Systematic reviews of the effects of healthcare interventions are now quite common. There are currently more than 2 600 full Cochrane reviews in The Cochrane Library, with protocols published for 1 600 more. There are also thousands of systematic reviews published in other journals. However, the science of systematic reviewing is still relatively young. Most of the reviews available today rely on randomised trials, but there are also some reviews of non-randomised trials and of diagnostic test accuracy and these may become more common in the next few years. In this essay, I discuss some of the challenges of doing these newer types of systematic review, and show how experience gained in the last few decades of systematic reviews of randomised trials might help to meet these challenges.
Objective To explore the differences between large and small studies in rare events meta-analysis. Methods Empirical data were collected from The Cochrane Systematic Review Database from January 2003 to May 2018. Meta-analyses with rare events, binary outcomes involving at least 5 studies, and at least 1 large study were screened. Peto and classical ORs were used to compare the magnitude, direction and P-value. Results A total of 214 meta-analyses were included. Among 214 pairs of ORs of large and small studies, 66 pairs (30.84%) were inconsistent in the direction of ORs based on Peto OR (Kappa =0.33), and 69 pairs (32.24%) were inconsistent in the direction of ORs based on classical OR. The Peto ORs resulted in smaller P-values compared to classic ORs in a substantial (83.18%) number of cases. Conclusion There are considerable differences between large and small studies in the results of meta-analysis of rare events.
This paper reports publication status, authors distribution and the difficulties of producing Cochrane systematic reviews （CSRs） in China to offer new ideas for further development of CSR. in China. Up to Dec. 2005, Chinese authors have published 28 CSRs （1.1%）, 10 of which were indexed by SCI.
Objective To assess the effects on labour, maternal, and neonatal outcomes of different techniques and drugs for analgesia during labour. Methods We searched The Cochrane Library (Issue 4, 2006) , MEDLINE (Jan. 1978 to Oct. 2006) and CBMdisc (Jan. 1980 to Oct. 2006) to collect the current best evidence of labor analgesia. Results We included eight Cochrane systematic reviews and six other meta-analyses. The evidence showed that epidural analgesia was associated with a longer second stage of labour, more frequent oxytocin augmentation, higher incidence of instrumental vaginal delivery and maternal fever. But it was unlikely to increase the risk of caesarean section. Conclusion Epidural analgesia is superior to other approaches.
Objective ① To document the way in which allocation concealment is described and coded for studies included in Cochrane Reviews.②To feed back any gaps or miscodings to individual review groups.③ To suggest changes and expansions to advice on how to code and describe allocation concealment methods.Methods The coding and description of methods of allocation concealment for studies included in all 1 596 reviews on issue 1, 2003 of The Cochrane Library are being extracted.So far results are available for 10.8% (173/1 596) of reviews containing 1 844 studies, from 10 Collaborative Review Groups (CRGs).Discrepancies, and inconsistencies with the Cochrane Reviewers’ Handbook, are being documented and analysed.Results The current coding of the adequacy of allocation concealment in studies included in Cochrane reviews is not likely to be very accurate.This is due to failure to describe methods of allocation concealment (38.6% of the sample of 1 844 studies) as well as miscoding (at least an additional 9.2%).The most common method for studies coded A was some variation of envelope use (133/675-19.7% of all A codes). The most common "method" for studies coded B was method unclear or not described in the report of the study (426/665, 64% of all B codes).Conclusions Since adequate allocation concealment is so important in protecting against bias in randomised controlled trials, it needs to be accurately coded and described.We need to improve how this is done for studies included in Cochrane Reviews.Since over half the studies coded as D were likely to have been where reviewers omitted to enter a code, the default should be changed from D to "code not supplied".Structural changes to RevMan are suggested-ideally the addition of a separate new study quality assessment table with fixed headings as well as the facility to enter free text.Suggestions for improving coding in particular reviews will be fed back to CRGs in the next stages of this project.Suggestions for additions to the Cochrane Reviewers’ Handbook are also made.
Until Issue 2 in 2008, the Cochrane Database of Systematic Reviews had included 23 systematic reviews concerning colorectal tumors by the colorectal cancer group. These reviews involved prevention, diagnosis, treatment, prognosis and follow-up. The preventive ability of non-steroid anti-inflammatory drugs, accuracy of chromoscopy, shortterm outcomes of laparoscopic colorectal resection and outcomes of laparoscopic total mesorectal excision were confirmed. Meanwhile, the effect of dietary fibre in prevention, mechanical preoperative preparation, and prophylactic anastomotic drainage was questioned. Because of the low quality of trials, no firm conclusions were revealed in some reviews, such as traditional Chinese medicine in chemotherapy. Through the study of Cochrane systematic reviews, medical practitioners and researchers can obtain high-quality evidence, and identify future research direction in the field of colorectal cancer.
Objective To detect the false-positive results of cumulative meta-analyses of Cochrane Urology Group with the trial sequential analysis (TSA). Methods The systematic reviews of Urology Group of The Cochrane Library were searched to collect meta-analyses with positive results. Two researchers independently screened literature and extracted data of included meta-analyses. Then, TSA was performed using TSA software version 0.9 beta. Results A total of 11 meta-analyses were included. The results of TSA showed that, 8 of 11 (72.7%) meta-analyses were potentially false-positive results for failing to surpass the trial sequential monitoring boundary and to reach the required information size. Conclusion TSA can help researchers to identify the false-positive results of meta-analyses.
Background Tongxinluo capsule is a new drug for cardio- cerebral vascular diseases on the national essential drug list of China, and the second-class award of National Science and Technology Development of China, 2001. Objective This review aims to assess the effect (harms and benefits) of Tongxinluo capsule for unstable angina. Search strategy electronic searchs The Cochrane Heart Review Group specialised trials register,The Cochrane Controlled Trials Register, published in the latest issue of the Cochrane Library, MEDLINE, EMBASE, CBM, Chinese Cochrane Centre Controlled Trials Register, Current Controlled Trials (www. controlled-trials. com), The National Research Register Handsearchs We will search 83 journals of Chinese traditional medicine. Inclusion riteria We will include randomised controlled trials of Tonxinluo capsule versus placebo or other current phamarcotherapy or other Chinese medicinal herbs in the participants with unstable angina pectoris. Studies will report mortality (sudden death from acute myocardial infarction), severity of angina pectoris, frequency of acute attack angina, ECG improvement, rate of dosage reducing or taking frequency of nitroglycerine and symptom improvement, etc. Data analysis Data will be included in a meta-analysis if they are available, of sufficient quality and sufficiently similar.