Before you expend your energy developing a systematic review, it's a good idea to make sure that no-one else has either already done a systematic review on the topic you've chosen, or is currently engaged in a systematic review on the topic you're considering. Systematic reviews are an enormous undertaking so duplication of effort should be avoided unless there is good reason.
There are a few systematic review registries that you should check:
According to the World Health Organization, the registration of all interventional trials is considered to be a scientific, ethical and moral responsibility because:
Registries checking data as part of the registration process may lead to improvements in the quality of clinical trials by making it possible to identify potential problems (such as problematic randomization methods) early in the research process.
The Campbell Collaboration produces systematic reviews of the effects of social interventions. It is an international social science research network that produces high quality, open and policy-relevant evidence syntheses, plain language summaries and policy briefs. (From their website)
ClinicalTrials.gov is a database of privately and publicly funded clinical studies conducted around the world. ClinicalTrials.gov is a Web-based resource that provides patients, their family members, health care professionals, researchers, and the public with easy access to information on publicly and privately supported clinical studies on a wide range of diseases and conditions. The Web site is maintained by the National Library of Medicine (NLM) at the National Institutes of Health (NIH). (From their website)
The Cochrane Collaboration is an international organization that produces and disseminates systematic reviews of health care interventions. In addition, the Cochrane provides training and support materials, guidelines, and methodologies. (From their website)
The International Clinical Trials Registry Platform is operated by the World Health Organization (WHO). The Platform ensures that a complete view of research is accessible to all those involved in health care decision making. This complete view improve research transparency and will ultimately strengthen the validity and value of the scientific evidence base. The registration of all interventional trials is considered to be a scientific, ethical and moral responsibility. (From their website)
PROSPERO is an international database of prospectively registered systematic reviews in health and social care, welfare, public health, education, crime, justice, and international development, where there is a health related outcome. Key features from the review protocol are recorded and maintained as a permanent record. PROSPERO aims to provide a comprehensive listing of systematic reviews registered at inception to help avoid duplication and reduce opportunity for reporting bias by enabling comparison of the completed review with what was planned in the protocol. (From their website)
Systematic Review Data Repository
The Systematic Review Data Repository (SRDR) serves as both an archive and data extraction tool and is shared among organizations and individuals producing systematic reviews worldwide. This sharing enables the creation of a central database of systematic review data which may be critiqued, updated, and augmented on an ongoing basis. The SRDR is a powerful and easy-to-use tool for the extraction and management of data for systematic review or meta-analysis. It is also an open and searchable archive of systematic reviews and their data. (From their website)