An important task in conducting a systematic review is reading titles and abstracts
of the retrieved references, which often number in the thousands, to determine which
articles meet the predefined inclusion criteria. In the past, this was performed by
manually scanning through large stacks of printed titles and abstracts, followed by
face-to-face meetings to discuss which references should be included. Today, the workflow
of the review process is more streamlined by using computer software.
Several specialized solutions for this process are available, most notably free or
subscription-based online tools such as Covidence, DistillerSR, or Rayyan. The Cochrane
collaboration uses its own tool called ReviewManager. A survey in 2013 showed that
more than half of all systematic reviewers used EndNote software [1]. This dominance
on the market is likely to increase as sales of the second most popular tool, Reference
Manager, have ceased, and its website now advises users to switch to EndNote. Many
reviewers use Microsoft Excel. Some libraries have even created specialized Excel
workbooks to document the process in much detail [2]. A method for the inclusion process
using EndNote is described by King et al. [3], but this process is rather complicated
and time-consuming.
This paper describes the logistics of a method to perform the title and abstract screening,
verdict assignment, and comparisons of results among multiple reviewers in EndNote.
The process is blinded; all reviewers work in their own EndNote files, and after the
individual inclusion and exclusion processes, the verdicts of the different reviewers
are compared. The method described here can be performed much faster than comparable
methods.
THE METHOD
The method consists of several steps. First, a custom style should be installed for
easy abstract scanning. Second, a field should be added to show the reviewer’s name
in the Library window. Third, for each systematic review, custom groups are made in
the EndNote library for included and excluded references. Reviewers drag articles
to the group corresponding to their verdicts. In the last steps for the final comparison
of the verdicts, the included references of all reviewers are combined into one EndNote
library and de-duplicated. References found as duplicates are included by both reviewers
and are selected for full-text review, the non-duplicate references can then be discussed
for inclusion or exclusion.
The steps below are written for EndNote X7 for Windows. EndNote is also available
in a version for Apple Mac computers, but some of the menu items will appear on different
places. The authors have added footnotes that guide Mac users as much as possible.
Step 1: Install the custom-made output style
A custom-made style (named _preview) facilitates easier reviewing of the titles and
abstracts.
Visit http://bit.ly/emcendnote
Open the zip file
Double-click on the file_preview.ens (it will open in EndNote)*
In EndNote, click File > Save As
Remove the text “copy” from the file name, and click Save†
Close the style using the cross in the top right corner‡
To activate the _preview style, open the drop-down menu (called Select Bibliographic
Output Style) in the top left part of the screen (Figure 1)§
Click on Select another style, scroll to the top, select _preview, and click Choose
The abstract of the selected reference will be displayed in the preview tab in the
Tab pane
Figure 1
Activating the _preview style
Step 2: Change the settings of the library window
When comparing the included references between reviewers, a special field will be
used to document the name of the reviewer who included a certain reference. To be
able to view this in the Library window, this field has to be added to the preference
settings.
Go to Edit > Preferences > Display Fields
In column 8 (or an alternative field that is not often used), under Field, select
Custom 4
In the same column, under Heading, type Reviewer
Step 3: Create groups for inclusion and exclusion in the EndNote library containing
the search results
In the first reviewing round, two reviewers independently read titles and abstracts
to decide whether a reference is potentially relevant to the review. We propose the
creation of two group sets: Includes and Excludes, each with, at this stage, just
one subgroup (Figure 2).
Right-click on My Groups, and select Create Group Set
Type Excludes, and hit Enter
Right-click on Excludes, and select Create Group
Type title/abstract, and hit Enter
Repeat the process for Group Set Includes with Includes group
Figure 2
Groups for Includes and Excludes
After the groups for inclusion and exclusion have been made, two copies of these files
are created (adding the name of the reviewer to the file name) and distributed to
the reviewers. All reviewers will work in their own copies of the EndNote file.
Step 4: Title/abstract screening
The standard group named Unfiled contains references not yet assigned to one of the
other groups. When starting the screening phase, the number of references in Unfiled
will be equal to that in All References. Each reviewer reviews the relevance of references
in Unfiled one by one, based on the title and/or abstract.
