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Biostatistics & Pharmacoeconomics Flashcards

1
Q

What’s the median/ 50th percentile?

A

Value in the middle of a ranked list

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2
Q

When do u use the median value?

A

When data is skewed

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3
Q

What’s the mode?

A

Value that occurs most in a data set

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4
Q

What’s a “normal distribution” also known as?

A

Bell shaped or Gaussian curve

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5
Q

Characteristics of Gaussian or normal distribution?

A

Mean, mode and median would all have the same (similar) value.

Curve is symmetric around the mean

Skew = 0 (zero)

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6
Q

What’s a negatively skewed distribution (asymmetric)?

A

The mean, mode and median are not the same (similar)

The mean is towards the left of the distribution (and not in the center)

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7
Q

What’s a positively skewed distribution (asymmetric)?

A

The mean, mode and median are not the same (similar)

The mean is towards the right of the distribution (and not in the center)

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8
Q

Whats the p-value?

A

Likelihood (or probability) that result obtained was due to chance

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9
Q

What does p-value < 0.05 mean?

A

There’s less than a 5% probability that the result was obtained by chance

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10
Q

When do we fail to accept (reject) the null hypothesis?

A

When the p-value is smaller than the predetermined significant level (say < 0.05), indicating that the observed result is highly unlikely under the null hypothesis

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11
Q

When’s Confidence Interval (CI) considered significant in odds ratio, risk ratio or hazard ratio that compares 2 grps?

A

When the CI doesn’t include 1

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12
Q

When’s Confidence Interval (CI) considered significant between grps (or within the same grp over time)?

A

When the CI doesn’t include 0

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13
Q

Is the measure of “statistical significance” the same as “clinical significance”

A

No

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14
Q

What’s a type I error?

A

Also known as “false positive”

When the null hypothesis is true, yet it is rejected in error

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15
Q

What’s statistical power?

A

1 - B (type II error)

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16
Q

What does a higher statistical power imply?

A

Means that we can be more certain that the null hypothesis was correctly rejected

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17
Q

What’s relative risk/ risk ratio / RR?

A

Probability of an unfavorable event occurring in the tx grp versus the control grp

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18
Q

Howz RR expressed?

A

Decimal or percentage

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19
Q

Formular of RR?

A

Risk = number of subjects with unfavorable event
Divided by
Number of subjects in that arm

RR = Risk in tx group
divided by
Risk in control grp

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20
Q

How do u interpret RR = 1?

A

RR = 1: no difference in risk btw the 2 grps

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21
Q

How do u interpret RR < 1?

A

The event is LESS likely to occur in the tx grp than in control grp

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22
Q

How do u interpret RR > 1?

A

The event is MORE likely to occur in the tx grp than in control grp

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23
Q

A study compared metoprolol v. placebo in heart failure pts over 12 months. If HF progression occurred in 28% of placebo-treated pts and in 16% of metoprolol-treated pts.

Calculate the RR

Interprete the RR

A

RR = tx Grp/ control grp

  = 0.16/0.28 = 0.57 or 57%

T4, subjects treated with metoprolol were only 57% as likely as placebo-treated pts to have HF progression

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24
Q

What’s another formula for calculating RR?

A

RR = a/(a+b)
Divided by
c/(c+d)

