dz, which is larger, prevalence or incidence?

###
Prevalence is bigger than incidence

Bc duration is longer. There are more overall cases than there are new cases, bc it lasts so long

e.g. diabetes

28

## For acute dz, which is larger, prevalence or incidence?

###
They are equal. Prevalence (everyone that has it) and incidence (new cases) are the same, since the dz doesn't last long enough for prevalence to be bigger. (duration is short)

e.g. common cold

29

## Odds ratio eqn

### OR = AD / BC

30

## What is odds ratio?

###
Odds of having dz in exposed divided by odds of having dz in unexposed.

Use for case-control studies (retrospective)

31

## Relative risk eqn

### RR = [a / (a+b)] / [c / (c+d)]

32

## What is the relative risk?

###
Probability or getting the dz in the exposed gp vs getting the dz in the unexposed gp.

For cohort studies (prospective)

33

## Attributable risk eqn

### AR = [a / (a+b)] - [c / (c+d)]

34

## What is attributable risk

###
The difference (so subtract!) in risk bt exposed [a / (a+b)] and unexposed [c / (c+d)] groups

Or, the proportion of dz that is attributable to the exposure.

Ex smoking causes 1/3 of the cases of pneumonia

35

## Absolute risk reduction eqn

###
ARR = [a / (a+b)] - [c / (c+d)]

Note: same as AR, but now chart has risk factor Reducer rather than risk factor.

36

## What is absolute risk reduction?

###
Difference in risk reduction between treatment (exposed) vs placebo (unexposed).

Same as attributable risk, but now looking at a risk factor reducer (treatment) rather than a risk factor.

37

## What is the NNT?

###
1/ARR

Remember, ARR is looking at risk factor Reducers (aka TREATments) So the NNT is related to this.

Number of pts who have to get treatment before the drug successfully treats one pt. Want it to be low.

38

## What is the NNH?

###
1/AR

AR looks at risk factors (HARMful things), so the NNH is related to the AR.

The number of pts who could have the risk factor before one pt was harmed. Want it to be high.

39

##
Fornicators: 30% have HPV

Non-fornicators: 5% have HPV

What is the attributable risk of fucking to getting HPV?

###
AR = Exposed - unexposed

30-5 = 25%

40

## If 10,000 pts took a drug and 100 were saved by it, what is the NNT?

###
NNT = 100.

Need to treat 100 patients in order to save 1 patient

(10,000 drug / 100 saved = 100 drug / 1 saved)

41

## What is precision?

###
Consistency and reproducibility of a test (reliability)

Absence of random variation in a test.

42

## What is accuracy?

### Trueness of test measurements (validity)

43

## Do random error and systemic error reduce precision or accuracy?

###
Random error = reduced precision

Systemic error = reduced accuracy.

44

## RR < 1

###
The dz is LESS likely to occur in the group

Or, the factor is protective

45

## RR > 1

###
The dz is MORE likely to occur in the exposed group

Or, the factor is harmful.

46

## RR = 1

### The factor makes no difference

47

## What is validity?

### Accuracy

48

## What is reliability?

### Precision

49

## How to reduce bias?

###
1. blind studies (dbl blind is better)

2. placebo responses

3. crossover studies (switch treatment/placebo halfway through; ea subj acts as own control)

4. randomization

50

## What is bias?

###
One outcome is systematically favored over another. Systematic errors.

(Systematic error = reduced accuracy/validity)

51

## Selection bias

###
Non-random assignment to study group

Berkson's bias: using hospitalized pts

52

## Recall bias

### Knowing presence of disorder alters the recall by pts

53

## Sampling bias

###
Subj not representative of general pop

So results can't be generalized to general pop

54

## Late-look bias

###
Info gathered at inappropriate time. This is a type of recall bias.

E.g. Giving a survey to study a fatal dz- only live pts can answer

55

## Procedure bias

###
Subj in diff gps not treated the same

eg Treatmt gp gets more attn, stimulating greater compliance

56

## Confounding bias

### 2 closely assocd factors- one factor has an effect on the other and distorts/confuses the effect of the 2nd factor

57

## Lead-time bias

###
Early detection is confused with increased survival- happens with improved screening for dz

The natural hx of dz is not changed, but bc of early detection, survival time seems to be increased

58

## Pygmalion effect

### Researcher's belief in efficacy of rx chgs the outcome of the rx

59

## Hawthorne effect

### The group being studied changes its behavior bc they know they are being studied.

60

## What is positive skew?

###
mean > median > mode.

Asymmetry w TAIL on right.

61

## What is negative skew?

###
mean < median < mode

Asymm with TAIL on left

62

## What measurement is least affected by outliers in the same?

### Mode

63

## In a normal gaussian distribution, where are the mean, median, and mode?

###
in the middle. they all equal each other.

note: in bimodal (2 humps), there are 2 modes, so two peaks.

