03/03/15 - Evidence Based Medicine (SECOND HALF EMPHASIZED)

Question 1

The aim of this study type is to quantify the relationship between factors.

A. Descriptive
B. Analytical

Answer 1

B. Analytical

The aim of a descriptive study is to explain or characterize a population.

Question 2

An analytical study in which the population is surveyed at a single point in time for risk factors and disease outcomes.

A. Randomized-control trial
B. Cross-sectional
C. Case-control
D. Cohort

Answer 2

B. Cross-sectional

Question 3

An analytical study in which the intervention is randomly allocated

A. Randomized-control trial
B. Cross-sectional
C. Case-control
D. Cohort

Answer 3

A. Randomized-control trial

Question 4

An analytical study in which the outcomes were determined prior to the exposure being determined.

A. Randomized-control trial
B. Cross-sectional
C. Case-control
D. Cohort

Answer 4

C. Case-control

Question 5

An analytical study in which the outcomes were determined some time after the exposure/intervention was determined

A. Randomized-control trial
B. Cross-sectional
C. Case-control
D. Cohort

Answer 5

D. Cohort

Question 6

“Standard therapy for newly diagnosed glioblastoma is radiotherapy plus temozolomide. In this study, we evaluated the effect of the addition of bevacizumab to radiotherapy-temozolomide for the treatment of newly diagnosed glioblastoma”. What type of study is this?

A. Clinical trial
B. Case-control
C. Meta-analysis
D. Cohort

Answer 6

A. Clinical Trial

Question 7

“In this study we evaluted the effect of the addition of bevacizumab for the treatment of glioblastoma. A total of 458 patients were assigned to the bevacizumab group, and 463 to the placebo group”. What stage of testing is this?

A. Phase I
B. Phase II
C. Phase III
D. Phase IV

Answer 7

C. Phase III

Question 8

A study synthesized the results of published research on Parkinson’s disease, finding 8 eligible studies involving hundreds of normal and parkinson’s patients. What type of study is this?

A. Clinical Trial
B. Case-control
C. Meta Analysis
D. Cohort

Answer 8

C. Meta analysis

Question 9

Your bathroom scale consistently gives measurements that are 5 pounds lighter than the true weight. What is the type of error and is it imprecise or inaccurate?

A. Systematic error; reduced accuracy
B. Systematic error; reduced precision
C. Random error; reduced accuracy
D. Random error; reduced precision

Answer 9

A. Systematic Error; reduced accuracy

Question 10

As part of a study, the investigator questions patient subjects about previous IV drug use. It is found that the patients consistently underreport IV drug use in the interview. What type of bias is present?

A. Procedure bias
B. Confounding
C. Social desirability bias
D. Hawthorne effect

Answer 10

C. Social desirability bias

Procedure bias is when subjects are not treated the same (eg the treatment group is known). The Hawthorne effect is when people act differently when they know they are being watched.

Question 11

Which of these factors is not an effective method to reduce bias in medical studies?

A. Double-blind studies
B. Placebo responses
C. Randomization
D. Ambiguous standards
E. Multiple observers

Answer 11

D. Ambiguous standards

Derp.

Question 12

A study on blood glucose levels of a popiulation reveals the mean and median values were higher than the mode. This statistical distribution can best described as:

A. Gaussian distribution
B. Bimodal
C. Positive skew
D. Negative skew

Answer 12

C. Positive skew

Gaussian distribution would have the same mean, median, and mode. It cannot be determined if the distribution is bimodal.

Question 13

A researcher is analyzing weight in kilograms of 2 groups of patients in a cohort study. What statistical method should be used?

A. Chi-square test
B. T-test
C. Cox-proportional hazard regression
D. ANOVA

Answer 13

B. T-test

Use a T-test to compare 2 groups, and ANOVA to compare 3 or more.

Question 14

A researcher is analyzing post-operative pain caused by a new surgical method on a 1-10 scale. What statistical method should be used?

