Systematic reviews and meta-analyses are widely acknowledged as a key component of the policy and guideline development process 
. A large number of systematic reviews have been published in the area of TB diagnostics 
, and these are increasingly being used for developing guidelines 
. To this end, the Grading of Recommendations Assessment, Development and Evaluation (GRADE) tool has increasingly been adopted by policy makers and guideline developers to provide an explicit, comprehensive and transparent process for moving from evidence to recommendations 
Systematic reviews often conclude by making suggestions for the direction of future research, and thus could be a good source for identifying the most important questions for TB research. Our survey collected descriptive information from all eligible systematic reviews and meta-analyses that were subsequently used to generate a list of research priorities in TB which were used for developing the International Roadmap for Tuberculosis Research 
Our systematic search showed that a fairly high number of systematic reviews were published on TB during the period of 2005 to 2010. The findings of our review need to be interpreted along with a recent systematic review by Rylance and colleagues 
on 33 articles with research agendas on TB. These authors found that the top priority areas for research were new TB drug development (28 articles), diagnosis and diagnostic tests (27), epidemiology (20), health services research (16), basic research (13), and vaccine development and use (13).
In our review of 137 TB systematic reviews, the top three categories for the focus of the research priorities/questions were “Detection, screening and diagnosis” “Aetiology” and “Evaluation of treatments and therapeutic interventions.” TB diagnosis and treatment were among the most important research priorities in both reviews. One possible reason of why TB diagnosis research ranked high on our list could be that our review focused on years 2005 to 2010, a period when major advances have been made in TB diagnostics, especially with IGRAs becoming a very popular subject of research 
. Also, this time period saw the introduction of several WHO policies on TB diagnostics. Further, the emphasis on new tools in the Global Plan to Stop TB 2006–2015 
, along with the creation of product development partnerships such as the Foundation for Innovative New Diagnostics (FIND), AERAS, and Global Alliance for TB Drug Development, may have inspired research on new diagnostics and drugs.
The research priorities determined were mainly focused on the discovery and evaluation of bacteriological TB tests, drug-resistant TB tests and immunological tests, with special focus on IGRA tests. Also, tests for extra-pulmonary TB came up as a frequently cited priority in the Detection of TB category. Other important topics of future research were genetic susceptibility to TB and disease determinants attributed to HIV/TB. Evaluation of drug treatments for TB, drug-resistant TB and HIV/TB were also frequently proposed research topics. Many articles cited the need for improved and tailored treatment methods for MDR-TB and XDR-TB.
Although several systematic reviews identified areas for further research, the questions themselves were often framed in a generic way, rather than in a highly focused manner with specific recommendation for action. Future TB systematic reviews will need to be more focused, and propose highly specific, answerable questions that are amenable to well-designed research studies.
Our study has several limitations. Due to the poor overall quality of reporting of the systematic reviews, the findings may not be representative of the general output from the TB research community 
. The inclusion of eligible studies was limited by the fact that we only reviewed articles in three other languages besides English. We were also unable to search ‘grey’ literature, contact authors, or hand search journals. The review also did not include any unpublished literature. Due to its overarching and generic nature, the Health Research Classification System categories were at times non-specific and difficult to match with specific areas of TB research. Furthermore, it was difficult to classify research priorities into narrow subdivisions since some research priorities could qualify for more than one subdivision. By categorizing research priorities into larger, predefined categories, we lost detailed information on individual research priorities. To remedy this, we condensed each priority and extracted the topic words from it. The topic words were then grouped together to form the summary of repeated priorities/questions and calculate the frequency.
There has been a lot of recent attention and focus on childhood TB, but because our search was last performed in 2010, our analysis may have missed research priorities in this important area.
In summary, our systematic review of published systematic reviews on TB helped identify several key priorities for future TB research. This exercise was useful to describe the landscape of TB research and the overarching TB research themes arising from systematic reviews and meta-analyses conducted over the last 5 years. Their scope is, however, limited, since systematic reviews themselves are influenced by current hot topics or new technologies. They are nevertheless useful in indicating research priorities on areas that receive high attention, either due to recent scientific developments or increasing questions surrounding advancement of knowledge in these very areas. They bring useful additional arguments and information to the broader, deeper and more rigorously conducted process of international research agenda development.