64

## What is the null hypothesis (H0)

### Hypothesis of no difference (no assoc bt dz and risk factor)

65

## What is the alternative hypothesis (H1)

### There IS a difference (there's an assoc bt dz and risk factor)

66

## Type I error (alpha)

###
Saying there IS a difference when there isn't one.

Mistakenly accepting experimental hypothesis and rejecting null.

False-positive error.

67

## What is the probability of making a Type I error?

###
probability = p

p is judged against alpha, a pre-determined level of significance (usu <.05)

68

## What is a Type II error (beta)

###
Stating that there is NOT a difference where actually there is one.

Not rejecting the null when the null is false and should have been rejected

False-negative error.

69

## What is the probability of making a Type II error?

### Beta

70

## Setting a guilty man free- what type of error?

### Type II (Beta)

71

## Convicting an innocent man- what type of error?

### Type I (alpha)

72

## What is power?

###
Being right.

The likelihood of rejecting a null hypothesis when it is false and should be rejected, or the likelihood of finding a difference when a difference does exist.

73

## What happens to power when you increase the sample size?

###
It increases.

Power in numbers!

74

## Eqn for Power

### 1- beta

75

## What does power depend on?

###
1. total # of end points experienced by population (don't want study drop-outs)

2. Difference in compliance bt treatmt groups

3. Size of expected effect (easier to be wrong abt a 1 year life expectancy increase than abt a 15 year increase)

76

## What is the standard error of the mean?

###
st dev / (sq rt of sample size)

sigma / sq rt of n

SEM decreases as n increases

77

## Normal gaussian distributions at st dev of 1, 2, 3

###
1 st dev = 68% (34+34)

2 st dev = 95% (42.5+42.5)

3 st dev = 99.7% (~50+50)

also 1.645 st dev = 90%

78

## What is confidence interval?

### Likelihood that if you repeated a study, the repeat would fall in the same range as the original

79

## Eqn for CI

###
CI = mean +/- Z(SEM)

Z = predetermined level of confidence that you want to attain. The Z for 95% is 2 (actually 1.96)

SEM = st dev / sq rt sample size

Don't forget to do + and - so get it on either side of the mean!

80

## 68% what is the Z?

### 1

81

## 99.7% what is the z?

### 3

82

## 90% what is the z?

### 1.645

83

## 95% what is the z?

### 2 (but actually 1.96)

84

## If the 95% CI for a mean difference between 2 variable includes 0, what does this mean?

### If it includes 0, it means that 0 is a possible answer for if the means are different. If the means can have zero difference, it means that there is no difference between the two treatments.

85

## If the 95% CI for odds ration or relative risk includes 1, what does this mean?

###
If RR =1, no difference between the two groups.

So H0 is not rejected.

86

## If the CI between 2 groups overlaps, what does this mean?

### The groups are not significantly different.

87

## 99% what is the z?

### 2.57

88

## t-test

### checks differences bt the means of 2 groups

89

## ANOVA test

### checks differences bt the means of 3 or more groups

90

## x2 (Chi squared) test

###
checks differences bt 2 or more PERCENTAGES or proportions of categorical outcomes.

Unlike t-test and ANOVA, is NOT looking at means.

91

## Disease prevention classifications

###
PDR: prevent, detect, reduce disability

primary prevention: prevent dz occurrence (vaccine)

secondary prevention: early detection (pap smear)

tertiary prevention: reduce disability from dz (chemo)- not really prevention of dz at this point, just prevention of effects.

92

## Correlation coefficient

###
r, measures correlation bt 2 variables

closer to 1 means closer correlation

r is from -1 to 1

-1 means inversely correlated

0 means not correlated either way

1 means positively correlated

Coefficient of determination = r^2 (r squared)

Correlation does not imply causation.

93

## Prevention measures for diabetics

###
Serum glucose levels

HbA1C (2x/year)

urine microalbumin- proteinurea, indicative of diabetic renal dz

serum lipids (coronary artery dz)

BP

foot exams (neuropathy, poor circ = injury)

dilated eye exam (retinopathy, cataracts, glaucoma)

influenza and pneumococcal vaccines

94

## Prevention measures of high-risk sexual behavior

###
HIV and syphilis screening

HBV vaccine

GC/Ch screen

Pap smear

HPV screen and vaccine

counsel on STDs and condom use

95

## Prevention measures for smoking

###
Address quitting at each encounter

Avoid Vit A supplements (excess Vit A incrs lung cancer risk)

avoid OCP in women over 35 (incr DVT, thrombembolism)

abd US in males 65-75 to r/o AAA (abd aortic aneurysm)

influenza and pneumococcal vaccines

96

## Prevention measures for drug use

###
Hepatitis vaccines

HIV and TB testing

97

## Prevention measures for alcoholism

###
Influenza, pnuemococcal vaccines

TB test

98

## Prevention measures for overweight

### Blood sugar tests for diabetes

99

## Prevention measures for homeless, recent immigrant, inmates

### TB test

100

## Reportable dz

###
STDs:

HIV, Gonorrhea, Syphillis

Hepatitis:

A, B, C

Immunizations:

MMR, Chickenpox

Diarrheal:

