We were interested to read the responses to our study on the efficacy of duct tape vs cryotherapy in the treatment of warts. The authors raise several interesting questions about our study design and implications. Drs Buccolo and Moore questioned whether the methods used may have overestimated the treatment effect and whether our study groups had adequate concealment. Given the nature of our study, we were unable to keep the patients blinded to which treatment arm they were in. We attempted to remove observer bias by having multiple clinic nurses measure patients' warts throughout the study. By increasing the number of clinic nurses, we attempted to decrease the probability that a patient would be followed up by the same nurse on return visits. This helped prevent nurses from remembering which treatment arm a patient was in until after they measured the study wart, and therefore helped with concealment. However, the study was impossible to blind completely. We do not think there is adequate data to know if a potential placebo effect of duct tape would be sufficent to bias that study arm significantly.
Focht DR, Spicer C, Fairchok MP. Duct Tape Occlusion for Common Warts: Is Effectiveness Overestimated?—Reply. Arch Pediatr Adolesc Med. 2003;157(5):491-492. doi:10.1001/archpedi.157.5.491-a