There remain many questions for further methodological research and for debate amongst qualitative synthesis and meta-ethnography experts that we have started to explore in our review including: what are the defining characteristics (key principles) of a meta-ethnography compared to other synthesis approaches?
These terms were combined one by one, and for each combination, together with the Yale methodological research filter for prognosis and natural history, we calculated the performance characteristics (see online supplementary appendix 1).
As a point of departure, knowing that sufficient efforts have been put into developing a search string for prognosis, we decided to use the Yale methodological research filter for prognosis and natural history to identify prognostic studies.
All in combination with the Yale methodological research filter for prognosis and natural history.
We developed and evaluated a search filter to be used in PubMed in combination with the Yale methodological research filter for prognosis and natural history 14 to identify articles about the prognosis of work disability.
First we checked whether all articles identified by screening the volumes 2008 and 2009 (a total of 40 articles) were included when only using the Yale methodological research filter for prognosis and natural history.
8 In their study on prognostic factors for work ability in sick-listed employees with chronic diseases, Slebus et al 9 used the Yale University's methodological research filter for prognosis and natural history available in PubMed but they did not have a clearly outlined search strategy for disability evaluation to combine with the prognostic filter.
To illustrate the use of our filters for a patient with a specific disease and because search filters behave differently when combined with specific disease terms, we planned to apply both our search filters (WDP-R and WDP-P) in combination with the Yale methodological research filter for prognosis and natural history 14 to the three diagnostic groups.
This implies that evidence in the form of publicly available data from rigorously conducted scientific studies has a moral value in its own right, though the justification is more obvious for effectiveness studies than for methodological research.
There is a moral argument for effectiveness research (Kass 2001), and by extension for methodological research that aims to enhance the validity of effectiveness data by eliminating or controlling biases.
