Through iterative reading of PILs and following steps of systematic methods developed for deductive content analysis [11–13], we reached a consensus of final three categories by description/explanation of placebo acupuncture: “full disclosure of placebo acupuncture (FD)”, “deceptive disclosure of placebo acupuncture (DD)”, and “missing information on placebo acupuncture (MI)”. The PILs had to use specific words such as ‘sham’, ‘placebo’, or ‘fake’ acupuncture, to be coded in FD category. PILs that used neutral or deceitful words like ‘group two’, or simply the ‘control group’ were put into DD category even though we trusted that the study authors never intended to be ‘deceptive’ on purpose in their PILs. However, if they were followed by additional explanation suggesting that neutrally/deceitfully named group would involve sham procedures (e.g. to receive non-acupoint acupuncture), it was considered to be in the FD category since it was judged that sufficient information was given to the study participants to perceive the existence of placebo acupuncture. For trials with more than one control groups applying different types of placebo acupuncture, each placebo group was counted as a separate unit of data. PILs that missed out on explaining anything about a placebo control were coded into MI category.