Table 1 Collected variables for the included SRs and references

Collected variables for SRs

 ▪ Number of searched databases

 ▪ Names of searched databases

 ▪ Use of an information specialist

 ▪ Search of reference lists of included studies

 ▪ Use of additional data sources e.g. hand searched journals, key authors

Collected variables for references

 ▪ Recall in searched databases