Evidence based practice Randomised controlled trial (2)


1. Which of the following may potentially make the result of a randomised controlled trial INVALID?

Choose 4 of the following options.
   The randomised list was concealed from the clinicians. VALUE="The follow-up period was incomplete.">
   The follow-up period was incomplete.
   The follow-up period was too short for the measured outcomes to be manifested.
   Clinicians were blind to the treatment the patients were receiving.
   The assessors knew which treatments the patients were receiving.
   Patients initially randomised to the treatment group but failed to comply with treatment were analysed in the control group.
   The characteristics of the treatment group were similar to the controls.


2. Which of the following measures do NOT vary with the initial risk of the patients?

Choose 2 of the following options.
   Relative risk
   Absolute risk reduction
   Relative risk reduction
   Numbers needed to treat


3. Which of the following items measure the magnitude of the treatment effects?

Choose 2 of the following options.
   p values
   absolute risk reduction
   relative risk reduction
   control event rate


4. Which of the following estimates suggest that the treatment is effective? (Assume that the outcome being measured is bad)

Choose 2 of the following options.
   Absolute risk reduction is - 0.5 (-50%).
   Relative risk reduction is 0.2 (20%)
   The number needed to treat is 2.
   The relative risk is 1.8.


5. Which of the following estimates suggest the treatment is harmful? (Assume the outcome measured is bad.)

Choose 2 of the following options.
   The relative risk is 2.5.
   The absolute risk reduction is 0.2 (20%).
   The relative risk reduction is 0.4 (40%).
   The number needed to treat is –5.


6. You consider it worthwhile to switch to a new treatment only if you are reasonably certain that the absolute risk reduction (ARR) for your patient exceeds 0.3 (30%). Which of the following estimates for your patient will prompt you to use this treatment?

Choose 3 of the following options.
   ARR = 0.4 (95% CI –0.2 to 0.8)
   ARR = 0.6 (95%CI 0.5 to 0.7)
   ARR = 0.2, p<0.0001
   ARR = 0.4 (95% CI 0.35 to 0.47)
   NNT = 2 (95% CI 1 to 3)
   NNT = 5 (95% CI 4 to 6)


7. The following scenario refers to questions 7 to 12. In a randomised controlled trial, 1000 and 500 patients were randomised to the control and treatment groups respectively. At the end of the trial, 300 and 100 patients died in the control and treatment groups respectively. You estimated that without treatment, the risk of your patient dying is about 10%. The relative risk of dying in this study is

One answer only.
   0.33
   0.5
   0.67
   1
   1.5
   2
   3


8. The relative risk reduction is

One answer only.
   0.33
   0.5
   0.67
   1
   1.5
   2
   3


9. The absolute risk reduction IN THE STUDY is

One answer only.
   0.033 (3.3%)
   0.05 (5%)
   0.1 (10%)
   0.2 (20%)
   0.33 (33%)
   0.5 (50%)


10. The numbers needed to treat IN THE STUDY is

One answer only.
   3 *10
   20
   30
   50
   100


11. The absolute risk reduction FOR YOUR PATIENT is

One answer only.
   0.033 (3.3%)
   0.05 (5%)
   0.1 (10%)
   0.2 (20%)
   0.33 (33%)
   0.5 (50%)


12. The numbers needed to treat FOR YOUR PATIENT is

One answer only.
   3
   10
   20
   30
   50
   100