Fig. 3

Reporting rate of each item.17 reporting items were used for statistical analysis. The 13 items from the bottom up are the TIDieR-placebo checklist. a (Brief name) We counted all trials that provided the name of the placebo used by the control group, including the name “placebo”. b (Why) We accounted for all statements of reasons for the use of placebos, which reached 100% as stated in the purpose of the trial. c (What) We refer to the official example of TIDieR, and the studies we included did not have eligible procedures. d (Where) We analyzed the data by country or hospital. e (When and how much) For this item, we counted drug doses for each trial. f (Modification) If the placebo was modified during the course of the study, describe the changes. g (How well, actual) If adherence or fidelity was assessed, describe the true situation. 8 (16%) trials [6, 18, 29,30,31,32,33,34] did complete reporting for the composition of the placebo. 10 (20%) trials reported that who provided placebos. 7 (14%) trials [16, 28, 31, 35,36,37,38] described the modes of delivery. 7 (14%) trials [18, 28, 30, 33, 39,40,41] described strategies to maintain or improve adherence. 23 (46%) trials showed that the placebo was physically identical to experimental HM, but one trial [42] the placebo was checked by a pharmacist to make sure the placebo was physically identical to experimental HM. Moreover, a trial [6] that used the same coating for the drugs, which can effectively avoid the failure of trials caused by dissimilarity. The safety assessment includes safety testing of raw materials and health testing of subjects. Only 3 (5.5%) trials [27, 30, 31] have controlled placebo raw materials, and they include microbial limits and certificates of quality. The commonly used safety tests of subjects include routine blood, urine, stool, liver function, renal function, blood test, ECG, and adverse reactions. None of the trials performed a pharmacological inert test of the placebo, even though some of the placebos used the experimental HM. More detailed information is shown in Additional file 2: Table S1. We have also translated the abstracts of the studies published in Chinese and can be found in Additional file 3