Salmonella, Shigella

TB

101

## Leading causes of death in infants (<1yo)

###
Congential Abn

Short gestation (low birthweight)

SIDS

Maternal complications of prego

Respi distress syndrome

102

## Leading causes of death in 1-14yo

###
Injuries

Cancer

Congenital anomalies

Homicide

Heart dz

103

## Leading causes of death 15-24yo

###
Injuries

Homicide

Suicide

Cancer

Heart Dz

104

## Leading causes of death 25-64

###
Cancer- 1st

Heart dz

Injuries

Suicide

Stroke

105

## Leading causes of death 65+

###
Heart Dz

Cancer-2nd

Stroke

COPD

Pneumonia

Influenza

106

## Premium

### Amt the insured pt has to pay to the insurance company, monthly.

107

## Co-pay

###
Amt insured pt pays at time of service

eg $30 for clinic visit

$15 for meds

108

## Deductable

###
Yearly amt- amt that insured pt has to pay out of pocket before the insurance company will pay. Once deductable is met, insurance company pays everything else

Pts get procedures at end of year bc of this

109

## What is the financial duty of the pt w insurance?

###
Monthly premium

Co-pays

Deductable

110

## What is the financial duty of the insurance company?

### Health care expenses beyond what the pt pays- beyond co-pay and beyond deductable

111

## What is the risk the pt takes in buying insurance?

### Paying more to insurance than what is received in medical care

112

## What is the risk the insurance company has in providing insurance to the pt?

### Paying more for medical care than they get from the patient.

113

## What is the reward to the pt and to the insurance company?

###
Reward to pt: financial benefit if cost of medical care exceeds cost of insurance

Reward to insurance company: financial benefit if pt pays more than cost of medical care

114

## Pre-existing condition

### Condition that pt already has that insurance will not cover (bc it's too financially risky for insurance to cover it)

115

## Lifetime maximum

### Max amt that an insurance company will pay in life. e.g. 3 mil.

116

## Network

### Group of healthcare providers that has agreed to a reduced payment in order to have access to a larger number of pts

117

## HMO

###
Health Maintenance Organization

PCP is gateway to specialist care

Provider must be in-network for insurance to cover the cost.

118

## PPO

###
Preferred Provider Org

No gatekeeper to specialist (can see w/o going to PCP)

Provider does not have to be in-network, but out-of-network is more expensive to pt

119

## Formulary

### The list of meds that an insurance company will pay for

120

## Utilization Management (UM)

###
Dept that evaluates appropriateness, necessity, and efficiency of healthcare services (w/in a hospital or clinic)

See if pt can leave earlier, if billing is maximized, etc

121

## Resource-based Relative Value Scale

###
Scale that determines what a doc should be paid for a specific procedure (CPT code) or specific service in a certain region of the country- based on amt of work req'd to do procedure, regional practice expense, and regional malpractice expense.

RVU = relative value unit. Different procedures in diff locations have diff RVUs

122

## MCO / Health Plan

###
Managed Care Org / Health Plan / Health Care Org

Org that tries to maximize quality/minimize cost.

Encourages pts/docs to choose less costly care, controls in-pt admissions and length of stay, emphasizes prevention

123

## Options for pts w/o access to care

###
Medicare

Medicaid

CHIP

VA (federally funded)

City/County/State funded health networks (e.g. tax that goes toward indigent care in that area)

Federally funded teaching hospitals

Universal health care

124

## 4 ways physicians are compensated

###
Fee-for-service

Capitation

Salary

Pay for performance

125

## Fee-for-service

###
Payment in exchange for a specific service

eg surgical procedure (compensation based on RVU)

clinic visit (higher complexity = reimbursed more)

in-pt visit

126

## Capitation

###
Fixed payment for a period of time or for a number of pts (a cap on time, pts), regardless of number of procedures

eg ER shift, minor emergency shift

Concierge practice (fixed fee one year, do anything pt needs in that year)

HMO- bank of pts, get paid flat rate to treat all of them, no matter how often/not they see you

127

## Salary

###
Specified amt regardless of work performed

Universities

Hospital admin

HMO

128

## Pay for performance

###
Payment is increased if a physician meets pre-established targets

eg MCO/Health care org pays more for meeting vaccine targets, HbA1C <7.5

129

## Medicare, Medicaid

###
Federal programs, started by amendments to social security act

MedicarE - Elderly (65+, disability, or end stg renal dz needing dialysis)

MedicaiD - Destitute. federal/state assistance for very low income pts

130

## Medicare Part A

###
Covers:

hospital (anything in-pt)

skilled nursing

hospice

homecare

131

## Medicare Part B

###
Covers:

Doctor bills

Anything out-pt

Labs, Xrays

OT, PT

132

## Medicare Part C

###
Medicare advantage.

Combo of A + B

Paid for by govt but run by private insurance companies

133

## Medicare Part D

### Stand-alone prescription drug coverage

134

## CHIP

###
Children's Health Insurance Program

Matching state and federal funding for child health coverage

135