What is already known

• • Search filters, which are single-concept search strategies, are valuable resources used in systematic searches. Common filters include those designed to comprehensively locate literature on a study design or population.

• • Filters are customized for a single database (or rarely, a set of databases) in a single interface, and require translation to be used in a different interface.

What is new

• • This article demonstrates a process for translation of a search filter for the APA PsycInfo database from the Wolters Kluwer Health Ovid interface to the EBSCO Information Services EBSCOhost interface.

• • This article discusses challenges that arise during search filter translation, contextualizing translation processes and decisions with systematic searching principles.

Potential impact for research synthesis methods readers

• • Filter translation is a complex process requiring an understanding of information retrieval principles as well as in-depth knowledge of the database and interface.

• • This article provides a stepwise approach for filter translation while explaining the workings of the various APA PsycInfo database functions on both the Ovid and EBSCOhost interfaces.

2.1 Translation steps overview

1. 1. Verify the original filter’s subject headings.

2. 2. Gather narrower subject headings of any exploded subject headings.

3. 3. Check for revised and/or new subject headings incorporated into the APA Thesaurus since the original filter was created.

4. 4. Add to the search all of the relevant subject headings from steps 1–3, using the syntax of EBSCOhost.

5. 5. For the free text terms, identify and replace the syntax for all search operators, including truncation, wildcards, proximity, phrases, and exact search characters (e.g., preventing stemming or lemmatization).

6. 6. Identify the closest matching metadata fields and field codes for free text strings.

7. 7. Add to the search all free text search strings, incorporating the EBSCOhost syntax for operators and field codes.

8. 8. Combine the final translated search strings.

2.2 Controlled vocabulary search strings

1. Step 1: Verify the original filter’s subject headings.

Verification of subject headings requires the use of the APA Thesaurus. Search each subject heading individually in EBSCOhost APA PsycInfo. Clicking on the subject heading displays information such as the scope note and year of introduction. It also shows its location in the hierarchy, including broader and narrower terms.

In the example below (Figure 1), the subject heading Randomized Controlled Trials is verified, and the information below shows it is narrower than Clinical Trials in the hierarchy, but also has its own narrower term, Randomized Clinical Trials.

• Step 2: Gather narrower subject headings of any exploded subject headings.

Figure 1 Screenshot of the APA Thesaurus entry for randomized controlled trials in EBSCOhost APA PsycInfo showing the broader and narrower terms available.

As shown in the example above, the APA Thesaurus is arranged in a hierarchy, but not all interfaces operationalize that hierarchy in the same way. The Ovid interface offers syntax, called explosion, that automatically includes both a selected subject heading and its narrower terms, all the way to the bottom of the hierarchy. Essentially, the specified subject heading is combined with every single term below it using a Boolean OR construction. The syntax for explosion in Ovid is exp. Thus, a search for exp Randomized Controlled Trials/ in the Ovid interface actually searches for Randomized Controlled Trials/ OR Randomized Clinical Trials/. The slash (/) in Ovid’s syntax, which may or may not be combined with the explosion syntax, restricts the search to a search in the Subject Headings [Phrase Indexed] metadata field.

The EBSCOhost interface’s equivalent to the Ovid slash (/) is the field code DE. There is, however, no equivalent for Ovid’s exp syntax. EBSCOhost handles explosion differently. Checking the Explode box when searching the APA Thesaurus causes EBSCOhost to use OR to combine only the selected subject heading and the subject heading or headings one level below it in the hierarchy. Narrower terms beneath that (such as second and subsequent levels) are not included. In the example below (Figures 2 and 3), the APA Thesaurus displays the narrower term beneath Clinical Trials in the hierarchy, Randomized Controlled Trials. It indicates there are narrower terms in the hierarchy with a + (plus) sign after Randomized Controlled Trials. Checking Explode in the line for Clinical Trials would result in a search for DE “Clinical Trials” OR DE “Randomized Controlled Trials”; it would not include DE “Randomized Clinical Trials,” which is a narrower term under Randomized Controlled Trials.

Figure 2 Screenshot of the APA Thesaurus entry for Clinical Trials in EBSCOhost APA PsycInfo.

Figure 3 Screenshot of the search string generated by EBSCOhost APA PsycInfo when the Clinical trials subject heading is selected and exploded.

