Do Certain Countries Produce Only Positive Results? A Systematic Review of Controlled Trials
Introduction
The Cochrane Collaboration, an international network of individuals committed to preparing, maintaining, and disseminating systematic reviews of clinical trials [1], has recently established a complementary medicine “field.” This group of researchers has various functions connected with supporting those who undertake Cochrane reviews, such as developing a register of randomized controlled trials, encouraging reviewers who are examining particular health problems (such as back pain) to undertake reviews of trials of complementary therapies, and offering methodologic advice where appropriate.
Because the field wants to promote systematic reviews of acupuncture, we are interested in obtaining data from China; however, researchers have suggested that, for reasons unknown, clinical trials from China always find acupuncture superior to the control intervention. Since this finding would have implications for systematic reviews, we wanted to learn whether it was true. We analyzed the results of trials referenced on Medline as a preliminary means of investigating whether clinical trials originating in any particular country had unusually high proportions of positive results. We are unaware of any similar published study.
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Methods
The study comprised two separate searches and analyses. First, we retrieved and analyzed a set of trials on acupuncture that had been published worldwide. To test hypotheses resulting from this study, we then retrieved and analyzed clinical trials of interventions other than acupuncture that had been published in five specified countries.
The first search, made on Medline (January 1966–May 1995), used “exp acupuncture” as a focus term and “human” and “abstract” as limits. This search strategy
Study 1: Acupuncture
The initial Medline search located 1085 papers of which 252 were eligible for analysis. Overall, 171 trials (68%) were classed as “acupuncture superior to control” and 80 (32%) as “acupuncture equal or inferior to control.”
Acupuncture research was conducted in 27 different countries with the United States (47 trials), China (36 trials), Sweden (27 trials), and the United Kingdom (20 trials) contributing the greatest number of studies. Table 1 presents the raw outcome data for each country.
Discussion
Medline-indexed clinical trials conducted or published in certain countries favor acupuncture over control much more frequently that those conducted and published elsewhere in the world. All 51 trials conducted in China and East Asia and listed on Medline in the period studied favored acupuncture, suggesting that clinical trials of acupuncture originating in certain countries have an unusually high proportion of positive results. One possible explanation for this finding is that acupuncture is
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