Furlan 2006.

Methods	Method of identification of reference standards: cNRSs included in the four development systematic reviews Method of deriving methodological filter terms: analysis of reference standards: two approaches (a fixed method and a progressive method) were used to develop four sets of filters for four development systematic reviews: Fixed method A, Fixed method B, Progressive method (CV) and Progressive method (CV or TW). A quote: "fixed search strategy" was a fixed set of CVs associated with study design. A progressive method (PM) for selection of study design terms was developed and tested: (a) Start with the list of included studies from each systematic review; (b) Randomly select one study from this list and identify it in the database under study; (c) Retrieve the CV (related to study design) associated with the study identified in step (b); (d) Repeat (b) and (c) until a minimum of four CVs was reached; (e) Devise a quote: ‘‘limited search’’ in which the ‘‘topic‐only’’ results were limited to the search terms identified above. The same methodology was applied to identify and test search strategies limited to text words (titles and abstracts)
Data	Years searched for the reference: development set 1966‐2005 (MEDLINE) or 1980‐2005 (Embase) Number of reference standard for each topic:: for combined MEDLINE/Embase in development systematic reviews, 39 cNRSs in endarterectomy, 29 cNRSs in circumcision, 10 cNRSs in methadone, 11 cNRSs in QofL.
Comparisons	Reference standard also contained non‐gold standard records: no Description of non‐gold standard records if used in reference standard: NA
Outcomes	Performance of filters: Sensitivity and Precision (since PPV was calculated in the same way as Precision so that we use Precision instead of PPV) Number of methodological filters developed: 12: Fixed method A, Fixed method B, Progressive method((CV), and Progressive method(CV or TW) for MEDLINE, Embase, and combined MEDLINE/Embase, respectively
Notes	A ‘‘topic‐only’’ search strategy, included only terms related to the population, intervention, or outcomes, but not the terms related to study design. Though it was called "reference standard", it did not serve as the benchmark for comparison but a search strategy without methodological filter Development and validation of methodological filters for identifying comparative non‐randomised studies (cNRSs) in MEDLINE and Embase. Four updated systematic reviews were selected to generate and validate internally the gold standard, topic‐only reference standards, and methodological filters The methodological filters were not validated externally

cNRSs: comparative non‐randomised studies; CV: controlled vocabulary; PM: progressive method; PPV: positive predictive value; PRK: photorefractive keratomileusis; QoL: quality of life; TW: text word