Since EBSCOhost does not support Ovid’s explosion approach, it is essential to consult the APA Thesaurus to identify all narrower terms, on all lower levels of the hierarchy, that would be included in an Ovid exp search string.

• Step 3: Check for revised and/or new subject headings incorporated into the APA Thesaurus since the original filter was created.

Controlled vocabulary evolves over time. Existing terms may be removed and replaced with updated terminology or left in place but superseded in new references with that updated terminology. There may also be wholly new additions to the APA Thesaurus. If the filter being translated is a few years old, or if the field of study has evolved or expanded significantly, there may be new or revised terms that should be included in the search. We advise searching the APA Thesaurus and testing the filter with the addition of the new or revised terms.

• Step 4: Add to the search all of the relevant subject headings from steps 1–3, using the syntax of EBSCOhost.

Subject headings are located in a specific metadata field of the bibliographic record, and must be searched using the exact same strings of characters as they appear in the APA Thesaurus. For example, the APA Thesaurus uses Clinical Trials, not Clinical Trial. Capitalization, however, is not important: clinical trials and Clinical Trials, searched with the correct syntax, will retrieve the same results. A field code is the interface-specific syntax that tells it where and how to search that metadata. We go into greater detail about metadata fields and field codes in Step 6.

In the Ovid interface, the metadata field in which subject headings should be searched is Subject Headings [Phrase Indexed], and the field code to search it is abbreviated as SH. The original filter shows the Ovid syntax, which uses either [term]/ or [term].sh. (The period after sh is part of the search syntax.) An example would be: Randomized Controlled Trials/ or Randomized Controlled Trials.sh. which would retrieve the same results. As stated in Step 2, the EBSCOhost interface syntax for the equivalent field is DE “exact term.” The quotation marks ensure that the subject heading is searched exactly as written, with no stemming or lemmatization. Therefore, the EBSCOhost translation for Randomized Controlled Trials/ is DE “Randomized Controlled Trials” [Table 1].

Table 1 Subject heading field code names and abbreviations

In EBSCOhost APA PsycInfo, there are two ways to add subject headings to a search strategy:

To execute the method described in option 2:

Search for each subject heading individually, checking the Select term box to the left when you locate it. As long as you remain in the Thesaurus, the interface will bank all selected terms, regardless of how many searches you perform and where selected terms appear in the hierarchical structure. Thus, you can locate and select all the subject headings for a single concept before moving on to the next step [Figure 4].

Figure 4 Screenshot of an APA Thesaurus search for randomized Clinical Trials in the EBSCOhost interface.

Once you have identified and checked the boxes for all your subject headings for a concept, go to the “Select term” row, just above the Thesaurus. In the Boolean operator drop-down menu, leave OR selected, then click the Add button. Again, even though you cannot see all your selected terms from this view, the button will accurately populate the database search box [Figure 5].

Figure 5 Screenshot of the addition of 4 subject headings to the search screen in EBSCOhost APA PsycInfo.

Click the Search button to add the line to your search history. The screenshot below [Figure 6] shows the Search History after the search is executed.

Figure 6 Screenshot of the search history screen of EBSCOhost APA PsycInfo showing the syntax for a subject heading search.

2.2.1 Special considerations: controlled vocabulary beyond the APA Thesaurus

2.2.1.1 Other controlled fields in APA PsycInfo

In the table [Table 2] below, we list another notable controlled field searchable in both APA PsycInfo interfaces, but which is not part of the APA Thesaurus of Psychological Index Terms. “Controlled” in this context means that there is a specific and finite list of exact phrases used for indexing in that metadata field. A list of all controlled fields and the indexed terms for each can be found in the database’s help pages for the relevant interface. ^{11 , 12} The field in question, Methodology [Phrase Indexed], is available in both Ovid and EBSCOhost. This field does not appear in the worked example in this article but was included in our translation of the All Clinical Trials filter. ¹⁰

Table 2 Methodology field code names and abbreviations

2.2.1.2 One of the controlled fields outside of the APA Thesaurus

Medical Subject Headings (MeSH, the controlled vocabulary subject terms used in MEDLINE) can be found in some APA PsycInfo records. The filters we translated did not include those MeSH terms, likely for multiple factors, including lack of access to the MeSH thesaurus in APA PsycInfo and the lack of a phrase-indexed MeSH field in Ovid APA PsycInfo. Thus, our filter also excludes MeSH.

