Biostats

Question 1

A pharmacist is considering which beta blocker should be preferred at his institution. He has narrowed his search down to two agents. Each drug provides similar health benefits, has similar tolerability and is dosed once daily. The pharmacist will base his decision on the drug that can be purchased at the lower cost. He will use the following analysis to choose the beta blocker for his institution’s formulary:
Answer

A
A cost-minimization analysis
B
A cost-effectiveness analysis
C
A cost-control analysis
D
A cost-benefit analysis
E
A cost-utility analysis

Answer 1

A
A cost-minimization analysis

Incorrect
Once the benefit of various drugs is considered equivalent (such as choosing which ACEIs or ARBs to have on the formulary), the next step is to find which one is less expensive.

Question 2

A pharmacy intern has been asked by his preceptor to gather 200 discharged patient charts from the chart room. He has been told that half the charts should be patients who received proton pump inhibitor (PPI) therapy while hospitalized. The other half should be patients with similar conditions and length of stay but who did not receive PPI therapy. The pharmacist wishes to conduct a study to see if there is any difference in the incidence of nosocomial infection in the PPI group versus the non-PPI group. Which of the following describes this type of study? (Select ALL that apply.)
Answer

A
Cohort study
B
Meta analysis
C
Case-control study
D
Randomized controlled trial 
E
Observational study

Answer 2

A
Cohort study
E
Observational study

Incorrect
A cohort study is a type of observational study (there is no intervention). This study describes a retrospective cohort (the cohort is discharged patients). These patients are then evaluated to determine if they were receiving PPIs, and then the outcome of nosocomial pneumonia is assessed. To be a case-control study, one would need to start out by identifying the outcome (the patients who developed pneumonia) which was not done at the onset of the study.

Question 3

Which of the following statements regarding specificity are true?
Answer

A
It refers to the percentage of time a test is negative when disease is not present.
B
It refers to the percentage of time a test is positive when disease is not present.
C
It refers to the percentage of time a test is negative when disease is present.
D
It refers to the percentage of time a test is positive when disease is present.
E
It is equal to 1 – type II error.

Answer 3

Which of the following statements regarding specificity are true?
Answer

A
It refers to the percentage of time a test is negative when disease is not present.

Question 4

A clinical trial is conducted on a new drug, LoSod. LoSod is found to reduce serum sodium to 131 mEq/L, with a 95% confidence interval of 128.7 mEq/L to 133.3 mEq/L. What is the correct interpretation of this 95% confidence interval?
Answer

A
There is a 95% chance that the interval contains the true population value.
B
When using this drug in a larger population, one can expect that 95% of the patients will have a serum sodium between 128.7 to 133.3 mEq/L.
C
When using this drug in a larger population, one can say with 95% confidence that the serum sodium will be 131 mEq/L.
D
There is a 5% chance that the true population mean is within the stated range.
E
There is a 5% chance that the results of this study are rejected in error.

Answer 4

A
There is a 95% chance that the interval contains the true population value.

Incorrect
A confidence interval gives an estimated range of values which is likely to include an unknown population parameter; the estimated range being calculated from a given set of sample data.

Question 5

The pharmacist is presenting a clinical trial to the medical team. The trial includes a 95% confidence interval for the primary endpoint. If the confidence interval was greater (98% or 99%), what effect will be seen with the interval?
Answer

A
The interval will be wider.
B
The interval will be more narrow.
C
There will be no effect on the interval.
D
The interval will no longer have valid meaning at a greater confidence level.
E
It will cause the p-value to be invalid.

Answer 5

A
The interval will be wider.

Incorrect
The range of numbers will be bigger if the confidence interval is higher. For example, to be 99% confident that the true value for the population falls in the range, the interval will be wider (e.g., closer to 3 SD from the mean) than a 95% confidence interval (where the values fall within 2 SD of the mean). Applied to a clinical scenario, if the 95% confidence interval for decrease in A1C is 2-3% (meaning you are 95% confident that all patients will have a decrease in A1C between 2-3%), then your range will need to be bigger (e.g., 4-6%) to be 99% confident of the decrease in A1C experienced by all patients. This concept should not be confused with precision of the data as discussed on page 189-190 of the 2018 RxPrep Course Book.

Question 6

A clinical trial evaluated the effects of a chemotherapeutic drug given to patients with osteosarcoma. The trial duration was three months and the primary endpoint was mortality. During this time, there were two deaths among patients receiving placebo and one death among patients receiving active drug with an equal amount of patients randomized to each arm. It could be stated that the drug decreased the risk of death by 50% (as the “relative risk” of death is 0.5). The benefit sounds great, but in reality the benefit was very small. Choose the correct statements: (Select ALL that apply.)
Answer

A
The relative risk can be used to make a small benefit appear larger than is warranted.
B
Relative risk is also called the risk ratio.
C
Relative risk tells you little about the actual risk outside the controlled clinical trial.
D
A relative risk > 1 means that fewer events are occurring in the treatment group compared to the control group.
E
A relative risk < 1 means that fewer events are occurring in the treatment group compared to the control group.

Answer 6

A
The relative risk can be used to make a small benefit appear larger than is warranted.
B
Relative risk is also called the risk ratio.
C
Relative risk tells you little about the actual risk outside the controlled clinical trial.

E
A relative risk < 1 means that fewer events are occurring in the treatment group compared to the control group.

Incorrect
Relative risk (RR) gives you a measure of the risk of an event in one group compared to the risk of that event in a comparison group. It does not give you an idea of how important (or large) the treatment effect really is in the population-at-large.