Placebo control subjects receive a similarlylooking treatment which does not contain the study agent, where no-treatmentcontrol subjects receive literally no (i.
e. absence of) treatment. The majordifference between the two designs is that placebo-controlled trials are almostalways double-blind, but blinding of the subjects and investigators areimpossible in no treatment-controlled.The purpose of a control group is to serve as areference and to differentiate outcomes due to the study intervention formthose due to other factors.
“Best available” refers to the evidence produced bya study that has the strongest and most precise methodology on the hierarchy ofevidence. “Gold standard” describes the currently best obtainablemethod or procedure that is supported by sound evidence andbroad consensus; it serves as a guideline which clinician and researchersshould follow. Best available therapy control is currentlyadvocated in the declaration of Heslinki. Use of placebo or no-treatment control group are justifiable when thereis no available proven treatment, when they are supported by validmethodological consideration, and when they pose no extra risk of harm to theparticipant.