Randomization, Blinding, and Intention-to-Treat

Question 1

Why is randomization a crucial process in a clinical trial?

Answer 1

• It minimizes selection bias
• It aims to ensure that treatment and control groups differ only in treatment received
• It allows for stronger inferences

Question 2

Stratification

Answer 2

• The process of classifying clinical trial participants into strata: subgroups of participants formed by classification on variable(s) assed at baseline
• Stratified allocation is a method of treatment assignment in which participants in each strata are assigned treatment within the defined subgroups
• Stratified randomization is random treatment assignment within defined subgroups

Question 3

Concealed Allocation

Answer 3

• Person who generatess the random assignment remains blind to the subject’s health conditions and thus cannot influence what treatment arm the person enters
• If allocation is not concealed, investigators are prone to assign healthier patients to the intervention arm which can result in selection bias

Question 4

Allocation Concealment vs Blinding

Answer 4

Question 5

Unblinded (AKA Open Label)

Answer 5

All parties are aware of the treatment the participant receives

Question 6

Single Blind

Answer 6

One part, either the participant or the investigator, is unaware of the treatment allocation to the participant

Question 7

Double Blind

Answer 7

The participant and the clinicians/data collectors are unaware of the treatment the participant receives

Question 8

Triple Blind

Answer 8

Particpants, clinicians/data collectors, and outcome adjudicators/data analysts are all unaware of the treatment the participant receives

Question 9

Per-protocol analysis

Answer 9

• Only the patients who fully complied with the protocol were included in the analysis
• Does not include any cross overs and provides a fair idea of the efficacy of treatment
• However, this removes the benefits of randomization

Question 10

Intention to treat analysis

Answer 10

• All patients who were enrolled in the study and randomly allocated are included in the analysis

Question 11

Relative Risk

Answer 11

• The risk of the outcome in the treated group (expirimental event rate or EER) compared to the risk in the control group (control event rate or CER)
• Relative Risk (RR) = (EER)/(CER)

Question 12

Absolute Risk Reduction

Answer 12

• The difference in risk between the control group (CER) and the experimental group (EER)
• Absolute Risk Reduction (ARR) = (CER) - (EER)

Question 13

Number Needed to Treat (NNT)

Answer 13

• The number of patients that must be treated over a given period of time to prevent one additional outcome
• NNT = 1/ARR

Question 14

Incidence

Answer 14

• The occurrence rate or frequency of a disease

Question 15

Prevalence

Answer 15

• Proportion of a particular population found to be affected by a medical condition at a specific time
• Decreases through two processes:
  
  • These patients are cured
  • These patients die
• This means that the prevalence can increase if it becomes more common or we prevent patients from dying from the disease. Thus an increase in prevalence can be a good thing if it means fewer deaths with better treatments.