How double blind is double blind? And does it matter?

Abstract

In an apparently double blind crossover study, two experienced measurement technicians were able to identify many of the treatment periods. They most often correctly identified aspirin, a drug with prominent effects and side effects. It is argued that in many circumstances it is better to use a blind observer who is not concerned with the giving of treatment or the collection of side effects.

Deleterious clinical effects of transfusion-associated immunomodulation: fact or fiction?

“…Because the diagnosis of nosocomial infections is subjective, observation bias is an important concern, and it may represent an alternative explanation for the findings of some studies and for disagreements among the reported RCTs. 110 Furthermore, the reports of the available RCTs 3-7,22,23 did not present sufficient information about illness severity or the distribution of risk factors for postoperative infection in the treatment versus control arms. 96 In the absence of this information, the possible contributions of selection bias, observation bias, and confounding factors to the reported results cannot be evaluated, and therefore cannot be excluded.…”

Universal WBC reduction:the case for and against

“…Other concerns include the possibilities of selection bias 68,69 and observation bias, 70 which can occur in RCTs and may be responsible for false‐positive results 68–70 . Any system or randomization can be tampered with and compromised, 68,69 making it possible to systematically allocate sicker patients to the treatment group of subjects receiving WBC‐containing ABT.…”

“…Any system or randomization can be tampered with and compromised, 68,69 making it possible to systematically allocate sicker patients to the treatment group of subjects receiving WBC‐containing ABT. Moreover, because none of the hitherto reported RCTs 21,28–31,41,42 have been double‐blind, 70 it is possible that study personnel may have been inclined to diagnose postoperative infection more often in patients from the treatment group than from the control group. Observation bias may have thus been responsible, at least in part, for the disagreements among the available RCTs 67 .…”