Clinical Trials

5. Design Issues

Exercise 7

For each of the following example scenarios, select which blinding method you think is the best match. A blinding method may apply to more than one scenario.

Blinding Methods:

  • Unblinded
  • Single blind
  • Double blind
  • Triple blind

Example 1: A cardiac specialist wants to compare a new aspirin like tablet with an existing one for chronic heart disease and wants patients, doctors and the research team not to be able to tell which patient is in which treatment groups.

Example 2: An orthopaedic hospital team wants to compare two different types of artificial hip joints available for patients needing hip replacements.

Example 3: A gastroenterology surgeons want to evaluate keyhole (laparoscopic) versus an open operation to remove patients’ gallbladders in a trial.

Example 4: A novel oral antithrombotic agent is to be compared with an existing oral agent for long term prophylaxis against strokes. Both patients and doctors are not aware of which treatment a patient is on.

Example 5: A chemotherapeutic intervention for early leukemia is to be compared to a “watch and wait” approach. It is unclear how many patients will experience disease progression.

Example 6: Two different formulations for pre-colonoscopy bowel preparation are to be compared to see which empties the colon the best. The patients are instructed not to inform the doctor performing the procedure which agent they received.

Answers:
Example 1: A cardiac specialist wants to compare a new aspirin like tablet with an existing one for chronic heart disease and wants patients, doctors and the research team not to be able to tell which patient is in which treatment groups.
Answer: TRIPLE BLIND
Explanation: Patients, investigators, and sponsor are all blinded.

Example 2: An orthopaedic hospital team wants to compare two different types of artificial hip joints available for patients needing hip replacements.
Answer: SINGLE BLIND
Explanation: Surgeons can see which type of joint is being used, but patients are unaware.

Example 3: A gastroenterology surgeons want to evaluate keyhole (laparoscopic) versus an open operation to remove patients’ gallbladders in a trial.
Answer: UNBLINDED
Explanation: It is difficult to blind if comparing invasive to non-invasive.

Example 4: A novel oral antithrombotic agent is to be compared with an existing oral agent for long term prophylaxis against strokes.
Answer: DOUBLE BLIND
Explanation: Both patients and investigators are blinded in this study.

Example 5: A chemotherapeutic intervention for early leukemia is to be compared to a “watch and wait” approach. It is unclear how many patients will experience disease progression.
Answer: UNBLINDED
Explanation: It would not be possible to use blinding.

Example 8: Two different formulations for pre-colonoscopy bowel preparation are to be compared to see which empties the colon the best. The patients are instructed not to inform the doctor performing the procedure which agent they received.
Answer: SINGLE BLIND
Explanation: patient knows allocation, doctor does not.