Re: "Bias in clinical intervention research" : [Letter]

Abstract

In her Journal review discussing the potential biases of controlled trials, Gluud stated that “[t]he purpose of blinding is to prevent bias associated with patients' and investigators' expectations. If interventions are compared with no intervention, an identical placebo may be used. The compared interventions must be identical in taste, smell, appearance, and mode of administration. Any difference may destroy the blinding”. The last sentence of this quotation was based on three references, two of them focusing on vitamin C and common cold trials. However, the Karlowski et al. trial and the Chalmers review were both shown to be erroneous a decade ago.