2.3 Free text term search strings

• Step 5: For the free text terms, identify and replace the syntax for all search operators, including truncation, wildcards, proximity, phrases, and requiring exact characters (e.g., preventing stemming or lemmatization).

Translating a filter as exactly as possible requires finding the closest match for each search operator used in the original filter’s free text search strings. Because not all search interfaces have the same available operators or use the same syntax for the operators they have in common, consulting the help documents for a database on a specific interface is essential. ^{11 , 12} The table below provides details on translation of operators from the Ovid to EBSCOhost interface. One operator issue unique to EBSCOhost, detailed in the table, is “automatic query expansion.” Single words in EBSCOhost must be enclosed in quotation marks to ensure they are searched as that exact string of characters.

2.3.1 Search operator translation table

The following table [Table 3] provides guidance for translating each search operator from APA PsycInfo in the Ovid interface to the EBSCOhost interface.

• Step 6: Identify the closest matching metadata fields and field codes for free text strings.

Metadata fields (sometimes referred to as fields or search fields) are the components of a bibliographic record containing information about a reference. Common metadata fields include author name, title, and abstract. Controlled vocabulary, including subject headings, have their own metadata fields, as noted in Step 4. The metadata fields in a database are typically consistent across interfaces. Field codes are the syntax used by an interface to search metadata fields and are unique to that interface. In a given interface, multiple field codes may search the same metadata field but in different ways; alternatively, a single field code may search multiple metadata fields.

Table 3 Search operator and syntax table for APA PsycInfo database on the Ovid and EBSCOhost interfaces

In free text search strings, specifying metadata fields, and intentionally selecting the field codes with which to search them, serves two main purposes.

First, it allows the searcher to restrict the search for any given concept to fields they deem appropriate or necessary. Not all fields are relevant for all concepts. In EBSCOhost APA PsycInfo, if no field code is specified, an “unqualified search” is performed; this uses a default set of field codes, which include AU, or Author [Word Indexed]. AU searches the metadata fields for author and institutional author. When developing a free text search string for the concept of parks, one might include the truncated term park*. A search for the term park* in a bibliographic record’s title or abstract metadata fields would be helpful, while a search in author name fields would add potentially irrelevant results, often referred to as “noise,” written by an author named Parker. An unqualified search for park* would inevitably introduce significant noise. Thoughtfully selecting metadata fields reduces that noise and thus improves precision. The most common metadata fields to include in a search are title, abstract, and author keyword fields.Reference Lefebvre, Glanville, Briscoe, Higgins, Thomas and Chandler ^{1 ,} Reference Lefebvre, Glanville, Briscoe, Higgins, Thomas and Chandler ¹³ Additional fields that are sometimes considered include journal or source name, geographic region, or subject classification.

Second, specifying metadata fields improves both transparency and reproducibility. Using the example of EBSCOhost’s “unqualified search,” the metadata fields searched differ from database to database (e.g., an unqualified search in APA PsycInfo and CINAHL, both available in the EBSCOhost interface, does not search the same metadata fields or use the same field codes). There is also no guarantee these default fields will be consistent over time. Deliberately selecting metadata fields thus makes it clear which fields were searched and makes it possible to replicate the search in future.

When translating a filter, the aim is to match, as closely as possible, the way metadata fields were searched in the original filter. A database will typically have the same metadata fields regardless of interface, but the available field codes, which determine how that metadata is searched, may differ across interfaces. It’s essential to understand what and how field codes are searching to identify the field codes in the target interface that best match the performance of the original filter.

In the table [Table 4] below, we provide examples of three field codes used in the original Ovid filter that have simple EBSCOhost equivalents. Title is an example where the metadata field being searched by the field code is the same, the field code operationalizes the metadata search in the same way (word-indexed search of the title metadata), and the field code abbreviation happens to be the same (TI). Ovid’s Key Concepts [Word Indexed] (ID) field code searches the same metadata (author keywords) in the same way as EBSCOhost’s Keywords [Word Indexed] (KW), even though the field code names and abbreviations differ. However, when there are significant differences in available field codes, more complex decisions must be made. We address two examples of this in the discussion section.

• Step 7: Add to the search all free text search strings, incorporating the EBSCOhost syntax for operators and field codes.