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25
In a group of 100 smokers, 40 developed lung cancer while 60 didn't. In a similar grp of 100 non-smokers, lung cancer developed in 10 people. Calculate the RR Interpret the RR
RR = a/(a+b) divided by c/(c+d) RR = 40/(40+60) divided by. = 4 10/(10+90) Means that smokers are 4 times more likely to develop lung cancer than non-smokers
26
Formula for relative risk ratio (RRR)
RRR = (% risk in control grp - % risk in tx grp) divided by % risk in the control grp OR RRR = 1 - RR
27
A study compared metoprolol v. placebo in heart failure pts over 12 months. If HF progression occurred in 28% of placebo-treated pts and in 16% of metoprolol-treated pts. Calculate the RRR Interprete the RRR
RRR = (28% - 16%)/ 28% = 0.43 OR (1 - .57) There's a 43% relative risk reduction in HF progression in pts being treated with metoprolol
28
What's absolute risk reduction (ARR)?
Difference btw control grp event and tx grp events ARR = (% risk in control grp) - (% risk in tx grp)
29
A study compared metoprolol v. placebo in heart failure pts over 12 months. If HF progression occurred in 28% of placebo-treated pts and in 16% of metoprolol-treated pts. Calculate the ARR Interprete the ARR
ARR = (% risk in control grp) - (% risk in tx grp) ARR = 28% - 16% = 12% This is the difference in risk that can be attributed to the intervention (drug)
30
What's number needed to treat (NNT)?
NNT = 1/ (% risk in control grp) - (% risk in tx grp) OR NNT =. 1/ ARR (expressed as a decimal)
31
A study compared metoprolol v. placebo in heart failure pts over 12 months. If HF progression occurred in 28% of placebo-treated pts and in 16% of metoprolol-treated pts. Calculate the NNT Interprete the NNT
NNT = 1/ (% risk in control grp) - (% risk in tx grp). OR NNT = 1/ ARR (expressed as a decimal) NNT = 1/(0.28 - 0.16) = 8.3 round up always! = 9 T4 for every 9 pts who received metoprolol for 1 year, you would expect HF progression to be prevented in 1 pt
32
What's odd ratio? (OR)
OR is the ratio of the odds of an event offering in the tx grp to the odds of an event occurring in the control grp Measure of association btw exposure and an outcome
33
In a group of 100 smokers, 40 developed lung cancer while 60 didn't. In a similar grp of 100 non-smokers, lung cancer developed in 10 people. Calculate the OR Interpret the OR
Odds of a smoker developing lung cancer = 40/60 = 0.67 Odds of a non-smoker developing lung cancer = 10/90 = 0.11 T4 OR = 0.67/0.11 = 6 Means that smokers are 6 times more likely to develop lung cancer compared to non-smokers
34
What's the mean?
Average value of a sample distribution
35
What's a positive correlation graph?
Downward sloping line from right to left
36
What's a negative correlation graph?
Downward sloping line from left to right
37
What's a dependent variable?
Outcome of interest, which may change in response to some intervention
38
What's an independent variable?
The intervention
39
List types of discrete data
Nominal - consists of categories, where order is arbitrary e.g. Gender Ordinal - consist of ranked categories, but differences btw categories are not equal e.g. Likert scales, NYHA functional class
40
List types of continuous data (infinite number of possible values, such as height, weight)
Interval data - used to measure continuous data with legitimate mathematical values. The difference btw 2 consecutive values is consistent along any pt of the scale, but the zero pt is ARBITARY e.g, Celsius temp scale Ratio - has equal intervals btw values and a MEANINGFUL zero pt (height, weight, time, length)
41
List types is study types
Observational study Case-control Cohort Cross-sectional Randomized controlled trial (RCT) Crossover Non-inferior trial
42
What's a cohort study?
This study type follows the cohort over time (longitudinal) and the outcomes are compared to a subset of the grp who were not exposed to the intervention, such as a drug e.g. Framingham studies
43
List types of Cohort Study
Prospective Retrospective (e.g. Through pt medical charts)
44
What's unique about randomized controlled trial (RCT)? Effect of this?
Blinding occurs This may reduce bias
45
Formula of hazard ratio (HR)?
HR = Hazard in the tx arm/ Hazard in the control arm
46
What's single blinding in RCT?
Subjects don't know what they're receiving
47
What's double blinding in RCT?
Neither subject nor researcher know which subjects received the active drug v. placebo
48
Uses of RCT?
To test a med for efficacy and safety within a given pt population
49
What's pharmacoeconomics?
Pharmacoeconomics research identifies, measures, and compares the costs (direct, indirect and intangible) and consequences (clinical, economic and humanistic) of pharmaceutical pdts and services
50
List research methods used to determine impact if pharmaceutical pdt or service
Cost-effectiveness Cost-minimization analysis Cost-utility analysis Cost-benefit analysis
51
Purpose of pharmacoeconomic analysis?
They serve to guide optimal healthcare resource allocation, in a standardized and scientifically based manner
52
What's the ECHO model?
Economics, Clinical and Humanistic Outcomes
53
Uses of ECHO model?
Can be used to determine pharmacoeconomic benefit
54
What's the Economic outcomes in the ECHO model?
Include direct, indirect and intangible costs of the drug compared to a medical intervention
55
What's the Clinical outcomes in the ECHO model?
Include medical events that occur as a result of the tx or intervention
56
What's the Humanistic outcomes in the ECHO model?
Include consequences of the dx or tx as reported by the pt or caregiver (pt satisfaction, quality of life)
57
List the direct types of costs in pharmacoeconomic.
Direct medical costs Direct non-medical costs Indirect costs Intangible costs
58
What's direct medical cost?
Include medications, medication administration, hospitalizations, clinic visit, emergency room visits, nursing services
59
What's direct non-medical cost?
Include travel cost (gas, bus, hotel stays fir family), child care services (for children of patients)
60
What's indirect cost?
Include loss of productivity of the pt (and possibly of caregiver)
61
What's intangible cost?
Include pain and suffering, anxiety, weakness
62
What's the main advantage of cost-effectiveness analysis (CEA)?
Outcomes are easier to quantify when compared to other analyses. Clinicians and decision makers are familiar with these types of outcomes since they are similar to outcomes seen in clinical trials
63
Which is the most common methodology seen in the literature today?
Cost-effectiveness analysis (CEA)
64
What's a disadvantage of CEA?
The inability to directly compare different types of outcomes E.g. One can't compare the cost effectiveness of implementing a diabetes program v. Implementing an asthma program where the outcomes units are different (blood glucose values v. Asthma Exacerbations)
65
When is Cost-Minimization Analysis (CMA) used?
CMA is used when 2 or more interventions have already demonstrated equivalency in outcomes and costs of each intervention are being compared
66
What's the limitation of Cost-Minimization Analysis (CMA)?
The use of CMA is limited given its ability to compare ONLY alternatives with the same outcome
67
What's Cost-Benefit Analysis (CBA)?
CBA is a systematic process for calculating and comparing benefits and costs of an intervention in terms of monetary units That is, identifying all the benefits from an intervention and converting them into dollars in the year that they will occur
68
What's Cost-Utility Analysis (CUA)?
CUA is a specialized form of cost-effectiveness analysis (CEA) that includes a quality-of-life component associated with morbidity using common health indices such as quality-adjusted life years (QALYs) and disability-adjusted life years (DALYs)
69
What can you measure using CUA?
Quality of life (years gained) but NOT the "quality" or "utility"
70
Whats the cost measurement unit of the 4 basic pharmacoeconomic methodologies (CEA, CMA, CBA, CUA)?
Dollars
71
What's the outcome unit of CEA?
Natural units (life-years gained, mmHg blood pressure, mg/dL LDL etc)
72
What's the outcome unit of CMA?
Assumed to be equivalent in comparative grps
73
What's the outcome unit of CBA?
Dollars
74
What's the outcome unit of CUA?
Quality-adjusted-life-year (QALY) or other utilities

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