Broaden the title field in the Library window (Figure 2) by dragging the column break
between the columns of Title and Journal to the right until the Title column reaches
an appropriate width
Review the titles one by one in the Library window until a potentially relevant title
is reached, without yet assigning references to the groups
Click on the relevant title, and read the abstract in the preview tab of the Tab pane
(Figure 2)
If the abstract is irrelevant, continue reading titles in the Library window
If the abstract is relevant, select the article directly above that relevant article
in the Library window, and press Ctrl+Shift+Home to select all references above it.
Drag all of these articles into the Excludes > Title/Abstract group
Next, drag the top reference in the Library window (which is the reference to be included,
as irrelevant references were removed from Unfiled) to the Includes > Includes group
Repeat this process until all references are filed and the Unfiled group is emptied
Step 5: Compare included references between reviewers
Go to the folder Includes in the EndNote library of reviewer 1, and click on one of
the references
Go to Tools > Change/Move/Copy Fields
In Custom 4, select Insert after field’s text, type the first name of reviewer 1,
and click on OK in three pop-up screens
Open the EndNote library of reviewer 2 without closing that of reviewer 1
Go to the Includes group in the library of reviewer 2; select all references in that
group, right click on one of them, select Copy reference to, and select the file screened
by reviewer 1
Go to Window, and select the file by reviewer 1
Go to the Unfiled group, and mark the records in that group with the name of reviewer
2 (as described above in steps 2–3)
Drag the references from Unfiled into the Includes group
Check the settings for de-duplication (Edit > Preferences > Duplicates); at least
Author, Year, Title, and Secondary Title (Journal) should be selected
Go to the group Includes, select a random reference, and go to References > Find Duplicates;
in the detailed comparison screen, click Cancel; then press Delete on the keyboard
to remove the duplicate references
Right click in the group set Includes, select Create a group, and name it Definite
Includes
Select all references in the Duplicate References group, and drag those to the Definite
Includes group
Go to the Definite Includes group, and mark the records in that group with the name
of reviewer 2 (as described above in steps 2–3)
Right click on the Includes group > Includes, and select delete group
Have the two reviewers discuss the articles currently in the Unfiled group
After consensus is reached, drag the references one by one to the appropriate group
until Unfiled is empty
Step 6: Full-text reviewing
In the second round of screening, full texts of the included titles and abstracts
need to be reviewed. Custom groups can be used to distinguish between various reasons
for exclusion, and articles can be assigned to specific groups for certain sub-questions.
All reviewers should again work in their own copies of this library. After reading
all articles, each reference in the library should be discussed in detail; therefore,
no automatic comparison should be used. The steps in this round are more laborious,
differ per research topic, and can hardly be generalized and optimized. Therefore,
we do not describe in detail how this process can be executed.
DISCUSSION
We advise against the use of a “Doubt” or “Maybe” group for articles for which it
is not yet clear whether they should be included. We recommend that in cases of doubt,
the article should be added to the folder Includes. If the second reviewer also has
doubts about the relevance or decided to include the article, the full text should
be used for final judgment. If the second reviewer excludes the article, it is an
item for discussion.
The process of reading titles and abstracts for inclusion and exclusion is often considered
time consuming, and the number of abstracts that can be read per hour is estimated
at 120 by the Cochrane Handbook [4]. A recent study recorded the time needed for certain
steps in the systematic review process [5]. Upon request, the authors informed us
that, using specialized screening software, the median number of articles that could
be reviewed per hour was 68. Another recent study estimated the time needed to screen
1 record based on title and/or abstract at 1 minute [6]. A survey among review authors
at Erasmus MC, to whom we had sent an earlier draft of this article, reported that
the median number of titles and/or abstracts reviewed per hour with the present method
was 308, with a maximum of 675.
We found that the speed of the process increases when reviewers do not document the
specific reasons for excluding references during the title/abstract screening phase.
It is often clear that an article is not relevant to the topic, but to determine the
exact reason (or very often multiple reasons) is very time consuming and unnecessary.
According to PRISMA guidelines, reasons for exclusion, with the number of articles
for each reason, should be given only in the full-text screening phase [7]. We found
that researchers who meticulously documented the reasons for exclusion in the first
round and those who had used other software such as Microsoft Excel reported much
slower rates (median of sixty minutes) and often later regretted their decision to
do so. Also, using specialized programs or online systematic review management systems
such as Covidence or DistillerSR unnecessarily complicate and delay the process because
each abstract has to be assigned to categories individually, in contrast to this method’s
bulk assignment of nonrelevant articles.