Selective outcome reporting was defined as “when the full paper publications reported different primary outcomes or changed it from the original pre-defined primary outcome in the registered data.” Inconsistency was defined as “when the items were not the same as described in the registry in the subsequent paper publications.” For the sample size estimation, a discrepancy of over 20% between the registered and published information was judged as inconsistent.
Two authors (MH and X-XL) compared the trial design and methodology from the registered records with the resulting publications to analyse the consistency and selective outcome reporting. 6 We also evaluated the estimated sample size, explicit inclusion and exclusion criteria and the risk of funding bias. 4–6 This tool assesses the following domains: generation of allocation sequence allocation concealment blinding incomplete outcome reporting and selective outcome reporting (defined as change of primary outcome or new outcome added).
We used The Cochrane Collaboration risk of bias tool to evaluate the registered records. We searched for publications in bibliographic databases for those trials listed as ‘completed’ in the registries, and compared the published trials with the registered records. Conditions were classified according to the WHO international classification of diseases ( last accessed 31 July 2012). 11 The extracted data were cross checked by the authors, and any discrepancy resolved by discussion with a third author (J-PL). 10 The main information collected included the number of trials in each registry, year registered, trial design, methods, sample size, setting, participants and diseases/conditions, differentiation of syndrome (bian zheng lun zhi), interventions, controls, primary and secondary outcomes, inclusions and exclusion criteria, current status (eg, completed and ongoing), ethical approval, sponsors, institutions, country of origin, contact details and funding. The form was developed by our research group and based on general characteristics of clinical trials, methodology and the 20 minimum items required for WHO trial registration. Two researchers (from MH, X-XL, Y-JM, Y-YW or G-YY) extracted data independently from each trial registry using a standardised, piloted data extraction form. In order to describe the characteristics of TCM trials, and estimate reporting bias in clinical trials, we systematically searched 15 major international trial registries to identify information about TCM trials, and compared the registered records with subsequent publications regarding outcomes and other data. Furthermore, several peer-reviewed journals such as The Lancet and Trials publish trial protocols to promote transparency and improve trial quality. 8, 9 The WHO established an international clinical trial registry platform (ICTRP ) in 2005, which now links 14 clinical trial registries. One of the ways to improve trial quality is to prospectively register clinical trial protocols in international trial registries such as. 7 Poor-quality trials and risk of publication bias will reduce the strength of evidence when developing clinical practice guidelines or preparing systematic reviews. 1–6 Moreover, publications on TCM trials are uniformly positive, raising concerns that trials initiated to investigate TCM are only published if they have positive results. Many empirical studies have shown that the methodological quality of randomised clinical trials of Traditional Chinese Medicine (TCM) is poor with respect to risk of systematic errors (bias generation of allocation sequence, allocation concealment, blinding, descriptions of drop-out or losses to follow-up, selective outcome reporting) and risk of random errors (play of chance). This may not represent the true situation for trials if the registry data are not updated by the researchers. Subsequent publications were obtained for those studies recorded as ‘completed’ in the registry. The registered information for clinical trials is not uniform across the registries and important methodological information may be missing. Systematic searches of all available international trial registries for any clinical trials of TCM.Īll interventions involving any TCM were included as was the diagnosis.