The Anatomy and physiology of a RCT

Question 1

Why do a RCT

Answer 1

One strength!
To address to confounding (i.e people in intervention group because they want to, already a bias)
So groups consist of pretty equal characteristics

Question 2

Concealed allocation

Answer 2

Allocation to either control or intervention group by someone not involved in the study, e.g doctor consents patient to partake in trial. Calls up, here is patient x, what treatment are they on. Means surgeon can not switch what the treatment is

Question 3

Double blinding

Answer 3

No one nows what treatment they received until follow up.

Is by definition, concealed allocation

Question 4

EGO and CGO

Answer 4

EGO: Likelihood of a + outcome if you are in intervention group

CGO: risk of + outcome if in comparison group

Question 5

After allocation reasons why patients may not be evaluable

Answer 5

Pull out, no follow up, adverse reaction

Question 6

In example discussed, intention to treat and follow up

Answer 6

In EG and CG, som patients did not receive treatment, so EG and CG could argubaly be the number that actually had surgery, in this instance.
Then some were lost to follow up.

When calculating EGO and CGO, can use Intention to treat, on treatment numbers or those who stayed in study (were not lost to follow up)

Important that if numbers are significant losses, have to be careful what number you use. If you use all EGO’s and CGO’s, compare, if all very close, that’s good/okay.

Rule of thumb, lose less than 20% to follow up, usually okay. However, could be important in a study with very few outcomes, as can change the calculated ‘risk’ between two groups

Question 7

RCT weaknesses

Answer 7

Expensive, usually too small, so lots of random error, usually not ‘real world’ (not for diets), poor compliance (i.e useless for diets)