Use of Placebo Surgery in Controlled Trials of a Cellular-Based Therapy for Parkinson's Disease

Surgical procedures are frequently introduced into general practice on the basis of uncontrolled studies that are less rigorous than those required for the approval of medical interventions.1 The standard for the evaluation of surgical therapy is lower because of the complexity of designing and conducting scientifically valid and ethically acceptable clinical trials of surgical procedures.2 As a result, many surgical trials fail to control for investigator bias or placebo effects.3,4 The list of inadequately studied invasive or surgical procedures that became part of standard medical practice only to be abandoned after closer scrutiny includes bloodletting, routine tonsillectomy, routine circumcision, . . .