Table 4 Field code names and abbreviations for title, abstract, and author-keyword fields

Searching using field codes is operationalized differently on the Ovid and EBSCOhost interfaces. In the Ovid interface, field codes are included at the end of a search string. They are preceded by a period (.), followed by the 2-letter field code in lowercase, and ended with a period (.). Ovid will add the final period automatically if a searcher does not include it. Multiple fields can be stacked (that is combined with an OR) in the same search string by separating field codes with a comma. Multiple terms may be used in the same search string if grouped using parentheses. The syntax can be typed by the searcher when working in the Advanced search tab. Alternatively, the field codes can be selected using checkboxes when working in the Search fields tab or individually selected using drop-down menus when working in the Multi-field search tab. The examples below assume the searcher is manually typing the field codes in the Advanced search tab of the database.

For example:

1. 1) To search the word random in the title: random.ti.

2. 2) To search the word random in the title or abstract: random.ti,ab.

3. 3) To search the words random or randomly in the title or abstract: (random or randomly).ti,ab.

EBSCOhost also uses field codes and, as in Ovid, searches can be constructed manually using the two-letter abbreviations in uppercase (e.g., TI or AB). However, the more common approach is to use the Advanced search tab, in which metadata fields are available as drop-down options. Unlike in the Ovid interface, EBSCOhost only allows one field to be applied per line, but Boolean operators may be used to combine multiple lines into what will ultimately be a single search string. Multiple terms may be used in each line. Once the search button is clicked, EBSCOhost translates the query into its syntax, including adding field codes and, as needed, parentheses around search strings.

For example:

1. 1) To search the word random in the title, enter the search string in the box and select TI Title in the drop-down menu; EBSCOhost translates this as TI random

2. 2) To search the word random in the title or abstract, enter the search string in the first box and select TI Title in the drop-down menu, then enter the same search string on the second line and select AB Abstract in the drop-down menu. Finally, select the Boolean operator OR between the two lines. EBSCOhost translates this as TI random OR AB random [Figure 7]

3. 3) To search the words random or randomly in the title or abstract, use the same construction as in example 2, with the search string random OR randomly; EBSCOhost translates this as TI (random OR randomly) OR AB (random OR randomly)

Figure 7 Screenshot of searching the term random in the title or abstract field in EBSCOhost APA PsycInfo.

2.4 Combining search strings

• Step 8: Combine the final translated search strings.

In the case of a filter, all search lines are part of the same concept and are combined with the Boolean operator OR. Both the EBSCOhost and Ovid interfaces provide two options for combining search lines: using checkboxes followed by clicking a button, or manually constructing the search using the interface’s syntax.

In the Ovid interface, the Search History is located at the top of the page. In some cases, you will need to click on Search History to view the content or click Expand at the bottom right of the Search History section to view all search lines. Once all lines are visible, the boxes next to each desired line can be checked. At the bottom center of the Search History area, locate the Combine with: text and click the OR button to combine all selected lines with OR.

The other option in Ovid is to manually construct the Boolean search. Search lines in Ovid are identified by numbers. The syntax to combine lines is line OR line. So, in the case of a four-line search, the search would be: 1 OR 2 OR 3 OR 4. An alternative way of operationalizing this is to use the desired Boolean operator followed by a slash, then followed by the range of search lines separated with a hyphen. The syntax for that is: or/1–4.

In the EBSCOhost interface, the search history can be accessed by clicking the Search History link below the search box or boxes. As in Ovid, you can check the lines to combine, then use the Search with OR button to combine them with a Boolean OR. Unlike Ovid, EBSCOhost uses the letter S followed by a number to identify the search line. So, in the case of a four-line search, the correct syntax would be: S1 OR S2 OR S3 OR S4. This can be typed into the search box in either the Basic or Advanced Search.

2.5 Worked example

Table 5 below shows a line-by-line comparison for the Ovid APA PsycInfo RCT/CCT filter ⁷ translated to EBSCOhost APA PsycInfo. ⁹ The table includes record numbers for each line along with some translation notes. This format allows for comparison of each translated line to the original based on the number of records resulting from each line. Note that small differences between result numbers can be expected due to differences in processing and indexing of records between the two interfaces.

Table 5 Mapped line-by-line translation for the CDA-AMS RCT/CCT filter for APA PsycInfo database from Ovid to EBSCOhost interface ^{7 , 9}