Effect of investigator bias on clinical trials

Arch Dermatol. 1989 Feb;125(2):216-8.


Two clinical trials were performed to determine the relative efficacy of tioconazole, a new antifungal agent for treating patients with tinea pedis. One study compared the new agent with a placebo cream and the other with miconazole nitrate, an established effective antifungal agent. The investigators found a much higher "cure" rate for tioconazole when both treatment groups were known to receive active agents than the cure rate for tioconazole found in the placebo-controlled study. These results showed that the expectations of investigators can influence their clinical evaluations. Such bias could also influence the results of clinical trials.

Publication types

  • Clinical Trial
  • Comparative Study
  • Controlled Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Antifungal Agents / administration & dosage
  • Antifungal Agents / adverse effects
  • Antifungal Agents / therapeutic use*
  • Clinical Trials as Topic / standards*
  • Double-Blind Method
  • Female
  • Foot Dermatoses / diagnosis
  • Foot Dermatoses / drug therapy
  • Humans
  • Imidazoles / administration & dosage
  • Imidazoles / adverse effects
  • Imidazoles / therapeutic use*
  • Male
  • Miconazole / adverse effects
  • Miconazole / therapeutic use
  • Random Allocation


  • Antifungal Agents
  • Imidazoles
  • Miconazole
  • tioconazole