A. Chi-square test
B. T-test
C. Cox-proportional hazard regression
D. ANOVA

Answer 14

A. Chi-square test

Use chi-square test to estimate the likelihood that the samples are representative of overall population. Chi-square tests are for categorical data, which apparently, this is.

Question 15

An odds ratio is used to assess risk or benefit in what type of epidemiological study design?

A. Randomized-control trial
B. Cross-sectional
C. Case-control
D. Cohort

Answer 15

C. Case-control

Question 16

Answer 16

Relative risk = EER/CER = 0.25/0.75 = 1/3

Absolute risk reduction = CER - EER = 0.5

Number needed to treat = 1/ARR = 2

Question 17

You postulate that a population is getting dysentery from drinking sewage water. Your null-hypothesis for an upcoming study is:

A. People drinking sewage are more likely to get dysentery compared those drinking from clean lakes
B. There is no difference in dysentery rates between those who drink clean vs sewage water.
C. Both of the above.

Answer 17

B. There is no difference in dysentery rates between those who drink clean vs sewage water.

A is the alternative hypothesis.

Question 18

You conduct a study that supports a null hypothesis despite certainty that a difference should exist. This is an example of a:

A. Type I Error; alpha
B. Type II Error; alpha
C. Type I Error; beta
D. Type II Error; beta

Answer 18

D. Type II Error; beta

Alpha/beta correspond to Type I/II, respectively. A type II error is failing to reject a null hypothesis when there is a difference, while a type I error is rejecting it when there isn’t a difference.

Question 19

Which errors are more important to reduce for initial screening tests? Diagnostic tests?

A. Alpha; Alpha
B. Alpha; Beta
C. Beta; Alpha
D. Beta; Beta

Answer 19

C. Beta; Alpha

Type II errors are dangerous for initial screens, since they fail to recognize a difference (false negative). Type I errors are dangerous for diagnostic screens since they can misdiagnose (false positive).

Question 20

A patient tests positive for HIV. They insist you tell them how likely they actually have the disease in light of the positive test. What do you tell him or her?

A. There is a 97% chance they are HIV infected
B. There is a 98.5% chance they are HIV infected
C. There is a 17% chance they are HIV infected
D. There is a 0.3% chance they are HIV infected

Answer 20

C. There is a 17% chance they are HIV infected

This is looking for the PPV; which can be calculated as the proportion of positive screens that actually had the disease. This is 30/(150+30), or 1/6 = 0.1666667.

Question 21

While counseling a patient on a positive screening test, you find out that the patient belongs to a population with a higher prevalence of the disease than the general population (from which your epidemiological data is derived). What can you conclude?

A. The PPV of the test is higher than you estimated
B. The PPV of the test is lower than you estimated
C. The sensitivity of the screen decreases
D. The sensitivity of the screen increases
E. The PPV and sensitivity are the same regardless of prevalence.

Answer 21

A. The PPV of the test is higher than you estimated

Question 22

Diagnosis of Huntington’s disease used to be based on symptoms; the average life-span post-diagnosis was 15 years. A person invents a genetic test for diagnosing Huntington’s and markets it as “drastically improving post-diagnosis survival”. What type of bias may be present?

A. Sampling bias
B. Late-look bias
C. Pygmalion effect
D. Lead-time bias

Answer 22

D. Lead-time bias

Lead-time bias is when survival duration increases simply because the disease is detected in an earlier stage. Late-look bias results from the deaths of those with advanced disease not being able to complete studies. The pygmalion effect is when people perform better when higher expectations are placed on them.

Question 23

A marathon runner was diagnosed with IT-band syndrome and is immediately scheduled appointments with a physical therapist. What preventative technique is being used?

A. Primary prevention
B. Secondary prevention
T. Tertiary prevention

Answer 23

C. Tertiary prevention

Minimizing sequelae or recurrence once a disease has occurred.

Question 24

An injured runner refers her friend to a physical therapist so that he can learn strength, conditioning, and training tips. What preventative technique is being used?

A. Primary prevention
B. Secondary prevention
C. Tertiary prevention

Answer 24

A. Primary prevention

Reducing the occurrence of a disease or injury.